# Cen-Tech battery charger -Harbor Freight



## Janderso (Jul 22, 2020)

I had a long rough day at work. My wife and I are taking the RV out for a four day excursion to the mountains around Mt Shasta, Ca
I get home, change, run over to the storage lot to pick up the trailer. (I had two old Sears that worked great for decades, lost in the fire)
Can’t load the trailer, I left the battery switch connected, both dead.
No problem I says to myself. I’ll head over to Harbor Freight and pick up a charger.
$54.99 for a 2-10-50 amp charger.
I have one of the batteries from the trailer, set it on the bench and connect the Cen-Tech charger.
Nothing. No power, no red light, nothing.
What a PITA.


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## westerner (Jul 22, 2020)

New chargers will not engage if they do not detect a battery. Meaning, if the battery is so dead as to appear invisible (electrically) to the charger, it will not 'turn on'


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## westerner (Jul 22, 2020)

I have found that in the case above, ya gotta put another battery in parallel with the one you desire to charge, to prove to the charger there is actually a battery hooked up. Once your 'dead' battery comes up enough, you can remove the 'proxy', and get on with life.....
My old charger from the 70's does not care. It assumes you know what you are doing. Bloody nannies these days, anyway.....


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## Janderso (Jul 22, 2020)

westerner said:


> New chargers will not engage if they do not detect a battery. Meaning, if the battery is so dead as to appear invisible (electrically) to the charger, it will not 'turn on'


Really?
Ah, ok, I’ll take it and my battery to work and check it out.


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## westerner (Jul 22, 2020)

Oh, yes. There is internal circuitry that will prevent the charge circuit from switching on if a load (battery) is not detected. I have seen it on every charger I have been around that was made in the last decade or so, or longer.

I assume the nannies are keeping us from throwing errant sparks around the shop.


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## Ed ke6bnl (Jul 22, 2020)

I have 2 old school 10,50,200 amp chargers with timers on them. I even have an extra progressive dynamic with the gennie for boost mode.


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## Janderso (Jul 22, 2020)

My old Sears charger didn’t care.


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## mmcmdl (Jul 22, 2020)

OT Jeff , but I just watched a show on the Weather Channel about the Paradise fire . I'm glad you are still with us !  That was a major tragedy to say the least .


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## Janderso (Jul 22, 2020)

It was an experience I never want to go through again.
Pitch black, explosions, fire.


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## mmcmdl (Jul 22, 2020)

Janderso said:


> It was an experience I never want to go through again.
> Pitch black, explosions, fire.


I would certainly say not .


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## mmcmdl (Jul 22, 2020)

I blew my old time charger up 2 years back and ended up with a Schumaker (sp) jump box from TSC . This has jumped everything so far , other than me . I think my internal battery is shot .


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## arvidj (Jul 22, 2020)

I've always assumed the "does not know a battery is there" was one end of the spectrum of smarts my chargers have with the other end of the spectrum being "turn off or at least way down when charged so you don't cook the battery dry".

Of course a product designer who actually used his device might have added a 'push this button to get a completely dead battery off the ground' but they probably never actually use their pruducts in real life situations. The test lab batteries alway have enough of a charge to get things started so real situations are never tested.

Sorry, got a little carried away with the sarcasm


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## projectnut (Jul 23, 2020)

We had a similar problem with the coach batteries in our motorhome a couple years ago.  In our case we were on the road in Alaska when the onboard charger decided it was time to give it up.  The batteries probably weren't quite as bad as the ones in your travel trailer, but they were far to weak to even turn on the LED lights.

I went online to the NAPA Auto Parts website and found this battery charger:



			https://www.napaonline.com/en/p/SORPL2320C?partTypeName=Battery+Charger&keywordInput=battery+charger
		


It isn't the cheapest in the world, but it's in a different league than the Harbor Freight ones I have at home.  It's now become my go to charger for everything from a garden tractor to the motorhome.  I've even used it on my end loader that hadn't moved in nearly a year.  The battery was so dead it wouldn't light up a 1157 bulb, but the charger detected it and was able to charge it.

I do have an older Schumacher commercial 2/40/200 charger/starter in the garage.  It's been a good machine, but even it doesn't compare to the new Pro Logix one for charging a dead or nearly dead battery.  It's the old style bulk charger with no capacity for multistage charging.  I keep telling myself it's time to dump the old Harbor Freight models that barely worked when they were new.


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## RJSakowski (Jul 23, 2020)

I left a circuit on in my boat last summer and when I discovered it, the deep cycle battery was dead flat.  I managed to put somewhat of a charge on it but it never recovered.  Over the winter, it went flat again, presumably die to an internal short, and froze.  Dead meat!


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## markba633csi (Jul 23, 2020)

Some cordless tool chargers won't charge a totally flat battery either,  what a goofy feature
-Mark


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## Janderso (Jul 23, 2020)

I took the battery to work this morning. I hooked it up to our smart charger. It's a Midtronics product. they run about $1,300.
Watching it go through the diagnostics and watching the display was interesting.
It started out at 1.7 volts DC. That was after a 12 hour charge with my 2 amp charger.
It's so dead it needs a jolt but it's a deep cycle type marine battery.
This charger started a 2 hour charge. The initial ramp was 12 volts at 5 amps. As you watch the screen the amps came up by tenths every minute or so. It stopped at 59.1 amps and 15.6 volts. This was after about 35 minutes. The battery was very warm to the touch. I let this go a bit more then moved it to a 12v slow charger.
I now have 12.6 volts after it sits for half an hour.
I think it will be OK.
I don't think the other battery will charge driving down the highway. I might just leave it home or disconnected until I can get a proper charge on it.
I'm curious what my new Cen-Tech does when I test it tonight when I get home?
At least I will see if it works.


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## Janderso (Jul 23, 2020)

The charger worked as designed.
You guys are right. If the battery is really dead there will be no output, no red light, nothing.
I connected the fresh charge with the stone dead battery. The charger came alive.
I put a ten amp charge for an hour then separated the two.
Now I have 12 volts on the second battery.
I’ll charge it by itself for a couple hours now.
Done!
Revived.
I need to make sure to disconnect the battery circuit when I store it.


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## DavidR8 (Jul 23, 2020)

Batteries are a deep topic. 
When I owned a sailboat I did extensive research into DC charging systems. 
A fully charged 12v battery will read about 12.9v and about 11.9v when fully discharged. 

Anything less than approximately 12.4v leads to sulfatation which is the death knell for lead-acid batteries. If a lead-acid battery is left in a discharged state for long periods they cannot be revived to have anything close to original amp-hour capacity. 

I recommend getting a solar trickle charger to maintain charge when the RV is not in regular use. Put it in a south facing window and connect it to the batteries as directly as possible. 


Sent from my iPhone using Tapatalk


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## Janderso (Jul 24, 2020)

Good idea David. I have hesitated because I thought it would get stolen. I never thought of putting it inside.
Wont the tinted windows cut the UV’s?


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## Flyinfool (Jul 24, 2020)

The windows will cut the output a bit, but it will still work.
I have had a small solar panel on my RV and the battery is now 15 years old and going strong.
I put my panel up on the roof, Not attached just toss it up there right above the entry door. Just inside the door is a 12V outlet that I plug it in to.
Just remember to take the panel off the roof BEFORE you start driving, 

Be careful trying to charge a really dead battery while driving. As you noticed it got hot and was pulling in 56 amps, That is a lot of load for a long time on the tow vehicle alternator and has a danger from an overheated battery. I have seen alternators have a short service life when doing a lot of heavy charging.


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## Janderso (Jul 24, 2020)

Flyinfool,
I think you found the trick.
I'll look into a device.


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## Janderso (Jul 27, 2020)

We are back from camping in the Shasta Trinity National Forest.
The batteries were fully charged on the drive up showing Full.
We went four days without an issue.
I powered up the Honda generator once so my wife could charge the I-Pads we use to read.

When I drop the trailer off tonight at the storage lot I will be sure to separate the internal draw from the batteries.


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## Superburban (Jul 27, 2020)

Flyinfool said:


> Be careful trying to charge a really dead battery while driving. As you noticed it got hot and was pulling in 56 amps, That is a lot of load for a long time on the tow vehicle alternator and has a danger from an overheated battery. I have seen alternators have a short service life when doing a lot of heavy charging.


I learned that the hard way while traveling.I had a suburban with the GM 6.2 diesel.  The morning we were to leave, both batteries were dead. I jump started it, and then about 7 hours later, the alt was dead.


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