Charging Batteries With Generator

[want-a-be]

I posted this once and I think there was a snafu with the site! I had some answers but can get them.
I have a Pheaton with a Magnum Energy system, I programmed the generator to start when the volts are low but I don't know how long to let it run. I have 6 batteries, there is a chart that I can go by if I knew battery amp hrs capacity but this is what I don't know?
Thanks for any and all comments

[time2roll]

I agree with just two hour run time. So what if it cycles a few times a day while in use.

For storage I go back to solar if the RV cannot be left plugged in. Otherwise you might be running that generator 10 hours every two weeks.

[JimM68]

FuzzyKnight wrote:
It would be much better and faster to run the coach engine. 130-145 amp alternator.

No, I don't think so.

His magnum is probably a 2012 or better, at least a 100 amp battery charger, on the little 3 cylinder diesel onan, MUCH more efficient than running the coach engine.

When we boondock, which is basically at nascar races, I run the genny for 2 hours after breakfast, and 2 hours during dinner. Those 2 hours will bring the system from bulk charging to absorb charging (basically 80% charged)

Doing the absorb phase on the genny is probably not an effective use of fuel or noise.

[FuzzyKnight]

It would be much better and faster to run the coach engine. 130-145 amp alternator.

[lhatton]

Yep, I have one. Very nice tool. There are means to determine SOC using voltage, temp and load, but then again you'd need a meter to determine load. If voltage is all he has he'll have to make an educated guess. He can always adjust that run time when he sees results.

The assumption was that he would charge using the grid when he could and use the generator when he couldn't. In that case 50% to 80% is the place he'd want to be while off grid.

The generator is no less capable of that last few percent, it just isn't worth the run time... thus 50-80%.

[Shadow_Catcher]

For long life of rather expensive batteries it is necessary to bring them to 100% SOC (state of charge) with some regularity and keep them from going below 50% SOC. To do this accurately you need a battery monitor, either Victron or Trimetric. See http://www.solar-electric.com/deep-cycle-battery-faq.html
Using voltage as a measure is NOT accurate.
Getting to 100% SOC is hard using a generator as they will have difficulty getting that last few percent.

[lhatton]

50% discharge (-300ah) wouldn't take 300 hours. 6 hours if you could keep it at 50 amps. More like 8 considering you wont be in bulk mode on the last 20%.

Key is to make your charging be "bulk" charging.

You don't want to be below 50% SOC and you will be in acceptance charge above about 80% SOC. So with a 100A charger and a 600ah battery bank two hours should get you from 50% to 80%.

80 to 100% can take a while and is not a very efficient use of diesel or genny time.

Les

[mena661]

Crabbypatty wrote:
The other question is what is the charging output ? Exp if your 600 amp batts are 50% discharged and your only charging at a 50 amp rate, you need to run the genny 6 hrs. 6 x 50 = 300.

It will be more than 300 hours. That last 10% takes as long or longer than the first 40%. To the OP, you don't want to fully charge batteries on generator unless that's your only source for charging (ie you don't have access to shore power). WAY too much fuel to do that. Cheaper to spend a few days at a full hookup campground.

[Crabbypatty]

The other question is what is the charging output ? Exp if your 600 amp batts are 50% discharged and your only charging at a 50 amp rate, you need to run the genny 6 hrs. 6 x 50 = 300.

[cochise49]

I have the EX-30 unit on ours and I believe it will shut down when the battery is charged or at a set time. haven't played with it much yet.

[time2roll]

6 batteries is close to 600 amp hours. Some more, some less.
Battery group number or model number would help.

For storage I recommend 100+ watts of solar.

[2oldman]

..or look that up on the internet.

[rgatijnet1]

There should be labels on your batteries that give that information.