Will dirty terminals keep a battery from charging?

[The motor guy]

Took my truck to autozone thinking I had a bad battery and his tester said to charge the battery before testing. Anyways, on my truck is has two parallel batteries that have to be charged. Makes me wonder if all the times I replaced batteries that were only a couple years old, it was just a poor connection. They haven't been all that picky until the last couple years about testing them, they typically took my word for it when I said the truck wasn't starting well and gave me new ones under warranty.

 

[JMJNet]

Did you load test them one at a time?

Even if one bad, you need to replace both.

 

[4WD]

Yep - and poor grounds are more common than folks realize

 

[The motor guy]

Did you load test them one at a time?

They unhooked them. Only one could be tested because the other one needed to be charged. I argued with him and said, yeah because it's dead. Anyways it's charging okay now after unhooking them. Thought he was pulling one over on me. Guess he was right.

 

[The motor guy]

Did you load test them one at a time?

Even if one bad, you need to replace both.

Yeah but it seems like it was dirty terminals that was hampering the charging. I do believe the passenger battery gets charged first, then goes to the driver side via a cable in between the two batteries.

 

[ripcord]

Yeah but it seems like it was dirty terminals that was hampering the charging. I do believe the passenger battery gets charged first, then goes to the driver side via a cable in between the two batteries.

Technically, they both get charged at the same time but since the cables to the driver's side add a small amount of resistance (or large if the terminals are dirty) it always sees slightly less voltage and current than the passenger side.

 

[joekingcorvette]

Yes, keep those cable clean. Some cars are really fussy.

 

[bullwinkle]

If the cables to the secondary battery are corroded or loose, it'll never see enough voltage to charge, the primary will take it all (until its' voltage comes up). The diesel GMs with the dual stud/side mount connectors are the best...

 

[TheLastWord]

Some cars are built with a faulty design of ground to a painted connection like a fender wall.

 

[E150GT]

Some cars are built with a faulty design of ground to a painted connection like a fender wall.

Yeah but they still work. How is that ? I personally ground the paint off mine

 

[Chris142]

Of course!

 

[mk378]

GM trucks with dual batteries have both battery ground wires connected to the engine.

 

[The motor guy]

Take number 47: Started the truck up after not using it for a few days. It barely started. Took it to oreillys this time and the guy found one terminal barely on there. I need to cut off the old terminal bolts or something. They're too corroded to tighten properly. They tested the batteries this time, they're good.

 

[The motor guy]

Can't I use a 1/4" cordless impact to spin them off?