BIM (Battery Isolation Manager) Question

[FEZ]

Hi All,
Quick question, I have a 2017 Thor Miramar and I have replaced my chassis battery back in December '18 and now that battery has gone dead too but is still rechargeable. I'm 99% sure the BIM is bad. So my question to the group is, what can drain a battery besides an alternator and BIM? Also, this fall when I went to put it in storage I had to jump the battery and drove it for 15-20 minutes to my storage area and week later I was able to start it without jumping/charging it. This leads me to believe the BIM is bad. Any thoughts? Thanks in advance!

[16ACE27]

Alternators charge batteries.
BIMS connect two batteries (or battery banks) together when one side is charging and separate them when neither side is charging.

A BIM with an internal short MAY discharge a battery.
An Alternator with an internal short MAY discharge a battery.
Anything connected to the DC buss will discharge a battery if energized.
Anything connected to a DC buss MAY discharge a battery if faulty.

Does that answer your wide open question?

[FEZ]

I know what each part does, but thanks. I just want to know if anyone else has experience almost the same thing and did a BIM cure the issue. Trying not to chase something forever. Thanks!

[16ACE27]

Put an ammeter on your chassis battery with everything turned off. The only draw would be in milliamps for maybe the memory in the radio. If you have more than that lift the lead on one suspected component at a time to see if the draw stops. If your case the BIM and or the alternator. If neither one of them are the culprit then it's a major guessing match. I'd move on to the major fuses and relays in the fuse box next.

[FEZ]

I will attempt that. Hopefully I will figure it out quickly. Thanks.

[16ACE27]

Wish I could be more help and I hope it's not an intermittent problem. You can't fix it if you can't see it.

[halfprice]

Call the bim manufacturer info below.

The bim has a 5 year warranty. A tech will walk you through several tests to determine if the bim is the problem

To do the tests you'll need a volt meter and access to the bim. For me that meant crawling under the mh to gain access

The tech was very helpful and my bim was not bad but he helped solve my problem

Jerry

[revjeffrey]

I did exactly as Jerry said above. Mine was bad. All good now. I still disconnect batteries if I will not be using rig.