Starter battery voltage drops while charging

[Wyatt-WO]

I’m guessing that my starter battery which is six years old is toast. But just recently I’ve noticed that when I charge it, the voltage starts dropping instead of going up and it does so pretty rapidly.

Any thoughts on something I might be missing thanks

 

[Morich]

Possibly defective charger or reversed connections would be first thought?

 

[Wyatt-WO]

Possibly defective charger or reversed connections would be first thought?

It’s in my signature I guess you just didn’t catch it.

No, the charge controller is working fine it’s charging the house batteries but when I connect it to charge the engine battery, the engine battery starts dropping voltage instead of going up.

I’ve owned this rig for five years now and never had this issue. That’s why I’m leaning towards a bad battery on the chassis side…

 

[Don G-WO]

Try disconnecting the neg. terminal to isolate the battery, maybe there is some feedback causing the problem.

 

[creativepart]

Wyatt, perhaps your battery is now a dead short??? But look at it this way, 6-yrs for any starter battery in any vehicle, let alone an RV, is a pretty rare occurrence.

 

[Morich]

We would need more precise info on where and how the voltages are being taken. If the start battery has a short and voltage is taken at the actual battery, it would seem to be going down whether connected to the coach or not? But if the start battery is low and we connect to the coach but have the leads reversed, THEN a voltage reading taken at the start battery would start going down very quickly.
But that is all very much theory until getting more info on what and where things are done?
If done with remote reading monitors, etc. then that throws more suspects into the game!
We often get some hints at what the problem might be but we really can't do too much good if we don't have details