Returning Batteries to MH After Long Storage

[Bill Sprague]

A member, that I have not met before, called me yesterday to ask advice.  

He removed the chassis batteries for a few months of storage.  The house batteries are AGM and stayed in place.  The motorhome is an '01 Patriot.  It has been without any power or use for about 3 months.  It was not plugged in, nor was the genset run.

His plan is to charge the chassis batteries at home, return them to the motorhome, start the genset and let it run to charge the house batteries.  "Shorepower" is not available where the motorhome is stored.  

I am not sure where the genset gets power for the starter.  I once asked a Monaco tech at a rally and he said it could be wired to start the MH off either the house or chassis batteries.  

I told him I had never done this, advised he be sure he knew how to connect the chassis batteries and give it a try.  

Should I have suggested a different approach?  

[Edward Buker]

Bill,

 I think the most likely scenario is that the genset uses the chassis batteries to start. If those are charged then he should be able to start the genset if wired this way. One caution is that there usually is some sort of coupling device/echo charger that couples the house to chassis batteries. There may be solar power charging taking place and when the chassis batteries are disconnected so you should tape off or tie wrap the chassis plus lead so that it cannot inadvertently hit ground on the battery frame just in case the house battery bank is seeing enough voltage to engage the coupling circuit while in storage.

Later Ed

[Robert Mathis]

Alternatively, he can replace the chassis batteries and if the genet starts off the house batteries, use the battery boost switch to get it running. In either case, I would first start the main engine, let it run to make sure the chassis batteries are topped up, then start the genset. He could even use one of the chassis batteries to jump off the genset with jumper cables. The genset doesn't need that much power to start it.

[Bill Sprague]

Thanks for the help.  I've not considered a rig with completely dead batteries.  

I'm traveling with Gerald Ferris on the Seeking Southern Comfort Rally and he concurs.  I phoned him again today and relayed that the genset should start, it will take a few moments for the ECM to boot, that the genset should run 3 or 4 hours for charging the house batteries, not to run the engine until the house batteries are charged and to be sure the chassis batteries are hooked up correctly.

[MarcRodstein]

It may take more than 3 or 4 hours depending on how flat the house batteries are.

[LarryNCarolynShirk]

If you start the engine first, the house batteries will put a large load on the engine alternator, which will overheat and reduce the life of the alternator, or burn it out.  It is better to start the generator first, and let it produce the 120 v to charge the house batteries through the invertor/charger.  After the house batteries are charged, you can start the engine, with or without the generator running.  There will be less load on the engine alternator this way.

Larry

[Keith Oliver]

"He removed the chassis batteries for a few months of storage.  The house batteries are AGM and stayed in place.  The motorhome is an '01 Patriot.  It has been without any power or use for about 3 months.  It was not plugged in, nor was the genset run."

My experience with AGM batteries is that 6 months left without a charging source will not be bad for them.  Mine routinely goes that long, as it is the start battery for the outboard on my dinghy, which is abandoned on the back of my boat from October to April every year.  I put a charger on it the first year, but after that I haven't, and now I expect it to start the outboard on the first crank after a long layup and I haven't been disappointed.