Coach battery issue!

[redantair]

Hi fellow interstaters....I have a problem and I have read through all of the threads and this is where I am (i'm calling the dealer tomorrow for some help).

We are in the middle of a road trip and have stopped in Colorado and staying at a hotel for a couple days. I went out to my 2014 Airstream Interstate today and there is no power to the coach electrical stuff (radio is dead, no lights, generator won't start etc - solar readout shows nothing etc). I check the battery voltage in the panel and it shows 14 something for the chassis battery, but only 5.4ish volts for the aux battery. After reading some posts, I assume the coach batteries have somehow discharged, so I remove them from the back on the slide tray and plug them up to an AGM charger/tester, and they show 15+ volts. So now I am confused. We've previously parked the AI for a couple of days with no problem with the unit staying charged.

(Also, would the alternator not charge the batteries if I drove them around or did I really need to bench charge them?)

Anyone have any idea of what's going on or where to point me in the right direction?

Thanks in advance.

[73shark]

Yes the alternator should charge the coach batteries when the engine is running. As to the other problems I don't have a clue. It seems like there are a bunch of electrical problems with these various Interstates. I know I've had my share of electrical problems.

[Protagonist]

Originally Posted by 73shark

Yes the alternator should charge the coach batteries when the engine is running. As to the other problems I don't have a clue. It seems like there are a bunch of electrical problems with these various Interstates. I know I've had my share of electrical problems.

I ran into this early in my Interstate ownership. If the house batteries are above 10.5 volts or so (don't know the exact figure) the alternator will charge them. But if the house batteries drop too low, there's apparently some relay that disconnects the house and chassis systems, and the alternator will no longer charge the house batteries. I think it's some kind of safety feature to make sure that a problem on the house side doesn't affect the chassis systems.

My house batteries didn't get down to 5.4 volts, but getting down to 8.5v or so was bad enough. I ended up recharging my house batteries on a bench, using a good multi-stage charger over the course of about two days each.

Solar won't work when the batteries get too low, either. The charge controller doesn't run off the panel, it runs off the batteries. So if the batteries get too low, the charge controller quits working and the solar panel can't charge the batteries.

Most of my electrical problems have NOT needed repairs, just a more complete understanding of what systems are draining the batteries while the unit is stored, to make sure those systems are shut off.

[Lily&Me]

Originally Posted by Protagonist

Most of my electrical problems have NOT needed repairs, just a more complete understanding of what systems are draining the batteries while the unit is stored, to make sure those systems are shut off.

Agreed.

Stating the obvious, maybe something has accidentally been left on or the little switch that sets the battery to "use" and charge has inadvertantly been turned off.


Maggie

[wayneskid]

Originally Posted by redantair

I check the battery voltage in the panel and it shows 14 something for the chassis battery, but only 5.4ish volts for the aux battery. The coach batteries should never go that low; they will be damaged if they do.

...so I remove them from the back on the slide tray and plug them up to an AGM charger/tester, and they show 15+ volts. So now I am confused. We've previously parked the AI for a couple of days with no problem with the unit staying charged. If the charger/tester is in charge mode, this would make sense. To avoid confusion, read the voltage with a DVM. A decent DVM is an essential part of your tool kit.

(Also, would the alternator not charge the batteries if I drove them around or did I really need to bench charge them?) Yes, the Sprinter alternator WILL charge your coach batteries, UNLESS your battery isolation manager is bad. I had this problem with my 2010; took multiple trips to various dealers and months to get diagnosed and solved. I finally convinced AS to send me a new BIM which I installed myself.

Good luck getting this sorted out!