Battery Disconnect??

I posted this in a brand-related Sprinter forum, but wanted to float it here too, for a wider audience.

I put my 2013 Airstream Interstate (3500 Sprinter) into storage last week. Not connected to shorepower at all... I followed the manual for disconnecting the chassis battery at the connector near the throttle pedal and left it in that condition for about 10 days.

I went by today just to check everything and got a surprise. I hit the unlock button on the keyfob out of sheer habit. It unlocked???? Then when I got inside I noticed the dashboard display was on, showing mileage etc.... I went back to the power control center in the back of the RV and noticed I was getting a voltage reading on the chassis battery (Sprinter side of the circuit). I am wondering just what gets disconnected at the ground post that was indeed disconnected.......or was I possibly getting power to those circuits from the coach side of the battery isolator in the RV circuit.

Any thoughts out there in general Sprinter-land?

BTW...The voltage indicated on the power center was exactly the same for both the coach battery and the chassis battery.....making me think there was feedback into the backside of the chassis circuit.

Almost certainly, your vehicle is being powered by the coach battery. Your chassis battery is not in the loop. What kind of battery isolator do you have?

The Battery Isolation Manager is from Precision Circuits Inc.

Do you have solar? If so, that explains it:
1) The solar controller is keeping the house voltage at "charge" levels.
2) The BIM sees that the house is charging and that the chassis (having no battery and thus no voltage) needs charging.
3) So, the BIM connects the two systems in an effort to charge the chassis battery from the solar source.
4) Therefore, the house battery is connected to the chassis systems, powering them.

Makes sense. That is exactly how the BIM is supposed to operate. Tomorrow I will reconnect the chassis battery and confirm this has not caused any issues with the Mercedes electronics. I doubt that it has, in that I am not the first person to disconnect this way....and it hasn't been raised as an issue in any of these forum threads. Thanks for the extra pair of eyes on this issue.

toskeysam said:

Makes sense. That is exactly how the BIM is supposed to operate. Tomorrow I will reconnect the chassis battery and confirm this has not caused any issues with the Mercedes electronics. I doubt that it has, in that I am not the first person to disconnect this way....and it hasn't been raised as an issue in any of these forum threads. Thanks for the extra pair of eyes on this issue.

Click to expand...

DO you have solar? If so, he's correct about what is going on. But if not, why is the coach battery still connected? You will wind up with all the batteries dead eventually, if nothing is charging them and no master disconnect on the coach battery.

The Airstream Interstate does have a solar panel. The voltage I was reading was the charging voltage from the solar controller. What surprised me was the fact that parts of the chassis circuit were still going to be active, but in retrospect it makes sense. The Airstream Interstate does not (UNFORTUNATELY) have a factory-installed disconnect switch for the coach battery. Several owners have installed after-market switches.....