2 battery system question

[RaggedyMan]

I'm not familiar with the 2 battery setup and/or a generator and I realize it's not some magical or complicated thing, but can something in the system drain one battery and not the other? I ask because I have one new battery (both are interstate blem's and relatively new) that lost all charge over the weekend and the other is fine. I have it on charge to see if it will take it but I don't want to use it if it's going to randomly fail nor do I want to get another (or 2 proper batteries) if something in the system is causing this.

 

[tim292stro]

A 12V tap can yes. Do you have any 12V items in your truck?

 

[RaggedyMan]

I have no 12v items in the truck.
I'm not too sure it's even taking a charge but it's only been an hour or two, I don't know I'll be able to trust it even if it does. I'll probably just go buy two correct size batteries like it's suppose to have and be done with it but I don't want to do that yet if they could be ruined because of some other electrical problem.

 

[emr]

There are a few recent battery posts that will answer all ...

 

[tim292stro]

I have no 12v items in the truck...

If you don't have any 12V taps at all (simple single wire jumper from high negative post to low positive post), it's likely one battery has bad cells. Separate them and measure the voltage - if either is under 11Volts it has a bad cell(s). You can try charging it but use a load tester on it after you do. It may never get to full charge, and it may not be able to support any kind of load (think starting). If you do have to replace batteries, it's best to get two that are the same age so they charge and discharge about the same. Put a new battery in with an old one and it'll adopt the old battery's charge/discharge profile (short life) - also if you get new batteries, charge them fully out-of-frame before installing them in the truck.

There are a few recent battery posts that will answer all ...

These probably describe using a load tester to verify the health of your batteries. Good tool to have, Harbor Freight sells the common one cheap.

 

[Akicita]

If you have two batteries, make sure the bridge between the two is tight around the terminals and none of the cables touch anything metal other than their terminal.
I attach pictures of my setup. I have two car batteries installed. Never had a problem with them.