# Battery self discharge due to car fault?



## WobblyHand (Sep 20, 2022)

For what is the third time, my 2015 Subaru Legacy battery has self discharged.  It doesn't happen super often, but it is a pain in the neck.  Found out this morning that my battery was flat, when I had an eye doctor appointment.  Borrowed my wife's car and went to the doctor.  As far as I can tell, it isn't me.  I didn't leave a door ajar, or the trunk open.  The last time this happened (last year) I had the battery tested and the battery company said the battery itself was good, despite its age, it was just discharged.  They said I did not need to buy another one!  The alternator seems to check out.  I suppose I should check the diode pack, if I could access it.

I tested the battery and it was discharged to 3.75V!  I have it on a "smart charger", set at 4A.  It seems to be charging, at least I can see the battery voltage slowly climbing upwards, albeit at a slow rate.  Don't want to go on fast charge just yet, as I'd like to see if the battery takes some more charge first.  Don't want to boil away the electrolyte.  I did check one of the battery caps, the three holes had adequate fluid.

There is a TSB 11-174-17R on this sort of thing.  The TSB addresses 3 issues, one of which is "Dead battery after repeated periods of short-trip driving".  There's claims (on the internet) that the fault is a bug in the CAN bus software, where the CAN modules are, under some circumstances, not told to go asleep.  If they don't go asleep, then the modules draw a lot more power, draining your battery dead in no time.

This is a classic intermittent problem.  Anyone got an idea on how to "cheaply" capture the issue?  Batteries are rather expensive these days.  

Anyways, this is yet another reason I don't like this vehicle...  Basically, it's no fun anymore.  I'd buy something else, but now's not a great time to be car shopping.  Maybe in another year or two the offerings will be more attractive.


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## DavidR8 (Sep 20, 2022)

3.75V is a very deep discharge. 
If you are able to bring it back to full charge, I'd leave it out of the vehicle and hook a good multi-meter up to it to monitor the voltage throughout the day. See how the voltage plots over the day.
Then stick it back in the car and do the same thing. 
I assume you haven't had it in for the TSB work?


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## WobblyHand (Sep 20, 2022)

DavidR8 said:


> 3.75V is a very deep discharge.
> If you are able to bring it back to full charge, I'd leave it out of the vehicle and hook a good multi-meter up to it to monitor the voltage throughout the day. See how the voltage plots over the day.
> Then stick it back in the car and do the same thing.
> I assume you haven't had it in for the TSB work?


No, just found the TSB.  Not sure if the TSB really fixes the bug.  Car dealers/manufacturer's are reticent to reveal bugs and their fixes.  They don't want to provide any information, for fear of law suits and stuff.


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## wachuko (Sep 20, 2022)

Tracing battery drain causes on your own is a PITA...  

We had a 2018 Subaru Crosstrek until last month, and we had to make sure we did not leave the trunk light on.  It is separately switched... so unless you manually turned it off, it would slowly drain the battery... even after replacing the light bulb with an LED alternative.


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## wachuko (Sep 20, 2022)

WobblyHand said:


> No, just found the TSB.  Not sure if the TSB really fixes the bug.  Car dealers/manufacturer's are reticent to reveal bugs and their fixes.  They don't want to provide any information, for fear of law suits and stuff.


I joined a Subaru forum... that helped a lot with sharing findings...  Good thing you found that TSB... but not a recall, so will they charge you to fix it??


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## WobblyHand (Sep 20, 2022)

wachuko said:


> Tracing battery drain causes on your own is a PITA...
> 
> We had a 2018 Subaru Crosstrek until last month, and we had to make sure we did not leave the trunk light on.  It is separately switched... so unless you manually turned it off, it would slowly drain the battery... even after replacing the light bulb with an LED alternative.


Pretty sure that the trunk light turns off by itself, but that's something to check.  I know that there's an override to turn it off, I can make sure it's off.


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## rabler (Sep 20, 2022)

Don't know if your Subaru has a keyless entry/start system, but my father claimed his Subaru would drain the battery if the wireless key fob was left in/near the car (perhaps related to that TSB?).  He is in a very remote location so it is routine for them to leave the keys in the car at home.  He resorted to a conductive envelope to shield (i.e. faraday cage) the key when it is left in the car.


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## WobblyHand (Sep 20, 2022)

wachuko said:


> I joined a Subaru forum... that helped a lot with sharing findings...  Good thing you found that TSB... but not a recall, so will they charge you to fix it??


I never got paid back by Subaru for a TSB that turned into a recall.  They conveniently forgot about that.  I got it fixed while it was a TSB, because I didn't care for gasoline leaks...


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## WobblyHand (Sep 20, 2022)

rabler said:


> Don't know if your Subaru has a keyless entry/start system, but my father claimed his Subaru would drain the battery if the wireless key fob was left in/near the car (perhaps related to that TSB?).  He is in a very remote location so it is routine for them to leave the keys in the car at home.  He resorted to a conducive envelope to shield the key when it is left in the car.


That happened to my wife.  Left key in car overnight and it drained the battery.  We went to the store and couldn't start the car to get home.  Of course, we were on vacation.  We bought a jumper cable set and got a jump from someone.

My key is usually in my pocket.  Bedroom is pretty far from the car, though I could try that conductive envelope trick.  Wouldn't cause harm.


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## markba633csi (Sep 20, 2022)

Trunk light and glovebox light are sometimes culprits- but the canbus issue sounds likely too.
Only way to find it is to check the current drain when the car is off, but it's a pain since you can't easily put the meter in the non-starter leg of the system- maybe at the fuse box you could make a "fake fuse" and do it there
I believe a normal off-state draw is 50 milliamp or less (0.05 amp)


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## pdentrem (Sep 20, 2022)

Easy to test the car and battery. Continue charging the battery until done. Let sit overnight and recheck voltage. Still good or down? If still good place in the car and only connect the positive cable and place an amp meter between the negative cable and the negative post on the battery. Likely will see a high reading on first contact but should drop down to well under 0.09 of amp.


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## WobblyHand (Sep 20, 2022)

markba633csi said:


> Trunk light and glovebox light are sometimes culprits- but the canbus issue sounds likely too.
> Only way to find it is to check the current drain when the car is off, but it's a pain since you can't easily put the meter in the non-starter leg of the system- maybe at the fuse box you could make a "fake fuse" and do it there
> I believe a normal off-state draw is 50 milliamp or less


Finding parasitic currents is hard.  Don't think there's a single fuse for all of the CAN peripherals.  For that matter, I think most vehicles these days have multiple CAN buses.  Probably the best one could do is to monitor the non starting power dark current.  I only really want to catch it, if it doesn't power down.  Most times CAN turns off properly, except when it doesn't!

To make such a device would require it be powered from the vehicle and it would be able to log data.  Bonus points if it texted me if the dark current was greater than x, y minutes after key off.  I don't know how long a proper shutdown/sleep takes, but I suppose a logger would tell me that.


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## brino (Sep 20, 2022)

1) Just beware that with most recent vehicles there are a ton of electronic modules that may draw power for a surprisingly long time after you turn off, lock and walk away. On a Jeep I remember the service manual claiming an Ignition-Off Draw (IOD) of ~50mA, however I found that after you open/close a door the body-control module (BCM) was pulling more that that for about 1/2-hour before the current really dropped to ~50mA.

2) My wife's 2015 Forester has some emissions thing that runs for a few minutes several hours after it is parked. There is noise with it, from under the vehicle near the back end; a motor driving a valve maybe...... The first time I hear it, I was concerned about what was going on. I looked it up and did see this was a known emissions cycle. I heard it again last night when I had the dog out for a walk.

3) It is a PITA workaround, but you can get whole-car on/off switches that you mount to the battery post:
https://www.princessauto.com/en/top-post-battery-master-cut-off-switch/product/PA0004210962
https://www.princessauto.com/en/12v-dc-battery-side-post-knife-blade-switch/product/PA0008512543
https://www.princessauto.com/en/12-24v-rotary-battery-master-switch/product/PA0008437402

As mentioned a PITA, but if it saves you from being stranded.........

Good Luck!

Please let us know what you find.

Brian


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## WobblyHand (Sep 20, 2022)

pdentrem said:


> Easy to test the car and battery. Continue charging the battery until done. Let sit overnight and recheck voltage. Still good or down? If still good place in the car and only connect the positive cable and place an amp meter between the negative cable and the negative post on the battery. Likely will see a high reading on first contact but should drop down to well under 0.09 of amp.


My belief is that this is not a consistent problem.  It only occurs once or twice a year.  So the instrumentation has to be in place, measuring for months or a year before it would catch it.  It's also not easy to measure currents over a large span, from 100's of amps to 0.1 micro amps.  I think if I were to break the ground connection to measure it, the power interruption would change the problem.  However, once the battery is charged, and the car is off, I will check the leakage current, because it's another data point.  Maybe it's a mechanical or simple wiring fault.  That would be nice, better than diagnosing CAN bus issues.


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## WobblyHand (Sep 20, 2022)

brino said:


> 1) Just beware that with most recent vehicles there are a ton of electronic modules that may draw power for a surprisingly long time after you turn off, lock and walk away. On a Jeep I remember the service manual claiming an Ignition-Off Draw (IOD) of ~50mA, however I found that after you open/close a door the body-control module (BCM) was pulling more that that for about 1/2-hour before the current really dropped to ~50mA.
> 
> 2) My wife's 2015 Forester has some emissions thing that runs for a few minutes several hours after it is parked. There is noise with it, from under the vehicle near the back end; a motor driving a valve maybe...... The first time I hear it, I was concerned about what was going on. I looked it up and did see this was a known emissions cycle. I heard it again last night when I had the dog out for a walk.
> 
> ...


Yes, there's a normal shutdown cycle for these modern vehicles.  I will have to research what the normal times should be.

Master switches are great for airplanes and racecars, but not so good for normal vehicles.  I've heard, but don't know for sure if total power removal affect emissions.  The engine may have to be driven a bunch to properly set the codes.  This could matter if you are up for your annual emissions check.  Don't know that for a fact, perhaps it's all hearsay.  We all know that there's a lot of baloney on the internet!  Modern technology should be able to withstand battery removal without affecting emissions, but it doesn't mean that the car manufacturer has installed that in your ECU, for your model year.


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## rabler (Sep 20, 2022)

WobblyHand said:


> My belief is that this is not a consistent problem.  It only occurs once or twice a year.  So the instrumentation has to be in place, measuring for months or a year before it would catch it.  It's also not easy to measure currents over a large span, from 100's of amps to 0.1 micro amps.  I think if I were to break the ground connection to measure it, the power interruption would change the problem.  However, once the battery is charged, and the car is off, I will check the leakage current, because it's another data point.  Maybe it's a mechanical or simple wiring fault.  That would be nice, better than diagnosing CAN bus issues.


You can get DC clamp ammeters, basically a hall effect device.  This would allow you to not interrupt the circuit and still make measurements.  But using that over long term is probably still not practical.  Build yourself an arduino based hall effect current meter/logger?  You probably only need to accurately measure currents <1amp, and note times with higher current.


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## WobblyHand (Sep 20, 2022)

rabler said:


> You can get DC clamp ammeters, basically a hall effect device.  This would allow you to not interrupt the circuit and still make measurements.  But using that over long term is probably still not practical.  Build yourself an arduino based hall effect current meter/logger?


That's where I'm headed!  I need another project for something like this, like I need a hole in my head.  Measuring current over 6 decades isn't that easy, though.  Technically I really don't need to measure 300A cranking current, but I need the device to be able to survive cranking and be able to detect say 100 microamps.  Interesting problem, especially over temperature.


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## rabler (Sep 20, 2022)

WobblyHand said:


> Technically I really don't need to measure 300A cranking current, but I need the device to be able to survive cranking and be able to detect say 100 microamps. Interesting problem, especially over temperature.


Old cars (i.e., 1970's) used to have a split pretty quickly between the starter and everything else.  Not sure how newer vehicles are wired, but you could at least look at measuring downstream of where the starter main is tapped.  Pretty safe assumption that the starter isn't the issue.  Many of the LEM brand hall effect sensors I'm familiar with note absolute max current around 20x the max measurable ...


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## Aukai (Sep 20, 2022)

This is what I remember from long ago when I was chasing battery draw. This is how I remember it anyway.
Put one probe on the bat neg, one on the block, if there is a current draw showing, I pulled fuses one at a time to determine the circuit/source. Then follow the schematic, mine was a light socket, the bulb was off, but the socket was drawing some power.


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## WobblyHand (Sep 20, 2022)

Battery so far seems to be charging, although I don't know how healthy it is.  Up to a whopping 9.8V, we are almost to a dead battery!


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## Jake M (Sep 20, 2022)

WobblyHand said:


> Battery so far seems to be charging, although I don't know how healthy it is.  Up to a whopping 9.8V, we are almost to a dead battery!


Reply

Subarus don't like old batteries, even if they seem  OK.  At work we don't even test 'em after 4 years.  The labor involved far exceeds the value of the extra year that "might" be still in the battery, and there's still no guarantee that the test is gonna catch what makes Subaru's grumpy, which is essentially too quick of a voltage change in too short of a time.  

That said...  You're not in retail, so costs and expectations are different.  How long has it been on the smart charger to get to that 9.8 volts?  Do you have any of the ratings from the battery?  (Cold cranking amps, cranking amps, reserve capacity).  How old is the battery?  Does this car have passive entry, or must you push the button on the remote to unlock it?  Starlink?  Does your volt meter have the ability to capture min/max voltages?  Do you by chance own an inductive ammeter ("amp clamp") that can read DC amps?  Doesn't have to be automotive related, if it'll read ten amps at half an amp resolution, but it can not be invasive, can't be wired in series.)

It doesn't mean as much in the beginning, but all (or at least most) of those use a group 35 battery, so maybe kinda like 600 cca, 100 minutes?  If you get the chance to pay attention, once you get to 12.3 or pretty close, at four amps, I'd want to see it take a solid six hours to hit a full charge.


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## great white (Sep 20, 2022)

I’ll ask a simple question that hasn’t been asked yet: factory radio or aftermarket replacement?

aftermarket radios are notorious for parasitic drain.

To test the battery, you need to have it load tested. Voltage reading will only tell you if it will reach spec’d voltage, not how much capacity the battery has left. They all drop some voltage when off the charger, a load test will tell you if it still has enough capacity to start and run the car.

Charge it up and take it to an autoparts store. Most have a battery load tester and will do it for free. A modern lod tester can even tell you if a single cell is weak or about to fail. They do it for free mainly because if it tests bad, they assume you will buy a new battery from them.

Don’t rig up a battery disconnect on a modern car. The ecm/pcm in modern cars has a learning algorithm. It learns as you drive the car and tailors things like transmission shift points to better match how you drive. Every time the battery is disconnected for an extended period, the data in the volatile memory is lost and it has to go though the learning cycle all over again. As also mentioned, it will muck up the “ready” status of your emissions controls and will fail a smog test, if you have to have one where you live. They will go back to “ready” eventually, but it’s always reliant on things like number of starts or miles driven. To get back to ready status, you have to drive (or start) past the specified criteria for the emissions modules to switch to “ready”.


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## WobblyHand (Sep 20, 2022)

Battery charged to 13.5V.  Was on charge since 11am, so 6 hours, but at 4A.  When I pulled the charger, the battery voltage was 12.8V or so.  I was able to start the car and run it at high idle for 30 minutes.  Was able to able to shut everything down.  Hopefully it will hold well enough overnight.  Tomorrow I can put it on charge again.  Maybe I can set it to 8A then.  I will not leave it on 8A overnight.  2A, yes, but not 8A unattended.



Jake M said:


> group 35 battery, so maybe kinda like 600 cca


I would have to check, but this is the second battery, and it was upsized, at Interstate Battery, at my request.  Don't remember the size.  It was big enough I had to fabricate my own clamp, because the stock one was far too small.  Last year, when this happened, I went to Interstate Battery and bought a new battery.  But before installing it, I mentioned the discharge problem.  The guy went out to my vehicle and performed some tests and told me I didn't need a new battery, and he issued me a refund.

Yes there is Starlink, although, I have never even used it.  My meter can capture max and min.  I do not have the inductive clamp for the ammeter, only an inductive pickup for spark.  I'm not sure if this is what you call passive entry.  When you get close to the car, some leds on the side view mirror come on.  If you touch the handle, then it will unlock for you, at least on the drivers side.


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## WobblyHand (Sep 20, 2022)

great white said:


> I’ll ask a simple question that hasn’t been asked yet: factory radio or aftermarket replacement?
> 
> aftermarket radios are notorious for parasitic drain.
> 
> ...


Factory radio.  I'm too smart to install an aftermarket radio anymore.  They are a royal PIA to do.  But, of course, in my youth, I did a few.  Not anymore.

Yes, I really need to get it load tested.  I will give Interstate a call, since they did me a kind turn.

The real test will be in the morning.  We shall see what is remaining in the battery.


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## great white (Sep 20, 2022)

An “oversized” battery is not always a good idea.

The thing is, the oem charging system is designed to charge the original battery and run the electronics in the car and thats about it. Oem’s design to the bare minimum (ie: $$$), so the oem charging system is going to take longer to fully charge a bigger (capacity) battery. More so if you’re only making short trips.

Now that I’m retired, I’m lucky if I put 5-10k kms on my truck in a year. Even less on the Corvette (which is an absolute parasitic loss _monster, _needs a recharge weekly). To make it worse, its almost all short local trips. That all adds up to bad news for battery life. Mainly because a lead acid battery sulfates if left in a lower charge state for too long and that will cause the plates to short. So what I do is put a 2 amp smart charger on it once a month, just to keep the battery healthy and help stave off sulfation. Like your subaru, my 2016 has more modules than you can shake a stick at and is always drawing some level of power from the battery.

Also to consider is most vehicles need to get above 2000-2500 rpm before they make any significant amps to recharge the battery. Running it at high idle for 30 mins probably put very little charge back into it. For the alternator to charge a low battery it needs to hit the highway for an hour of two.

Depending on how new the car is, the ecm/pcm often controls alternator output and it knows when youre sitting still or putting a load on it and it excites the feild coils accordingly….


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## pdentrem (Sep 20, 2022)

You are right about high idle does minimal charging. Highway speeds like you stated will do the job.
At the shop we would only idle to check operation of the alternator and do a field test by shorting out the regulator on the back. Cannot do this these days! When GM went to the small sized units back in the mid 80s, the real troubles started! They cannot put out over 100 amps at idle without burning out. Hot summer temperatures with AC and the engine cooling running in slow in town speeds were killing dozens a week just in our small town. We dealing with ****** off customers etc, was not fun.


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## ChazzC (Sep 20, 2022)

My wife’s 2019 Trax’ battery died a couple of weeks ago and I learned a couple of things:

1) If you leave it in gear and turn off the engine, all of the other systems stay on. Doesn’t need to be much out of Park, so it’s a common issue.

2) Couldn’t get in once the battery was dead until the tow truck driver showed us the key that’s hidden inside the “keyless” fob - something the dealer forgot to tell my wife when she took delivery.


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## WobblyHand (Sep 20, 2022)

great white said:


> Also to consider is most vehicles need to get above 2000-2500 rpm before they make any significant amps to recharge the battery. Running it at high idle for 30 mins probably put very little charge back into it. For the alternator to charge a low battery it needs to hit the highway for an hour of two.


You are right.  I'll take it out on the road for a bit tomorrow, after I charge it in the morning.

Decided to put it on trickle charge overnight.  You know, so at least it won't be dead by the morning.


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## great white (Sep 20, 2022)

pdentrem said:


> You are right about high idle does minimal charging. Highway speeds like you stated will do the job.
> At the shop we would only idle to check operation of the alternator and do a field test by shorting out the regulator on the back. Cannot do this these days! When GM went to the small sized units back in the mid 80s, the real troubles started! They cannot put out over 100 amps at idle without burning out. Hot summer temperatures with AC and the engine cooling running in slow in town speeds were killing dozens a week just in our small town. We dealing with ****** off customers etc, was not fun.


Oh yeah brother, and when it comes to being p-d off, Quebec-ers know how to do it right!

(j/k)

Seems like pretty much anything Quebec-era do, they go “all in”. Lots of intensity, lots of emotion lots of determination.

I remember the Van Doos (le Vingt-deuxième) being the “hunters” on my survival and escape course. Those guys were nuts! No quitting, no quarter. They didn’t catch me, but they sure didn’t make it easy and it was misery staying out of their grasp. The giys that did get caught were put through torture techniques (like you would if caught behind lines) and after hearing what they went through, being cold, wet and mildly hypothermic for 4 days was worth not getting caught.

Unfortunately, since I was one of only two guys they didn’t catch, the instructors decided we needed to be waterboarded so we would know what torture was like.

It was only training and I knew they wouldn’t actually hurt me (on purpose), I was close to telling them whatever they wanted to know. Lies or not, didn’t matter, I just wanted out of that wet burlap bag.

To this day, the instructors and rcmp have no idea how I got away from the dogs and the FLIR….and I’m still not talking!

LOL!


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## tq60 (Sep 20, 2022)

What you need is an always installed instrument.

Go yo Amazon and search for shunt ammeter

There are many options.

Here is a unit we made for monitoring battery chargers, we have 12,24 and 36 volt systems and this shows both voltage and current.

The direction matters for current, it only works one way so it can show charging or discharging.

A toggle switch could easily reverse the sens wires to allow switching between.

You install the shunt in line with the ground cable.

Ours has 5 wires, 2 wires for ammeter go to the shunt to measure current.

One wire from voltmeter also goes to shunt for ground then the other 2, power and voltage measure go to hot.

You can use a 9 volt battery to power the voltmeter as option.

There may be data logging ones too
Sent from my SM-G781V using Tapatalk


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## Jake M (Sep 20, 2022)

WobblyHand said:


> Battery charged to 13.5V.  Was on charge since 11am, so 6 hours, but at 4A.  When I pulled the charger, the battery voltage was 12.8V or so.  I was able to start the car and run it at high idle for 30 minutes.  Was able to able to shut everything down.  Hopefully it will hold well enough overnight.  Tomorrow I can put it on charge again.  Maybe I can set it to 8A then.  I will not leave it on 8A overnight.  2A, yes, but not 8A unattended.
> 
> 
> I would have to check, but this is the second battery, and it was upsized, at Interstate Battery, at my request.  Don't remember the size.  It was big enough I had to fabricate my own clamp, because the stock one was far too small.  Last year, when this happened, I went to Interstate Battery and bought a new battery.  But before installing it, I mentioned the discharge problem.  The guy went out to my vehicle and performed some tests and told me I didn't need a new battery, and he issued me a refund.
> ...



After sitting overnight, see what the battery voltage is.  As found, before you start the car, thoroughly rested....  "Everybody" is going to wake up and start computing things just as soon as you open the door to open the hood, but if you can get a measurement within a few minutes, it'll be valid.

If it's lower, but not dead, I'd be a lot happier. Shooting from the hip, generalizing...  above 50 or 70 percent maybe.  Low twelve forties.   I don't think it should be charged as much as it is, this soon, with that low of a charge rate.  But that information tomorrow will be more solid.  I'm looking for insight into the capacity here.  If you put four gallons of water into a five gallon bucket, and it's full...  You can kinda figure that some part of the storage area inside that bucket was occupied with something else, and not available for storage.  Or if that bucket takes a whole five gallons to fill, you can safely assume it was probably empty.....

When you have that battery rested and steady at 12.5 or better (well charged, but need not be "perfect",  set the volt meter across the battery terminals, set the min/max to catch the minimum, it'll record where the voltage pulls down to when you first engage the starter.  That is when the battery is delivering the "inrush" current to a "stalled" motor,  with that rested battery and a stone cold engine.   This goes to the battery's ability to discharge, or deliver current.  Not knowing how upgraded the battery is, I'm going to say that high 9.6 range and up is a pass.  Technically it goes WAY lower than that in the best of cases, but it's only just a bit more than instantaneous, so if your result is low, toss up the make/model of your volt meter.  I can google that right quick and get a sample rate for that meter (unless you happen to know it....), and do a rationality check on the reading.

As for the inductive ammeter, that test would have gone to the "maintenance current", which is how many amps are going through the battery after it is fully charged, and not actually accepting any more charge.  Usually (....usually....) the electronic testers such as I'm sure an Interstate dealer was using do a good job extrapolating that.  In short, it tests the internal resistance of the battery.  Which is a great test, but unfortunately it's one of those things that can be intermittant.  At a few times a year....  I wouldn't run out and get one.  If you had one there's a chance you could catch an intermittant.  If you don't have one, there's an even better chance you could totally miss the problem, even if it were real and the actual root cause of your issues.

With the Starlink, it's been known to sometimes just wake up and start trying to call up the mother ship.  If it's been unused all along though, there's probably nothing set up that would have been triggered.  Do you have any random or intermittent check engine lights at or near these dead battery occurrences?  It does (I believe) phone those in for statistical purposes, even if you're not signed up to do anything about it.  That system gets grumpy sometimes if nobody at the other end answers.  But not always.  Not sure how it determines to keep trying or to give up and try later.  But if nothing with that starlink has changed since times were good, and check engine warnings don't coincide....  I'd probably not put this high on the list.

Your description of the locks is indeed passive entry.  Keyless entry is when you have a button on the key, remote, etc that unlocks the door.  Passive entry is when the car and the key are always in communication, so it knows the proximity of the key, so it will allow you to unlock without so much as touching the fob.  That is an "always on" communication there, any time a key is in range.  Subaru is not the worst in that case, but there can be issues.  A key left inside the car is probably fine.  (It knows where the key is for starter interlock purposes).  Outside the car, multiple keys in range can get weird, (although, if it's always been.....  nothing will really "develop" here).  Or one or both keys with low batteries.  That can be a one time thing.  Another is if you have a "less used" second or other extra key, where the car has been started enough that the rolling codes have diverged.  They'll catch up and reset  if you carry one into the car and use it to start the car, but for passive entry, they can go nuts with the challenge and response thing they use to "stay in tough...  So if an less used key/fob is randomly left in close enough proximity to communicate (but not inside the car), that can keep everybody awake when they're supposed to be turned off.  So really, in that department, I'd look for anything that has changed.  Battery gone dead coinciding (somewhat) with the events, spare key left out, not where it usually is, that sort of thing.


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## WobblyHand (Sep 20, 2022)

Jake M said:


> After sitting overnight, see what the battery voltage is.  As found, before you start the car, thoroughly rested....  "Everybody" is going to wake up and start computing things just as soon as you open the door to open the hood, but if you can get a measurement within a few minutes, it'll be valid.
> 
> If it's lower, but not dead, I'd be a lot happier. Shooting from the hip, generalizing...  above 50 or 70 percent maybe.  Low twelve forties.   I don't think it should be charged as much as it is, this soon, with that low of a charge rate.  But that information tomorrow will be more solid.  I'm looking for insight into the capacity here.  If you put four gallons of water into a five gallon bucket, and it's full...  You can kinda figure that some part of the storage area inside that bucket was occupied with something else, and not available for storage.  Or if that bucket takes a whole five gallons to fill, you can safely assume it was probably empty.....
> 
> ...


Before you posted, I went outside to install the trickle charger (2A max) for an over night charge.  The charger showed the charge was on the low side, but who knows what those idiot lights mean exactly.  I think the charger claims the battery is only 1/4 charged.  

I have no idea what the sampling time is of my volt meter.  It is an Innova 3340A.  I use it as a guide.  It's ok for slow moving stuff.  If I want to measure transients, I use an oscilloscope.  Unfortunately, I do not have any current probes.

I have not had any random or intermittent check engine lights.  There was no notice of this.  The battery was fine 3 days ago.  It started without hesitation and nothing seemed amiss.  No dim lights, no malfunctioning electronics.  I have experienced that in other vehicles.  I drove somewhere and came back.  I hadn't used my car for three days, so I was surprised that the battery was so flat.  No keys were left in the car, or near the car. The closest key was in a cabinet about 50 feet away, through a garage and a house.  All key fobs have had their batteries changed within the last three or four months.


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## RandyWilson (Sep 20, 2022)

The TSB is for a reflash to change the charging system strategy. Your symptoms don't match that. The P05A0 code that it also addresses is a possibility, though. If the grill louver can't close on power down, and doesn't have a time-out in the control, that might well take the battery out. The same thing could happen with various HVAC doors that are closed on power-off.

Even if the CAN bus sleep call doesn't happen, the computers are going to shut down well before pulling the battery down the 3.xV. Usually Hitachi systems give up at around 8.5V.


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## mattthemuppet2 (Sep 20, 2022)

If it only happens once or twice a year, it would probably be easier and cheaper to spend $100 or so on a lithium ion jump pack to leave in your glove box.


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## homebrewed (Sep 21, 2022)

great white said:


> I’ll ask a simple question that hasn’t been asked yet: factory radio or aftermarket replacement?
> 
> aftermarket radios are notorious for parasitic drain.


We bought a used 98 Jetta that started randomly draining the battery.  Along with that, it would sometimes roll the power windows down by itself or unlock its doors and sometimes would quickly beep the horn a few times.  I recall one instance where we were passing a bicyclist and the car did that just as we went by -- like the poltergeist in the car was saying "Hi" to him.  I bet that was one baffled cyclist.

I found an anomalous current draw coming out of the battery but wasn't able to track down the source of the problem so we took the car to our mechanic, who did a more thorough job -- and traced the problem down to the car radio.  It WAS the factory radio.  Somewhere along the line somebody had stuffed a bunch of coins into the cassette slot, which found their way into the guts of the radio and started making random electrical connections.  As the coins bounced around the car's behavior would change in random and mysterious ways.  That was some ghost in the machine, eh?  Our mechanic had never encountered a problem like that one before.

The radio rattled like a piggy bank when we shook it!

Needless to say that radio got turned into e-waste.


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## Cadillac (Sep 21, 2022)

If the car has a key fob that can definately be the culprit if you are to close. I have a Cadillac xlr that in the service manual it states that the car is in search mode if it senses a fob within 25’. I had drained my battery twice because my kitchen where I hang my keys is like 18’ from the garage. Once I found that out I started leaving them in my bedroom. Been over ten yrs now no problems. 
 Disconnect the ground. When you go to put back on if it sparks your drawing power somewhere. With a meter you can go through your fuse box and see what pulling power with the key off.


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## WobblyHand (Sep 21, 2022)

Left it on trickle all night.  Seemed to think it was topped off.  Removed the charger.  Been letting it rest a bit to see what the battery voltage is.  Have not started the car today.  It's been a couple of hours, I will go check the voltage.

Found an inductive ammeter clamp that would work for my DVM, but I'm too cheap to buy it.  They want about $85, and it's not clear if it will measure down as far as I'd like.  The specs, or what they call specs leave much to interpretation and wishful thinking.  Don't want to be stuck with a piece of junk with limited utility.


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## WobblyHand (Sep 21, 2022)

12.58V at 4PM.  Battery had rested since Noon.  Had to go to the pharmacy.  Started without problem.  Restarted without problem.  I was glad of that!  Will trickle charge again tonight, and take the vehicle out for an hour spin tomorrow.  Time will tell if I averted a disaster.  

Honestly, I still think it is an unacknowledged Subaru bug.  

I have been trained by old fashioned cars - the kind that if you leave your lights on, any kind of light, you will have a dead battery.  Pretty careful to turn everything off that I can, because I remember being stranded.  Don't think it was anything that I did.  

I need to find my paperwork on the battery, or at least go look at the install date sticker.  I don't even know how old the battery is.  I'm guessing three or four years old.


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## great white (Sep 21, 2022)

WobblyHand said:


> 12.58V at 4PM.  Battery had rested since Noon.  Had to go to the pharmacy.  Started without problem.  Restarted without problem.  I was glad of that!  Will trickle charge again tonight, and take the vehicle out for an hour spin tomorrow.  Time will tell if I averted a disaster.
> 
> Honestly, I still think it is an unacknowledged Subaru bug.
> 
> ...


For reference, when a lead acid battery reaches approx 5 years old, its considered in it end of life cycle. It doesn’t just die (unless it experiences a catastrophic internal failure) but it looses capacity. Keep it in the car long enough and it just becomes too weak to keep up with the demands and it eventually dies outright.

Just something to keep in mind.


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## WobblyHand (Sep 21, 2022)

great white said:


> For reference, when a lead acid battery reaches approx 5 years old, its considered in it end of life cycle. It doesn’t just die (unless it experiences a catastrophic internal failure) but it looses capacity. Keep it in the car long enough and it just becomes too weak to keep up with the demands and it eventually dies outright.
> 
> Just something to keep in mind.


Not disagreeing at all.  However, I have had OEM car batteries last 10 years.  And some that last 4.  I am keeping my eye on this Lazarus battery. 

This is the second time I have rescued it.  Expecting to replace it, perhaps as soon as this winter, certainly within a year or two.  Really don't want to put much money into this car.  It just doesn't speak to me.  Yea, it is functional, but it doesn't make me glad to have it.  Previous cars made me a lot happier.  This one gets pushed around in the wind, a lot more than any sedan I have ever owned.  It can be scary.  It's somewhat boring and not fun to drive.  Hopefully, when the car crisis winds down, there will be something that's more my taste.


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## RandyWilson (Sep 21, 2022)

10 years from an OE battery in a modern vehicle with computer controlled charging is quite common. There is a reason for all the battery registration "nonsense", temp sensors, and such.


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## pdentrem (Sep 21, 2022)

My 2007 Cobalt’s battery was the factory issued one when I sold the car in April 2019. The Canadian Tire Eliminator battery I had in my 1969 Chevelle lasted only 18 months and it’s free replacement was the same. My 1988 Beretta had two batteries in it‘s 19 year life. The life spans of automotive batteries swing wildly but “usually“ OEM last the longest. Now motorcycle batteries, don’t get me started on the exceedingly short life the replacements one have!
Pierre


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## brino (Sep 22, 2022)

Years ago I made the transition to only buying interstate batteries as replacements, as I had a number of good experiences with those and bad experiences with other brands.

However, that no longer holds true..... the last interstate battery I bought will be the last one I ever buy. 
I once considered it paying a little more for quality, however now buying Interstate seems to be paying more for nothing!

Not to derail the thread, but I am still looking for a decent price, reliable source.

Thanks,
Brian


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## great white (Sep 22, 2022)

brino said:


> Years ago I made the transition to only buying interstate batteries as replacements, as I had a number of good experiences with those and bad experiences with other brands.
> 
> However, that no longer holds true..... the last interstate battery I bought will be the last one I ever buy.
> I once considered it paying a little more for quality, however now buying Interstate seems to be paying more for nothing!
> ...


I seem remember reading something a while ago that Interstate had changed suppliers to an “offshore” source and the quality went in the crapper shortly after…


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## WobblyHand (Sep 22, 2022)

great white said:


> I seem remember reading something a while ago that Interstate had changed suppliers to an “offshore” source and the quality went in the crapper shortly after…


Do you recall what year the supplier changed?  

In any case, I know I will be looking for new battery in a while.  Don't know how long this one will last.  Know any reputable quality battery makers these days?


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## great white (Sep 22, 2022)

WobblyHand said:


> Do you recall what year the supplier changed?
> 
> In any case, I know I will be looking for new battery in a while.  Don't know how long this one will last.  Know any reputable quality battery makers these days?


Nope, was a fair number of years ago iirc…

as to current products: nope, no recommendations. It’s quite literally a crap shoot.

Like most products these days, a name brand doesn’t mean you’re getting quality, just that you have a better chance if it. It’s all part of this race to the bottom that markets seem to demand these days….


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## wachuko (Sep 22, 2022)

great white said:


> I seem remember reading something a while ago that Interstate had changed suppliers to an “offshore” source and the quality went in the crapper shortly after…





brino said:


> Years ago I made the transition to only buying interstate batteries as replacements, as I had a number of good experiences with those and bad experiences with other brands.
> 
> However, that no longer holds true..... the last interstate battery I bought will be the last one I ever buy.
> I once considered it paying a little more for quality, however now buying Interstate seems to be paying more for nothing!
> ...


Same thing happened to me with Optima Red Top (and Yellow Top) batteries... that was the only brand I would buy for my cars or the boat... then the quality went to shi**

Was not aware that the same happened with Interstate... I switched to those after having issues with the Optima batteries... luckily, I have not purchase a car battery in over 8 years


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## pdentrem (Sep 22, 2022)

The last battery I bought for anything was an Odyssey for my late Honda Shadow. It was the only battery at the time that lasted as long as the OEM from Honda. The other replacements like Yuasa did not hold up. This is going back to around 2010.
Pierre





__





						ODYSSEY® Battery - Official Manufacturer's Site
					

Welcome to OdysseyBattery.com - the official manufacturer's website for the revolutionary ODYSSEY® battery. It has twice the power and triple the life of conventional lead acid batteries, and is ideal for car, truck and powersports vehicles, as well as marine and heavy duty applications.




					www.odysseybattery.com


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## great white (Sep 22, 2022)

pdentrem said:


> The last battery I bought for anything was an Odyssey for my late Honda Shadow. It was the only battery at the time that lasted as long as the OEM from Honda. The other replacements like Yuasa did not hold up. This is going back to around 2010.
> Pierre
> 
> 
> ...


The “modern“ choice for powersports batteries is AGM these days. They tolerate neglect much better than the old lead acid batteries. They also tolerate vibration much better than the old hanging lead plates in an acid bath. Vibration is a battery killer in street bikes and AGM just shrugs vibration off as a result of its internal design.

I’ve got 4 street bikes: 1985 Honda v45 Interceptor, 1982 Honda Cb650 Nighthawk, 1983 Yamaha Venture and a 1989 Yamaha FJ1200. 

Batteries are anywhere from 3 to 6 years old. All AGM and all still working. They also all came from CTC. The AGM construction and routine battery charging in the off months keeps them going and going.

I tried to find one for my 88 Corvette, but the price scared me off. 400 bucks for the Argo deep cycle AGM battery was enough of a wallet punch thank-you-very-much.


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## WobblyHand (Sep 22, 2022)

great white said:


> The “modern“ choice for powersports batteries is AGM these days. They tolerate neglect much better than the old lead acid batteries. They also tolerate vibration much better than the old hanging lead plates in an acid bath. Vibration is a battery killer in street bikes and AGM just shrugs vibration off as a result of its internal design.
> 
> I’ve got 4 street bikes: 1985 Honda v45 Interceptor, 1982 Honda Cb650 Nighthawk, 1983 Yamaha Venture and a 1989 Yamaha FJ1200.
> 
> ...


My miata had an AGM battery.  One of those batteries lasted for 14 years, parked outside, year round.  I like AGM's, but you do need to be careful when charging them.  

I suppose one could make a point for lithium batteries.  They do have size and weight going for them.  Quite pricey, however, and require different charging systems.


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## RJSakowski (Sep 22, 2022)

The battery in modern automotive electrical system is essentially always at full charge.  There is a very short duration  high current draw to start the vehicle and after starting, the alternator provides all the current needed for the vehicle's needs, including any auxiliary equipment as well as replacing the small amount of charge drawn during starting. The capacity of an alternator has no bearing on battery size.  Correct battery size is a function of starting needs.  Those of us living in northern climes need a battery that can turn an engine over in sub zero temperatures although this has become less important with smaller engine sizes and fuel injection.

Most modern alternators output a constant voltage of 14 volt which is a safe float voltage for a 12 volt lead acid battery.  The alternator in my 2016 Dodge is a 160 amp alternator, in my wife's 2013 Mazda, it is a 100 amp alternator.  Both are capable of meeting any conceivable demand I could place on them.  If a vehicle is draining the battery during operation, the alternator isn't operating properly.  If battery isn't holding a charge and the alternator is putting out 14 volts during operation, barring any unusual conditions like hard starting, a failed battery is suspect.

Batteries used in vehicles have capacities in the neighborhood of 50 to 100 amp-hrs.  In order for a battery to discharge in an overnight situation, the current draw would have to be several amps.  However, long periods of disuse is a different story.  After retiring, my wife seldom used her car, sometimes going for a month or more during the winter months.  She also used to leave her key fob in the car and we discovered its effect on battery drainage. During the height of the pandemic, I didn't use my vehicle for several months but didn't experience a flat battery.


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## great white (Sep 22, 2022)

WobblyHand said:


> My miata had an AGM battery.  One of those batteries lasted for 14 years, parked outside, year round.  I like AGM's, but you do need to be careful when charging them.
> 
> I suppose one could make a point for lithium batteries.  They do have size and weight going for them.  Quite pricey, however, and require different charging systems.


Nah, modern “smart” chargers handle agm batteries perfectly. They charge up to maximum and then switch to “float”, which keeps it fresh.
I use a Noco, but most any new smart charger with the option to select the type of  battery (ie: lead acid, agm, small, large, etc) will handle a modern agm. Pop it on, plug it in, make sure its set for the battery type and walk away. 

It’s routine to have 5-10 smart chargers going at any one time in my garage. They’re a big part of why my batteries last as long as they do.


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## wachuko (Sep 22, 2022)

great white said:


> Nah, modern “smart” chargers handle agm batteries perfectly. They charge up to maximum and then switch to “float”, which keeps it fresh.
> I use a Noco, but most any new smart charger with the option to select the type of  battery (ie: lead acid, agm, small, large, etc) will handle a modern agm. Pop it on, plug it in, make sure its set for the battery type and walk away.
> 
> It’s routine to have 5-10 smart chargers going at any one time in my garage. They’re a big part of why my batteries last as long as they do.


Depends on how depleted the battery is... I had to put two in parallel to be able to charge a dead AGM battery... to trick the charger into charging the dead one...


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## WobblyHand (Sep 22, 2022)

wachuko said:


> Depends on how depleted the battery is... I had to put two in parallel to be able to charge a dead AGM battery... to trick the charger into charging the dead one...


I have had to use a dumb charger to get the battery voltage up high enough that my smart charger would even try.  Think that was on one of my AGM batteries.  In that case, the smart charger wasn't smart enough...  It gave up too soon - before it even started.  But I was able to recover the battery for a few more years of use.  So it all depends.  

My battery was so depleted this time (flooded cell) that when I connected my dumb 2A charger, it pegged the meter and the charger made weird, I am dying noises, so I quickly disconnected it.  I then decided, what the heck, there's nothing to lose, lets connect the smart charger.  Apparently, the smart charger thought it was possible to proceed.


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## great white (Sep 22, 2022)

Double post


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## great white (Sep 22, 2022)

WobblyHand said:


> I have had to use a dumb charger to get the battery voltage up high enough that my smart charger would even try.  Think that was on one of my AGM batteries.  In that case, the smart charger wasn't smart enough...  It gave up too soon - before it even started.  But I was able to recover the battery for a few more years of use.  So it all depends.
> 
> My battery was so depleted this time (flooded cell) that when I connected my dumb 2A charger, it pegged the meter and the charger made weird, I am dying noises, so I quickly disconnected it.  I then decided, what the heck, there's nothing to lose, lets connect the smart charger.  Apparently, the smart charger thought it was possible to proceed.





wachuko said:


> Depends on how depleted the battery is... I had to put two in parallel to be able to charge a dead AGM battery... to trick the charger into charging the dead one...


Depends on the charger as much as anything else.

My Noco’s have a setting to recover a battery below the threshold where other chargers will call out a fault when you try and use them.

Battery chargers are an area where I always recommend to not “cheap out”. Take the pain now and buy a higher end one. In the long run, it will pay for itself.


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## WobblyHand (Sep 22, 2022)

@great white Have to agree with you on battery chargers.  Just have to fight the innate desire to cheap out.

@pdentrem Just checked the Odyssey battery out.  They seem to recommend a BCI# 25.  That's the little size isn't it?  The battery specs seem pretty good, though.  According to their configuration selector I get a part number of ODP-AGM25.  Going to say, wow, battery prices sure are high these days.  Their online store is listing the price at $318.26.  I'd gladly pay that for a car that I liked and wanted to keep around.  But, I am not going to pay that for this car.  When this battery dies, I will have to replace it with a lesser model.  I'd like to replace this car, but the pickings are sparse and expensive due to the chip shortage.  Hope that things improve to a more normal situation in the future.


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## pdentrem (Sep 22, 2022)

Quality is not cheap! Check out AC Delco maybe 3/4 of the price and they have never failed me.

As for the auto market. My contacts in the auto industry are not expecting normal until late ‘23 or spring ‘24. I have been seeing more haulers on the highway in the last 4 weeks. I don’t know if it is new year releases or catch up vehicles.

I have multiple trickle chargers for my car, bike, stand alone generator. Also have large manual and auto chargers. I prefer to use the trickles when possible. I hope you do use a battery or block heater for winter starts. Makes a huge difference on battery life.
Pierre


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## tq60 (Sep 22, 2022)

Batteries made by Ener-Sys will be good.

The RED ones are Virgin pure lead and they chat in their labeling.

On the battery plant side they had a 160 Amphr "package" that we determined would run the equipment a certain period before alarming, ran much longer and we ran out of day so returned to normal power.

Reverse engineered based on performance and determined it was a 190 amphr battery.

Price was also same as larger.

However the age degradation from 190 made the battery much longer life than the 160.

Sears diehard top of line is made by them but almost 2 times cost.

Other note is current cars to squeeze out every possible MPG control the charging by ECM.

Our F250 will not start charging for about a minute or so.

Work truck sometimes is just above 12 VDC and other times 14.

We have pursuit vehicles in assorted agencies, the chargers are labeled as AGM and should be starved electrolyte meaning no liquid.

The chargers all run hot, 14 VDC plus which AGM do not like.

Top blew off one the other day, had liquid inside.

Last battery we bought was a group 27 for the bobcat.

Current common practice is no longer pro-rating.

Back in the day the better batteries we maybe 7 year with first 2 or 3 years direct exchange with pro-rating after that.

Now you pay the 7 year price but only get 3 year warranty.

We called a local family run battery place, older than dirt, they provided the batteries for the trucks that brought in the dirt.

2 year "blem" battery, 65 bucks out the door, Sam's wanted maybe 150 or so.


Sent from my SM-G781V using Tapatalk


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## great white (Sep 22, 2022)

pdentrem said:


> .I hope you do use a battery or block heater for winter starts. Makes a huge difference on battery life.
> Pierre


my truck and the wife’s minivan both have blankets and block heaters.

Never use them though. One if the “perks“ of having a heated garage. Never drops below 10c…..


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## Cadillac (Sep 23, 2022)

Diehard batteries were top of the list last I had checked. Crown battery is also a good brand. Gotta watch out if buying interstate batteries through a dealer. I’ve run into they have two battery prices reconditioned and new.


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## WobblyHand (Sep 23, 2022)

Cadillac said:


> Diehard batteries were top of the list last I had checked. Crown battery is also a good brand. Gotta watch out if buying interstate batteries through a dealer. I’ve run into they have two battery prices reconditioned and new.


What do you mean by dealer?  There's an Interstate owned store nearby me.  They could have sold me a battery last year, but instead told me, the battery was still was good.  (They tested it.)  Not many places that will do that these days...  

In full disclosure, that battery I brought to them was an Interstate that I had bought from their store some years earlier.  The battery has been deep discharged twice now.  As far as I can tell, I did nothing to cause the discharge.  There were no keys nearby, nothing was left ajar, no lights on, etc.  Still think there's a bug in the Subaru ECU shutdown code...  Only way to find it would be to put on a permanent current monitor, but that's more money that I don't want to sink into this vehicle.  If it was my sports car, yeah, I'd find that darn drain.  This car, nope.  Not in love with this one.


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