Charge House Batteries w/ Alternator?

NA8M · October 9, 2016

I will be on the road traveling for three or so days. During those evenings I will be parked at a Walmart or its equivalent. I do not have a working generator. I will be using an inverter to power small stuff in the Class A in the evening.

My question: When I get back on the road in the morning can I switch the house batteries together with the starting battery and have the motor home's engine and alternator charge the house batteries while on the road?

Or would you suggest I bring along a small inverter generator to handle the charging in the morning while getting breakfast and such before hitting the road?

Or maybe get the motor home's generator working so I can annoy the neighbors in the morning?

Thanks in advance for this information. Has this question already been posed and answered? I am sorry if I missed the topics/discussion when I searched the forums.

Bill, NA8M

Barbaraok · October 9, 2016

Would help if you tell us what make/model/year rig you have, along with # of house batteries/type, inverter, etc. We have a DP and our system is set up to keep the house batteries charged as we go down the road.

NA8M · October 9, 2016

It's a '95 Damon. Ford V8 chassis. Two 12v house batteries in parallel. They're Trojan AGMs, I think. The inverter will only run a TV, fan, and my CPAP machine. Lights are LEDs. On the dashboard is a switch to "pair" the house batteries with the starting battery should the motor home need the extra "power" for starting the rig. I have not yet given this set-up a trial run. I'm planning ahead.

Kirk W · October 9, 2016

Unless your RV has been modified by some previous owner, or the equipment isn't working properly, there will be nothing to switch as all modern motorhomes are built with an isolation relay that ties the output of the alternator to the house batteries when the engine is running and then separates them from the chassis systems when the engine is shut down. The only issue might be the size of your alternator as that determines the limit of charging capability.

That switch on the dash is there to cross-connect the systems in order to use the coach batteries to start the chassis engine if that battery should be discharged. If you want to be sure that the that your coach batteries are being charged when you are driving, just measure the battery voltage with a digital meter, then start the chassis engine and measure that voltage again. If it increases the alternator is charging the coach batteries as it should.