BIM question

[VAtom]

My shore power was accidentally unplugged for maybe about three weeks.

When I found out, the coach batteries were d-e-a-d dead, dead, dead.

The chassis battery was also dead; no startee, no turnover, but the power step worked and a few dash lights, as well.

I charged the chassis battery overnight and the van started up and the Magnum started operating again.

1. Shouldn't the BIM prevent the chassis battery from discharging?

2. The BIM is moderately accessible, is there a standard way to test it?

3. If the BIM is replaced, is there a "better" brand or model (Precision Circuits 00-10021-000)?

[Protagonist]

Originally Posted by VAtom

1. Shouldn't the BIM prevent the chassis battery from discharging?

Not necessarily. The BIM is supposed to keep the house system from drawing down the chassis battery. But there might be parasitic drains on the chassis side as well as the house side, and the BIM won't stop those.

Unplugging the disconnect down by the accelerator pedal will stop most parasitic drains on the chassis battery while the van is in storage (but not necessarily all— I haven't experimented to see because my aftermarket Viper alarm system requires I leave my chassis battery connected 24/7; and yes, with the Viper alarm engaged my chassis battery will run down in 3 weeks if I don't drive the van more often).

[Titus]

The Precision Circuits website has a very good page of instructions on how to test the BIM for charging each battery. There is a fuse on the side of the chassis battery, which, if blown, does not allow current to or from the chassis battery. On my 2013 lounge the BIM is under the rear seat. I am becoming quite adept at removing the rear seat (back first, then the bottom). 1/2 " wrench for the back and 7/16" for the seat bottom, if I recall. The BIM allows the engine to charge to coach battery only if it is below a certain voltage. This will not bring the AGM's up to 100% even after a full day of driving. I too am interesting in replacing the BIM with something that provides the charging voltage schedule that the AGM's like. Am not sure if there is such a device.

[Boxster1971]

Titus - the best way to get a proper charge profile from your Sprinter engine is to add a second alternator and a Balmar regulator.
http://www.balmar.net

Unfortunately you can't use the Balmar with the stock Mercedes alternator.

Another option, done by a fellow on the Sprinter-forum, is adding a second inverter under the front seat and run 120VAC line back to power the Magnum inverter/charger to give the batteries a proper charge.


- - Mike
2013 Interstate Lounge EXT on 2012 Sprinter

[amirm]

FYI, I have two chassis batteries in my 2016. According to the schematic and looking at the system, there is yet another battery isolator between those two (located under the driver's seat where the primary battery is). Does yours have two batteries there too and still got discharged?

[Protagonist]

Originally Posted by amirm

FYI, I have two chassis batteries in my 2016. According to the schematic and looking at the system, there is yet another battery isolator between those two (located under the driver's seat where the primary battery is). Does yours have two batteries there too and still got discharged?

For those Interstates that have both a starting battery under the driver's footwell and an auxiliary battery under the hood (not all do; mine doesn't), only the one under the driver's footwell is used to start the engine. The one under the hood is always isolated when the engine isn't running, and only connected when the engine is running. It's meant as a house battery for non-RV conversions such as ambulances and news vans that have electrical requirements when the engine is turned off.

The only way to use the under-hood battery for starting the engine is to hook up jumper cables from the auxiliary battery to the remote jumper posts under the hood. Which is possible in extremis, but may confuse the relay when the jumper cables are disconnected. Or you might be able to remove the relay so the two batteries are permanently connected…

[VAtom]

Originally Posted by Titus

The Precision Circuits website has a very good page of instructions on how to test the BIM for charging each battery.

Thanks.

http://goo.gl/SdCdev