# Golf Cart Charger



## GA Gyro (May 10, 2015)

I am not sure if this is the correct forum... however my question is electrical...

At the airport where the gyro's are... we have an old golf cart we use to ride around the airfield... it is quite popular, given our hanger is one of the farther from the office and runway.

A week or so ago, the charger quit working... so I brought it home over the weekend.  
After taking it apart, I find a BIG transformer, a fuse of sorts, an ammeter, a relay, and a half wave rectifier.  

It appears the rectifier opens when a load is put on it... so I am thinking to find a new way to turn AC to DC.  

The golf cart has 6 x 8V batteries, for a total of 48 volts.  I might mention that one of them measures 4+ volts, two measure 6.25 and 6.33 volts, the other 3 measure 8+ volts... for a total of 41-42 volts.  All the 6 batteries have been filled with fresh distilled water. 

There is a relay in the charger that is supposed to verify connection to batteries, before starting the charger (controls the 120V AC circuit to the transformer)... I am wondering if the relay is failing... I do not have a variable DC power supply to test it.  

Do any of you have experience with these chargers... any and all thoughts, suggestions, comments, pokes, etc... are greatly appreciated.  

And one more question:  Where would I find a half wave rectifier (two inputs, one output), that can handle 20+ amps @ 48V... preferably 30A would probably be better.  THX in advance for any sources!


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## Boswell (May 10, 2015)

A few things you need to look at. First a Half-wave rectifier is commonly known as a diode and would have 1  input and 1 output . A full wave rectifier is a bridge of 4 diodes with two inputs and two outputs. While there may be something I am not aware of any common AC/DC conversion things that would have 2 inputs and 1 output. Could one of the outputs be disguised as a case/chassis ground?  What specifically do you mean by "The rectifier opens when  a load is put on it"?  What voltage do you get from the rectifier when there is NO load ?  Golf carts are extreemly common, I would expect that every part possible is available online both new and used.


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## GA Gyro (May 10, 2015)

Boswell said:


> A few things you need to look at. First a Half-wave rectifier is commonly known as a diode and would have 1  input and 1 output . A full wave rectifier is a bridge of 4 diodes with two inputs and two outputs. While there may be something I am not aware of any common AC/DC conversion things that would have 2 inputs and 1 output. Could one of the outputs be disguised as a case/chassis ground?  What specifically do you mean by "The rectifier opens when  a load is put on it"?  What voltage do you get from the rectifier when there is NO load ?  Golf carts are extreemly common, I would expect that every part possible is available online both new and used.



To answer your question... which I kinda anticipated... after I posted...
The transformer has two secondaries, in parallel... so the two inputs and one output is two windings.  Note the secondary is NOT a center-tap transformer, it actually has two sets of secondary windings, as well as one primary windings.  
(As you can tell, I have an electrical background als0...  ).

The diode bank is a buss bar with a couple of lumps of something, about 3/8 in dia and about the same length, held in place with copper spring bars.  The buss is the common, the two CU/spring bars are the terminals.... the lumps must be the diodes.  

I was hoping someone that was familiar with golf cart chargers, and knew of a source for modern diodes, would come along with a link... 

THX for your input, all input is welcome!


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## RJSakowski (May 10, 2015)

A diode array with two inputs and one output is called a half bridge.  They are commonly used with center tapped transformers to provide full wave rectification.  A dual output transformer with the windings in series and in phase functions as a center tapped winding.

Modern diode of ample current and voltage ratings abound. From your description, it looks like you are charging a 48 volt battery bank.  You don't say what the charge current is but I would guess somewhere in the neighborhood of 15 to 20 amps.  The reverse voltage rating on the diode should probably be 200 volts.  If you can't find a half bridge, you can use one half of a full bridge or you can use two individual diodes.  You will want to provide adequate heat sinking.

If you check DigiKey, Mouser, or Newark, you should be able to find diodes to meet your requirements.  all of them have on-line selection apps to narrow your search. About half bridges; they come in two flavors, common anode and common cathode.  you need to pick the correct one.  Many of the half bridges have no markings to distinguish  one from the other, other than their part number.


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## GA Gyro (May 10, 2015)

RJSakowski said:


> A diode array with two inputs and one output is called a half bridge.  They are commonly used with center tapped transformers to provide full wave rectification.  A dual output transformer with the windings in series and in phase functions as a center tapped winding.
> 
> Modern diode of ample current and voltage ratings abound. From your description, it looks like you are charging a 48 volt battery bank.  You don't say what the charge current is but I would guess somewhere in the neighborhood of 15 to 20 amps.  The reverse voltage rating on the diode should probably be 200 volts.  If you can't find a half bridge, you can use one half of a full bridge or you can use two individual diodes.  You will want to provide adequate heat sinking.
> 
> If you check DigiKey, Mouser, or Newark, you should be able to find diodes to meet your requirements.  all of them have on-line selection apps to narrow your search. About half bridges; they come in two flavors, common anode and common cathode.  you need to pick the correct one.  Many of the half bridges have no markings to distinguish  one from the other, other than their part number.



Thank you!

Yes, the charger does charge the entire 48 volt battery array at once...
The input of the charger is 120V and 10A...
The output is 48V and 18A.

Thx for the reverse voltage rating (200V)... that is one thing I did not consider.
I was hoping to find the type of diode that looks like a top-hat, with a locknut... and mount two of them on a finned heat-sink.  
Good suggestion to call Digi-key... will do so in the morning.

How would I know whether to use common anode or common cathode?

THX

John/GA


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## RJSakowski (May 10, 2015)

Here is a power rectifier, 200 piv, 30 amp half bridge common anode: http://www.digikey.com/product-detail/en/APT30D20BCAG/APT30D20BCAG-ND/1494472
And her is an individual rectifier 200 piv, 30 amp: http://www.digikey.com/product-detail/en/APT30D20BG/APT30D20BG-ND/1494474


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## JimDawson (May 10, 2015)

That sounds like two half-wave rectifiers in parallel, don't think I've seen that one before.

This is what I would get for replacement diodes  http://www.digikey.com/product-detail/en/VS-70HF40/70HF40-ND/82882


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## GA Gyro (May 10, 2015)

THX...

I was thinking about this... I need to go out to the hanger and look at the wiring of the batteries and the charger outlet/plug (between the charger and cart)... to determine the direction of current needed to charge them.  This should answer the anode/cathode question...
Sometimes I think I have 'part-seimers'... I have to think about something for a few minutes... and the answer becomes obvious...


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## GA Gyro (May 10, 2015)

JimDawson said:


> That sounds like two half-wave rectifiers in parallel, don't think I've seen that one before.
> 
> This is what I would get for replacement diodes  http://www.digikey.com/product-detail/en/VS-70HF40/70HF40-ND/82882



Ahhh, yes!

That was what I had envisioned... two of those, mounted on a finned heat sink... with the heat sink electrically isolated from the case.  
THX Jim!


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## RJSakowski (May 10, 2015)

GA Gyro said:


> Thank you!
> 
> Yes, the charger does charge the entire 48 volt battery array at once...
> The input of the charger is 120V and 10A...
> ...


If the common terminal of the half bridge goes to the positive side of the battery array , it is common anode.  This is most likely what you would have as the ct of the transformer windings usually is grounded.
In the 30 amp region, it is not likely that you will find the top hat type rectifier.  They cost much more to make in that configuration.  I have seen some in the 100- 600amp region.  They come with braided wire pigtails.  If you really want that type of package, you can specify stud mount as one of the search parameters in the selection app.


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## Tony Wells (May 11, 2015)

Check with your LWS. If they do repairs, they will have diodes of sufficient capacity if you're in a hurry.


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## GA Gyro (May 11, 2015)

Tony Wells said:


> Check with your LWS. If they do repairs, they will have diodes of sufficient capacity if you're in a hurry.



THX Tony!

I will need to go to the hanger and look at the wiring between the charger and cart... to determine polarity... and thus the type of diode (anode or cathode).  The hanger is 71 miles away, and I will be out/town this weekend... probably get there Sat the 23rd.  

Soooo... time is not an issue.  

Most of us at the hanger will be in NC this weekend... at a gyro-copter gathering.  It is at Anson Cty airport if anyone is in the are... come on out Saturday.


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## Bill C. (May 11, 2015)

Do you see signs of or smell burning? I hate open circuits when there are no signs of burnt diodes or  resistors.  Radio Shack used to carry some of the heavy duty components.  

If you have trouble finding replacement parts check with a industrial supply house that handles control panels.

Hope you get it up and running soon.


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## GA Gyro (May 11, 2015)

Bill C. said:


> Do you see signs of or smell burning? I hate open circuits when there are no signs of burnt diodes or  resistors.  Radio Shack used to carry some of the heavy duty components.
> 
> If you have trouble finding replacement parts check with a industrial supply house that handles control panels.
> 
> Hope you get it up and running soon.



No, no signs or smells of letting the magic smoke out... that would make it easy to figure out...


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## hgk (May 14, 2015)

FWIW in case your charger is similar, a you tube link for golf cart charger repair:


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## WisJim (May 14, 2015)

I would also point out that you have a battery problem, as all 8 volt batteries should measure well over 8 volts when charged.


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## GA Gyro (May 14, 2015)

Thank you... that video confirmed the diodes are bad (the diodes DID cause the meter to beep in the one I am working on).

Interesting board... Mine only has a hard-wired relay.  I may get the board and adapt it into the charger... would probably be a good thing.

THX again!


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## GA Gyro (May 14, 2015)

WisJim said:


> I would also point out that you have a battery problem, as all 8 volt batteries should measure well over 8 volts when charged.



Hmmm... I think that is obvious... since the batteries were measured independently.

Since this golf cart was a donation, and it is used for a few runs to the office once a weekend (probably max of 1 to 1.25 miles per weekend)... we probably are gonna let the batteries go for a while... until the cart slows down. 

I have been wondering one thing though... is there a point where the relay in the charger will not allow charging, due to low battery voltage?  If so, on a 48 volt system, what is that voltage?  THX


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## Round in circles (May 14, 2015)

Each lead acid cell should be 2.2 volts fully charged  when disconnected and at rest ..... say a few min after begin individually charged.
So each battery being 4cells x 2.2 volts =8.8volts 
Total package 6 sets of battery = 52.8 volt when fully charged.  Your charger must be capable of pushing this voltage plus four or five more volts to put a charge into the whole battery package .

 Do make sure your batteries are individually charged & tested off the buggy before you hook up the vehicle charger to a fully connected battery pack or you're likely to end up with yet another set of blown diodes.

 Don't just change one diode either .. as all the others will tend to be of the same age and have been subjected to the same stresses, which therefore makes them unreliable components  in the long term .


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## randyc (May 14, 2015)

JimDawson said:


> That sounds like two half-wave rectifiers in parallel, don't think I've seen that one before...



Me either.  The disadvantage of such an arrangement is the possibility of one diode "hogging" most of the current and overheating resulting in "thermal runaway".  A small series resistance in each diode would minimize that effect but would add to the voltage drop, thermal and mounting issues and cost.  A really, really excellent publication that addresses all of these problems is:

"Rectifier Applications Handbook", Motorola HB214


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## GA Gyro (Sep 9, 2015)

Well... My apologies... never did follow up...

Repaired the charger by replacing the diodes and building a custom heat sink (made the heat sink from a piece of 1.5 x 1.5 .125 wall AL sq tubing 5" long... a suggestion from the guy at DigiKey when I ordered the diodes).  

Charger works fine now... however the batteries went south.
We decided to replace the 6x8V batteries, with 4x12V batteries... LOTS less $$$.  

Golf cart works fine now... the guys at the hanger appreciate having it...
And I appreciate the help you guys offered to get it running again!

Now for a brake job this fall... the brakes seem to 'snatch'... like work out shoes.


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## GA Gyro (Sep 9, 2016)

Re-visiting this thread...

Seems the batteries in the golf cart have gone south again...
At this point it does appear the charger still works.
Honestly, I have not been to the airport much this summer... my gyro needs some major work, and it is has been a banner year for AC repair and replacement.

Anyhow...
We 'economized' and used 4 x 12V automotive batteries last year... it seemed to work... for a while anyway.
Now a couple of them are low voltage and the charger will not stay engaged. 
When the charger is plugged into the battery array... the internal relay clicks, the amp meter on the charger comes up to 15-16 Amps... then after a few seconds the amp meter goes to zero.  Disconnect the charger and wait a few seconds... same thing.
Am thinking, since the total of independent 'at rest' battery voltage is below 40 volts... we need to replace the batteries again... or at least the low voltage ones (2)... they were used auto batteries when they were put in last summer.

Anyone have any thoughts on using automotive batteries on a golf cart? 
The load is probably something like 1/2  of a 9 hole round of golf, over a 5-6 hour day... then on the charger until next weekend. 
During the summer, maybe this same usage 2x per week (few days between). 

Any thoughts, ideas, inspirations, shop wisdom, etc... is appreciated!

GA


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## JimDawson (Sep 9, 2016)

Maybe deep cycle batteries would be better.  It is possible that the batteries are being ''cooked'' by over charging.  Maybe put a timer on the charger.


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## Superburban (Sep 9, 2016)

This battery charger has been worth its cost. My golf cart charger was always showing signs of over charging (bubbling batteries, and leaking out the vents) the batteries. Every spring I charge each battery separately to make sure they are all fully charged. It goes through a charge and the test cycle until the battery will not accept any more charging.

http://www.samsclub.com/sams/stanley-golf-cart-vehicle-6v-48v-battery-charger/prod1841149.ip


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## David S (Sep 9, 2016)

There is a difference between automotive SLI batteries and deep discharge lead acid batteries.

Automotive batteries are designed for quick high current delivery for starting and have many thin plates.  Deep discharge batteries have thicker positive plates and and are less susceptible to grid corrosion due to continuous charge and are designed for deep discharge like stationary or traction vehicle applications.

David


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## TOOLMASTER (Sep 9, 2016)

do you rotate your batteries?


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## dieselshadow (Sep 9, 2016)

TOOLMASTER said:


> do you rotate your batteries?



Can you elaborate on what you mean? If he has six batteries, it wouldn't matter how they are wired in series. Battery "A" doesn't care if it's the 3rd battery, 1st or last. 6 batteries in series is still six batteries in series. Now if he needs 6 batteries and he has 8 in the shop, do you mean he needs to pull two out of use and install the spare two? Kinda like you rotate a full size spare tire?


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## kd4gij (Sep 9, 2016)

There is a huge difference in golf cart batters and automotive battery's.  Get 8v golf cart battery's and save in the long run.


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## GA Gyro (Sep 10, 2016)

THX for all the input...

The idea of asking the question... was to keep costs down...
Around here... a deep cycle battery is min $100+ each...
We got a year out of 4 automotive batteries... total cost $140...
Go figure... 

Looking for subtle ideas to keep from spending the big bucks for a set of deep cycle batteries.
If we do end up going that route... 4 x 12V for a cost in the $400-450 range makes more sense than
6 x 8V with a cost in the $600-700 range. 

Golf cart gets about the equivalent of less than one round of 9 holes, once a week. 
During the summer... maybe 2x/week.

The timer on the charger, or a better charger, seems a good idea.

Any and all ideas welcome!

THX

GA


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## David S (Sep 10, 2016)

GA I think first you should determine the amount of run time you need for your cart.  Popular 6v golf cart batteries have about 200 ahrs @ 25 amps and weigh around 70 lb.  this is just one example.
A reasonable deep discharge group 27 12v marine battery has about 63 ahrs @ 25 amps.
If you don't require the run time of the higher amp hour batteries then 4 marine batteries should work.
In my motor home I use 2 series 12 golf cart batteries for the house battery.
If you need capacity in the 200 ahr range then 6 or 8v packages are more manageable to carry and handle, however the down side is lots more interconnecting cables.

I believe Stanley makes a reasonably priced smart golf cart charger if yours isn't working correctly.  I have not tried it, but was reviewing for my son's cart.

David


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## Keith Foor (Sep 18, 2016)

Looks like fun stuff.
Now, using car batteries is gonna continue to be a problem.  Not only are you putting loads on them they are not designed for, but you are actually charging them wrong.  Lead acid batteries are 2.2 volts per cell.  They are charged at 2.4 volts per cell and their charge current varies depending on the design.  Car batteries are actually designed to be hard charged at high current for a short time.  Similar to the way they are discharged.  with what you are doing, you are putting a varying load on them for longer intervals and discharging them beyond their design.  A car battery should never be discharged below 2.0 volts per cell.  When you do this, you loose up to 20% of the capacity of the battery.  The 20% part happens when you get it down below 1.85 volts i believe, but you can look it up. Now, this applies to deep cycle batteries as well.  Hence the reason that they run 6 volt batteries.  Because each cell has it's own capacity it the cells in a 6 volt (3 cells instead of 6 cells) each cell has greater individual capacity.  This means it takes longer at the same current draw to drop the cell voltage down to a discharged state.   Now of course as mentioned above, over charging is as bad as under charging.  What overcharging does is creates sulfides in the battery.  The sulfides which are mildly conductive leach to the bottom of the battery and short out the individual cells.  This is one way that you can get a battery to suddenly have 10 or 11 volts coming out of it and no way to get it to charge beyond that voltage.  And once it occurs, the other cells in the battery now have additional charge voltage across them because one cell is shorted out and the rest of the battery quickly sulfides up and dies.  

So as far as the car battery being cheaper.  Not really.  If you have to replace the batteries every 6 months and it costs 150 to do it.  And the proper batteries cost $500 but you only need to replace them every 5 years, it's not really cheaper.


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