Coach battery not holding charge

was_butnotnow wrote:
The coach batteries are the chassis batteries. My thought is if the kill switch is turned off no power should be used for anything on the chassis. The 4 new AGM house batteries are charged by a solar controller 600 W solar and Magnum 2000 w PSW charger/inverter. We are plugged into 50 A as a camp host site.
We do have a cell phone charging off the 12 v dash cig plug in and wondering why that works when the kill switch is shut down that controls the chassis power.

was_butnotnow,
First off, your coach in in the '05 era. In many coaches, even and especially the diesel ones, the CHASSIS batteries were neglected from the shore power charging system. For some odd reason, many manufacturers deemed it not necessary for the chassis batteries to be charged while on shore power.

So, with all that being said, are you DEAD sure that your chassis batteries are being charged while on shore power? You state you have 600 watts of solar. Well, that's a ton of solar and while I'm not a solar expert, I'd just about guess that, that system is capable of around 20 amps of charging or more.

Your Magnum 2000 watt PSW Inverter/Charger will automatically adjust what it needs to send the house/Coach batteries when they have different amount of voltage present. The lower the voltage, the more the charger side of that magnum unit will put out. The higher voltage it sees, as in the house batteries are topped off, that charger will drop right down to a maintenance/float charge.

This is all in coordination with your roof solar. If it's supplying most of the charging for your house batteries, the Magnum will back down as, it sees no need to supply higher amperage for batteries that are already receiving it. Now, just because you have your chassis batteries switch shut off, that doesn't mean there isn't parasitic draws on on those. There will always be parasitic draws.


In this situation, I'd first get those chassis batteries load tested for prolonged load carrying capability. Then, it they check out fine, then make sure all connections are clean and tight and that also includes an often neglected one, the negative cable ends that normally attach to the frame. Those can get seriously corroded and rusted.

Once all the connections are clean and tight, then you need to determine IF, your Magnum Inverter/Charger is has been set up to send some amperage to the chassis batteries. For us Winnebago and Itasca owners, the same era coach as yours did not have any chassis battery charging from shore power. Winne started adding what's called the "Trik-L-Start" units in early '06 to remedy the dead chassis battery situation after even short term storage. But, any coach prior to that, had no means of charging the chassis batteries while on shore power.

So, this is why I suggest that you may NOT have any chassis battery charging unless an independent charger has been installed. I think I recall you mentioning a 2A unit. That's not much if the chassis batteries are used for purposes that running the engine etc. Things like the steps, slides, and other items. So, these are some things to check. Good luck.
Scott