Chassis battery charging when parked

Oh I do have a clamp on ammeter, and never even thought to use it to check for a draw!

If you don't have any better option both of these ideas might help but both have issues.

A spark doesn't necessarily mean there is a issue. There can be capacitance that initially draws power then doesn't. Plus disconnecting a circuit can cause a reset condition when reconnected. The sparky test can be misleading as to any potential issue. MAYBE helpful.

A glowing bulb also doesn't mean there is a problem, as it's a low amp device in series and has significant voltage drop and can (and likely does) change how devices on the circuit work if they work at all relative to trying to resolve some issue.

An ammeter is the best solution of course. A clamp on ammeter is the easiest to use and doesn't change the circuit at all. See if you can borrow one, but both are very useful devices to have for cars and RVs.

I like both of these ideas! Thank y'all a lot.

A great diagnostic trick is to remove the negative terminal from the battery then put an incandescent light bulb like an 1156 on jumper cables in between the negative battery post and negative cable.

If there is a load, path to positive, the bulb will begin to glow.

Then opening connections one by one will show you the culprit when the light goes out.

Try something free first. Remove the neg. battery cable from the charged chassis battery, then touch it to the neg. post. If you see a spark you have amperage flowing, which means a drain somewhere.
No spark, time for a load test and a specific gravity test of each cell.

This is all good stuff! Thank you! I've got the chassis batteries a'chargin' right now. Once they are full, I'm going to disconnect them and see how long the charge holds. And now that the Trip-L has been mentioned -- I had that an my old Bounder, and I think that sounds like a good upgrade for this RV.

Thanks for all the help.

P.S. I'm going to be posting a few photos of some electrical stuff that I don't know what is....

Parasitic draw on my Elantra car is about 2 amp-hours per day. I acquired a 2 amp charger, added a mechanical timer, and charge for 1 hour per day, when I store the car during longer RV trips. My battery is still in good shape (as in will start the vehicle at -25 C) and is the OEM from the maker in 2013.

I do use a Trik-L-Start for the class C chassis battery, powered by the solar panels. It allowed my starter battery to survive for 12 years.

Thanks to BFL13, the SiO2 battery for the Yamaha 3000 Sieb, is also being maintained by the solar. He found a relay that isolates the SiO2 unless the source voltage is 13.5 or higher. That means during use trips, I can leave the remote electric start turned to standby without having the Generator Battery die.

One problem with the Trik-L-Start is that they refuse to ship to Canada. I don't understand why. That's why I ended up with the relay for the generator.

Since every coach setup can be substantially different, the above post is not helpful at all. The engine battery going dead does not mean your batteries have issues. Parasitic draw can kill engine batteries in days or weeks if there is no parked charging setup. Both my last coach and my current coach have no provisions for keeping the engine batteries charged while parked. The last coach I would hook up a portable charger if I was going to be stationary for a few weeks or more. This coach I added trickle charger that sends juice to those batteries anytime 120V power is available.

The chassis battery should remain charged for many weeks to start the engine just like a car. You have a problem. First step is to load test the battery, free at most auto stores.

How old are the batteries? A diesel will have 2 engine batteries. If they are nearing 5 years old or older they are due for replacement. Replace both of them with AGM, AGM’s last a few years longer than traditional flooded cell batteries.