Hoping I can get a second opinion, or multiples
before i tear into the Battery Conrol Center on my Thor Vegas.
First, we rarely boon-dock so this was the first time in a while that we have had to run on house batteries. And for the record, the house batteries are 9 month old Battle Born Lithiums. The chassis batter is also less than a year old. We pulled up at my in-laws driveway, parked and set up as usual and all seemed well. It was warm so the fans were runing along with the lights. About two hours later the lights flickered a couple of times. Then a couple of hours latter the Vegas went dark! First reaction was to go for the generator. Nothing there even with the emergency start switch. Next was to start the engine. NOTHING THERE EITHER! Sitting in the drivers seat could hear one of the solenoids in the BCC clicking away every few minutes. Luckily we were boon-docking in a drive way (we live a rough life!) and so a couple of extension cables and a few cuss words later, we were back with 15amp shore power, the lights were on and the fans ran. Woo Hoo! we got a goon nights sleep and decided to trouble shoot it in the AM. I woke at about 3am with the big question. Why did the chassis batter die? Its not supposed to be able to feed 12v to the coach - right? Isnt there something that is supposed to disconnect the chassis battery from the coach system but let the coach charge the chassis battery when on shore power? I think that is how its supposed to work so my next thought was ..... BCC or some relay somewhere wasn't wanting us to go to sleep that night!
Next morning I embarked on some diagnostics with my trust meter.
With Shore power ON, Engine OFF volts to chassis battery was 13.4 and volts to house battery 13.4 - conclusion was that the charge in the coach was doing its job and charging both battery sets.
With Shore power off and Engine ON volts to both batteries was a little higher ~13.7 but matched. - Conclusion was that the alternator was charging both battery sets.
With Shore power OFF and Engine OFF the voltage on Chassis battery was at 12.7 so not bad, and the lithiums were at 13.1. - Conclusion, the batteries were OK and not fried.
Next step was to pull out the amp-clamp to see if a parasite load was pulling the chassis battery down. I dropped the clamp on the chassis batter positive lead and saw it was pulling less than .01. I got the same reading on the house battery feed cable. I thought that was maybe a coincidence and so I put some loads on the coach battery by putting the fans and lights on and, as it should, the amp draw went up. I then pulled the clamp off the house battery and put it on the chassis battery. I got the EXACT same load reading. - AHHA - i don't think it is supposed to be like that - is it?. This would explain why the chassis battery died. I think the chassis battery is powering the coach! So. All of this to say, I think the gizmo in the BCC is not isolating the chassis battery when the coach is boon-docking. Before I rip the BCC out and start tinkering with I thought I would run this by the collective wisdom and see if I am on the right track, totally misunderstand how this stuff is supposed to work or missed something so obvious I will be red faced and feeling like the idiot I am. Any thoughts that can help are welcomed! - Thanks
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