Community Forums

CCRyder 505 · 03-08-2019, 12:21 PM

Just for keeping the batts charged, and not running the 12.5kw on board for that, I am also looking at the Predator genset. This is only for batt upkeep at night. We have a residential fridge plus other parasites in the background

So the question is do you folks with an outside genset charge your AGM batts with a standard charger, or is there a charger I need to use for AGM batts? Only need to put 3-5 amps into the batts, continuous. Have two large 12v AGM.

BTW, for boondocking only.....

Thanks

theoldwizard · 03-08-2019, 02:06 PM

Quote:

Originally Posted by 505 KittyKat

So the question is do you folks with an outside genset charge your AGM batts with a standard charger, or is there a charger I need to use for AGM batts?

Is this a future purchase ? If your RV has a converter/charger that works well charging your AGM batteries, just use that. Not all converter/chargers have setting for AGM batteries.

If you have not spent any money, I suggest you look into a inverter/charger/automatic transfer switch. Newer model have setting for all battery chemistry. Get rid of the converter.

twinboat · 03-08-2019, 02:14 PM

Use a few adaptors to plug the shore cord into the portable generator. Your onboard charging system will keep the batteries charged.

If you turn on any big load item, the generator will probably shut down. Not a big deal, start it back up and don't do that.

If your 2, large, 4D or 8D?, AGM batteries won't run a fridge overnight, you may need new batteries.

jcussen · 03-08-2019, 02:15 PM

Quote:

Originally Posted by 505 KittyKat

Just for keeping the batts charged, and not running the 12.5kw on board for that, I am also looking at the Predator genset. This is only for batt upkeep at night. We have a residential fridge plus other parasites in the background

So the question is do you folks with an outside genset charge your AGM batts with a standard charger, or is there a charger I need to use for AGM batts? Only need to put 3-5 amps into the batts, continuous. Have two large 12v AGM.

BTW, for boondocking only.....

Thanks

Just plug your shore power into the generator, make sure you don't turn on any big loads in the coach. If you can set your inverter incoming amperage, set it down to 15 amps.

CCRyder 505 · 03-08-2019, 03:47 PM

Thanks everyone. The AGM's are 8d. They will sustain the entire night time loads all night. I just don''t want the batts to be at 12.2 very long without some juice coming in to them.

Closer look at the Harbor Freight catalog I found an AGM compatible charger. It is 4 amps and should be enough to keep the batts lively overnight.

So my idea is to have the charger connected to the coach batts and the genset running the charger overnight. The gen will run for 12 hours on low power out.
The price on the genset is now $449.

We have 600+ watts of solar. Haven't done much boon docking. A few times at the Moose Creek Campground in the Gallatin Canyon, Montana. Stayed a couple days with heavy cloud cover. Now we want to explore our Eastern Washington boon docking.

twinboat · 03-08-2019, 03:55 PM

Then you don't need batteries at all !

The purpose of batteries is to discharge and then recharge them.

You can run your batteries down to 12.2 volts over 1000 times before you notice a large loos of capacity.

jcussen · 03-08-2019, 04:04 PM

Why can't you use your coaches built in inverter/charger to charge the batteries?

Mr_D · 03-08-2019, 04:05 PM

I can see not wanting to run your 12.5 gen overnight. I don't do it. I charge for two hours in the morning while making coffee and breakfast. Then again a couple hours before quiet time. In the meantime my 400 watts of solar are working during daylight to top my 4-8D Lifeline AGM's up.
4 amps won't add any charge to the batteries, it might keep them charged if there are no loads on the batteries and they are totally charged beforehand. Your inverter/charger puts out 100 to 150 amps when on the generator.

CCRyder 505 · 03-08-2019, 04:59 PM

I can use the inverter/charger, but the plot behind all this is I don't want to use the 12.5 kw generator at night to bother folks. I think the Predator is quite enough to be ok without too much noise. And, I could use the Predator to the 30/50 amp coach plug with a 20amp adapter. Too much stuff to reset/reprogram on a chilly morning.

So wouldn't the AGM compatible charger (greater than 4amps)work ok on the house batteries?

Mr D, my AGM's are 2015 vintage. Are AGM's like lead acid in terms of age when adding newer batts? I think with lead acid all should be changed when one is bad. So with AGM's could I add two more 8d's to the 2015 year batts or would the 2 older ones need changing out?

twinboat · 03-08-2019, 05:31 PM

A residental fridge will draw 1 to 3 amps at 120 volts.

That's 10 to 30 amps @ 12 volts. That's without the icemaker.

Even if it runs 1/3 the time, it will put you over your proposed 4 amp charging.

What's to reset ? Just start the big generator and run what you need in the morning. The Auto Transfer Switch will switch over to the big generator and the inverter/charger will continue to charge at the lower rate.

CCRyder 505 · 03-08-2019, 06:25 PM

Thanks twinboat. Do you have any comment on the adding new AGM's with older AGM's?

twinboat · 03-08-2019, 07:08 PM

If they were a year or so old, yes, but after 5 years of unknown treatment, I'd say no.

Run them until shot and then replace and add if more capacity is needed.

Don't worry about not going below 12.2 volts with your old batteries, they can handle drawing down to 20% state of charge, 11.7 volts.

CCRyder 505 · 03-08-2019, 10:04 PM

Very light use. Only a couple times dry camping. Other wise the coach is in the garage plugged in. On the road, always in a campground. Only a couple times dry camping for a day or two......

Persistent · 03-08-2019, 10:31 PM

Quote:

Originally Posted by 505 KittyKat

Thanks everyone. The AGM's are 8d. They will sustain the entire night time loads all night. I just don''t want the batts to be at 12.2 very long without some juice coming in to them.

Closer look at the Harbor Freight catalog I found an AGM compatible charger. It is 4 amps and should be enough to keep the batts lively overnight.

So my idea is to have the charger connected to the coach batts and the genset running the charger overnight. The gen will run for 12 hours on low power out.
The price on the genset is now $449.

We have 600+ watts of solar. Haven't done much boon docking. A few times at the Moose Creek Campground in the Gallatin Canyon, Montana. Stayed a couple days with heavy cloud cover. Now we want to explore our Eastern Washington boon docking.

Kitty,
All the posts agree. You do not need to run a generator overnight. That is what the batteries are for.
3 or 4 amp charge to such a large bank is pointless. It will accomplish nothing.
Running 115 volt generator to provide 3 amps of charging is very expensive per amp. Even a 1000 watt generator would be idling.
You already have everything you need. Running the big generator 4 hours a day is probably enough even without the solar.

Sit down with a cup of tea or something, relax, and enjoy.