Some questions

[JimT]

(01-09-2020 )tree98 Wrote:  Take them out and have them tested at a truck parts store. They can find which one is bad. If they are all the same age and are old, just replace them all.

I just finished replacing mine. They were about 17 months old and all of a sudden the charge was dropping overnight. If i used the battery disconnect to cut off power that would help, but after a couple weeks even disconnected they would drop too low. luckily I had used the time to find a good deal on amazon and the new ones arrived just as the old ones got bad. replaced all four and haven't bothered to test the old ones yet. i'm pretty sure, like the OP, that one or more have a bad cell. I don't have an APU so these batteries have been cycled a bit (they are combo deep cycle/starting AGM), so with over a year of abuse I figured it would be wiser to replace all four.

OP, at 160amps you need to be careful with how much load you put on the system. If your electronics are drawing a lot of power (fridge, speaker amp, lots of lights, tv, etc...) and you run the batteries down when the truck is off, then 160 amps may not be enough to power everything AND properly recharge them while driving around. This will shorten the useful life of the batteries and put a lot of stress on the alternator. Adding another battery will give you longer reserve capacity, but it will also increase the load on the alternator.

A good shop should be able to test the batteries and load test the system to see if the alternator is both functioning properly and able to supply the demand for the entire system.

Be careful about using a parts store to test the batteries. The correct way involves charging them fully then testing, which could take a full day. Many parts stores will test batteries for free... and what a shock, they tell you it needs to be replaced!