Charging Batteries With Generator

[Scraper]

Have ours in storage for winter, thinking it would be good to go start up the generator and charge the house batteries to keep them up. How long to run the generator to full charge (let’s estimate they are halfway rundown)? How much propane (lb/hr) will the Onan 5500 burn only charging the batteries with no other load?

[almcc]

Not sure how your unit is wired but on our 2013 there were circuits that bypassed the battery cut off switch so that the battery discharged after about a month without the RV being connected to shore power. I rewired so that once the battery switch was turned off there were no phantom draws. A fully charged battery will retain a charge over the winter without needing a recharge that way.

[Scraper]

Originally Posted by almcc

Not sure how your unit is wired but on our 2013 there were circuits that bypassed the battery cut off switch so that the battery discharged after about a month without the RV being connected to shore power. I rewired so that once the battery switch was turned off there were no phantom draws. A fully charged battery will retain a charge over the winter without needing a recharge that way.

Thanks for that. I do open the main disconnect and turn off the inverter, assuming that everything is disconnected from the batteries. I just thought that the batteries would run down over time.

[drj564]

I completely agree with almcc. I think Redwood has to have some systems that are always energized for safety reasons like the emergency brake switch on the the pin, but that’s just a guess. Not that that switch would draw power but you get the idea. I did the same as almcc and also put another cutoff on the inverter side. There is always a power draw from the inverter even if off. Before I added the cutoff I disconnected the battery cables.

As far as charging the batteries, it would take quite some time to completely charge them. I’m guessing a few hours. You will probably get there and they will be completely dead. If it were me, I’d pull them out and take them home and put them on a charger if you have the means.

[almcc]

The "acid test" (at least on our unit) to check was the CO/propane detector, it was connected to go around the battery cut off, probably the legal folks at Redwood required this. For us in the north country it's important to ensure that the battery doesn't get discharged, as you know the acid in the battery gets changed to water as the battery discharges and the battery will freeze and crack open if it's cold enough.

[travelin' texans]

If your batteries have discharged to 50%, or more, more than once then they're likely done for. I'd suggest remove them, take to your favorite auto parts store & have them load test them. If then they're worth saving take them home, check water levels, topping off with distilled water & recharge them.
In the future when unit is stored either remove them storing at home on battery tender checking water levels monthly or at least remove the negative cable from the battery going directly to ground, or add a disconnect to that cable, that will totally disconnect all DC power.

[XCMARK]

you could install a battery disconnect switch right off the batterys and your lead acid batterys would be Ok for 3~4 months assuming they are at or near 100%soc.

Option 2: you could install a single solar charger and use one of the folding 120W + panels on the sunny side of the trailer and only have to install a simple 5 wire connection solar charger in your storage bay. Battery + and - and solar + and - and a ground to the body of the solar charger. You could make this system much more capable if you wanted or as simple as you wanted.

option 3 : install a victron BVM 712 battery state of charge meter , in this meter there is a relay that is programable to be able to start your generator as the battery are drawn down . You can program it for 55% state of charge (SOC) and turn off at 100% SOC. this would be automatic start and stop as long as you have fuel.

the problem with lead battery is they need to be fully charged time they are drained, if not the lead plates for sulfur deposits and this will over time shorten the life of the batteries. To remove most of the sulfur you need to run your battery's through a disulfate phase a few times and then top off the water in the battery's. Basically, your putting higher voltage and low amps into the battery and causing the acid to warm up and bubble. when this is being done its cleaning the plates and causing some acid to boil off into vapor. The absorsion phase of charging is very important to long battery life. I found my Magnum inverter has 3 types of charging if you use it rather than the power converter. The magnum does float, bulk and equalize. Equalize can do two things for you , it brings multiple batteries to full charge assuming they are not all at the same state of charge and it helps disulfate the battery's by raising the voltage slightly during the phase. You need to program the magnum for your battery type and battery bank size that is very simple to do and once its done you just leave it on and turn off the power converter at the 15 amp breaker.

[XCMARK]

My proof reading has got to be more effective, I cannot edit my post now that its few hours old.....

[Eugene_Elder]

I run my Generator every 2 weeks for 2 hours. My lead-acid batteries seem to be maintained by doing this. Always remember when doing this to turn on your A/C while running your Generator. Doing so puts a load on windings which is good for the generator. I will soon be installing 6000w of Inverter, 1600 watts of solar, and 4800ah of LiFoPo4 batteries at which point I will change my Lead-Acid bank to only a single LiFoPo4 at that point I will only exercise every 2 months for 2 hours. Good luck to you.

[Scraper]

Checked yesterday and I had 12.6v when I switched on the inverter, so I think I’m good. Hadn’t had the camper out since October so it appears that when I turn off the inverter and the main disconnect, I’m sufficiently isolated so they will stay charged.

Ran into this info at https://homebatterybank.com/do-car-batteries-freeze/

“A car battery will freeze if its state of charge and the temperature are low enough. A fully charged battery at 12.7 volts will freeze at -70°F. A half-charged battery (12.0 volts) can start freezing at 5°F and a fully discharged car battery (11.5-volts) will freeze at 32°F.”

Thanks everyone for responding! Come on warm weather!