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issue with battery hook up in series (24V circuit)

issue with battery hook up in series (24V circuit)

issue with battery hook up in series (24V circuit)

Hi everyone,

We are having an issue with two 12V battery hook up in series. The complete systeme is a 24V including the alternator and is from an excavator. We have a GPS that draw 0.01amp when the machine is stopped. We have changed two battery on the same side in the past 6 months. Each time the battery is situated on the same side. On the ground side of the hook up. The battery are the exact same one CCA and all. Can someone explain me what can cause that battery to go dead and not the other one. By the way there is nothing hook up on the battery.

Thank you  

RE: issue with battery hook up in series (24V circuit)

"By the way there is nothing hook up on the battery"

So you say, but have you proven it?

How do you know both batteries are being charged at all?  

And what is the failure mode?


FAQ731-376: Eng-Tips.com Forum Policies

RE: issue with battery hook up in series (24V circuit)

There are only two possibilities. Your charging system is only hooked up to one of the batteries OR you have a load hooked up, (even a small one), to only the battery that is dying.

Remember that even a small drain that runs 24hrs a day will relentlessly drain a big battery.

I fully expect that your GPS draws a little more than 10 milliamps and is hooked to only one of the batteries as it is probably only 12V.

My recommendation would be to find which battery it is hooked to and add a small invisible roof mounted solar panel that can provide 5 times what the GPS draws.  Make sure the solar charger has an electronic charge controller with it. This solar panel would be quite small, perhaps the size of a sheet of paper.

Check West Marine for an example.


Keith Cress
kcress - http://www.flaminsystems.com

RE: issue with battery hook up in series (24V circuit)

Thanks for the reply,

The GPS is a 24V from factory. The battery that is getting bad after time has the ground side hook  up with a cable from the terminal to the frame of the machine. The positive side of the same battery is hook up on the negative side of the second battery (hook in serie). There is only the cable between these two battery so nothing is hook up to draw from this battery. Now the second battery positive side is hook up to the power supply of the unit. The alternator is a 24V and the output is directed to the positive side of the battery and alternator is grounded on to the frame. As I already mentionned with the key turn off the amperage being draw is only 0.01amp. Now I would imagine that both battery should go evenly down both long term that is not what is really happening.

Again thank you for the reply

RE: issue with battery hook up in series (24V circuit)

You might want to check that the cable between the batteries doesn't have a sneak path to ground.  

You still have explicitly said what the failure mode is, but it sounds like it's not holding charge?  

Over what period of time?

Have you verified the voltages on the batteries when they supposed to be fully charged?


FAQ731-376: Eng-Tips.com Forum Policies

RE: issue with battery hook up in series (24V circuit)

OK.. Well then, we must delve deeper.

Are the batteries the same brand and size?

Where are you getting them?

Are they non maintenance or do they have caps you can pull off?

The last battery I purchased from Kragens(Auto Zone) had a bad cell.  It was way off on the specific gravity, like water - not even registering on the specific gravity tester.  I took it back in the next day and told them.  They put their crappy tester on it and said "It's fine".  I insisted they take it back. They eventually did.

I then went to a competing auto parts store to get a similar battery, (different brand).  I asked them to test the battery before I take it, after relating my previous experience to them.  They pleasantly concurred.  They and I were horrified to see that six of their seven batteries they had in stock were bad to start with.  I took the seventh.

What I'm saying is, you could have gotten two lemons in a row.  It probably has nothing to do with where the battery is in your string.

Keith Cress
kcress - http://www.flaminsystems.com

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