# 72V charger - help a NOOB out with basics please



## crazybry79 (Jun 15, 2010)

OK, I am running an old forklift system (EV100) in a geo metro. At the moment, I have (4) 12V deepcycle (golf cart) wet batteries powering my set up. To charge, I have been disconnecting the batteries, and putting (1) 12V charger on each battery.

Now, in the reeeealy near future, I will be putting another (2) batteies on the pack, making 72V. I have purchased a 72V, 12A charger that will be mounted in the car, and connected permanently. 

My first question is, in my current set up, when I charge my batteries, I have been simply removing one of the cables that goes from a negative to a positive (breaking the circuit) before I charge. Could I leave the cable on to charge? Would it still charge each battery (assuming I have (1) 12V charger on each battery)? Or do I need to break the circuit like I have been doing?

My second question is, did I use the correct thinking here.... I wanted to charge my 72V pack. Cost limited me to (6) 12V chargers, or (1)72V charger. The charger I bought is 72V, 12A. Is that going to be enoughh amps to charge a pack in a reasonable timeframe? (say overnight /8 hours). 

How does that work, comparing say a 10A 12V charger set up (say (6) 10A 12V chargers) vs a 72V set up? Wouldnt my 72V charger need to be 60A to do the work of the (6) 12V chargers?

heres the charger I got...


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## vpoppv (Jul 27, 2009)

crazybry79 said:


> OK, I am running an old forklift system (EV100) in a geo metro. At the moment, I have (4) 12V deepcycle (golf cart) wet batteries powering my set up. To charge, I have been disconnecting the batteries, and putting (1) 12V charger on each battery.
> 
> Now, in the reeeealy near future, I will be putting another (2) batteies on the pack, making 72V. I have purchased a 72V, 12A charger that will be mounted in the car, and connected permanently.
> 
> ...


First off, all six of my chargers are all permanently connected and I just plug them in when I need to- no need to break any circuits. Each charger only "sees" the battery it is connected to. Has worked flawlessly for almost 2 years now. For the next part, a 72v, 10 amp charger is like 6 12v chargers running at 10 amps because they put out the same power. 72v x 10 amps = 720 Watts which is the same as 6x10 amps x 12v = 720 Watts 

Also, with regard to the "hot" cables in your setup, although I am using 2 AWG, when I first started testing it, the old 6 AWG I used was cold to the touch because I was running 72v. With only 24v, you are running much higher currents and the 6 AWG isn't sufficient. When you get to higher voltages, they won't get hot. Congratulations on making another Geo electric!! I still love mine, but can't survive it in this triple digit weather. Hope this helps!


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## crazybry79 (Jun 15, 2010)

Helps a bunch!!

I certainly thought that when I raised the voltage, the amperage would drop. My cables got warm before - I could hold them, uncomfortably. Now, at 48V, I have a 2 AWG running between 2 batteriews in my pack, and it got untouchable hot. Now one of the nuts holding that cable on was loose/corroded, but the remaining cables that were 2 AWG got pretty darn warm too.

Now, I can control the amperage the controller puts out, and also the amperage that the 1A bypass is allowed. Should I be cutting my amperage back?? Would one loose nut / poor connection cause the whole system to warm up?? (I had a lock nut on the battery post on THAT loose connection....and it melted the plastic out of the lock nut...


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## vpoppv (Jul 27, 2009)

crazybry79 said:


> Helps a bunch!!
> 
> I certainly thought that when I raised the voltage, the amperage would drop. My cables got warm before - I could hold them, uncomfortably. Now, at 48V, I have a 2 AWG running between 2 batteriews in my pack, and it got untouchable hot. Now one of the nuts holding that cable on was loose/corroded, but the remaining cables that were 2 AWG got pretty darn warm too.
> 
> Now, I can control the amperage the controller puts out, and also the amperage that the 1A bypass is allowed. Should I be cutting my amperage back?? Would one loose nut / poor connection cause the whole system to warm up?? (I had a lock nut on the battery post on THAT loose connection....and it melted the plastic out of the lock nut...


Well one loose nut will cause untouchably hot (ask me how I know  ), but probaly not in the whole system. Do you know how many amps you are running? I'd be a little worried if 2 AWG is getting hot. But then, I never even tried running under 60v, so what do I know?? Maybe someone a little more knowledgeable can tackle this one.....


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## Coley (Jul 26, 2007)

I run a 72volt, 20amp charger on my Yugo.

I use No.2 cable and nothing gets hot.

The charger is connected permanently to the pack.

I turn off the main swith to the controller and the ignition switch that goes to my relays, before I turn on the charger. Approx 3-4 hrs. to charge my Gels.

It has worked well for me.

When my car was 48volt I hooked everything up the same way.


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## crazybry79 (Jun 15, 2010)

As far aamps.......I'm not sure. I will have to check. I belive the controler / 1a is set up for 1250A. Id have have to doublecheck. 

Now whem I was running 24V, if the controler was set for say 300A (fictional number), and now I bumped it up to 48v, and never changed the amp setting, could that be a problem? Should I cut my amps down if that if the case?

24v @ 300 amps could be thr same performance as 48v @ 150A, right?


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