Community Forums

Dan McMartin · 06-21-2017, 04:44 PM

I'm slowly learning about batteries and RV electrical. But I have a question. Let me lay out my sort of theoretical circumstances.

I've got four 6v 225AH wet cell batteries, as opposed to AGM's. So I've got 450 total amp hours at 12v and about 225 usable amps. I've got a 45 amp charger controller. I've got a 5500 watt Onan Gennie and a 3000 watt portable generator. I use about 150 amps a day. I've got no solar and I'm boondocking.

I'm thinking the charge controller is the weak link in this set up if I want to minimize generator time. The generator, I assume, can deliver plenty of power. The batteries being wet cell have a limit too but can take more than the charge controller is dishing out...at least for part of the charge cycle.

I think I'd be better off with a 60 amp...maybe even higher...charge controller. Or am I off base here?

vsheetz · 06-21-2017, 04:53 PM

Is it a multiple stage charger? If yes are you getting to float? If not, the batteries are not fully charging. A higher amp charger can reduce the bulk charge time and get you to absorption and then float sooner. If your charger is not a good multiple stage charger I would get in that is and while at it up the amp capability.

Steve Kiemele · 06-21-2017, 05:42 PM

Regarding your 450 AH total capacity, only about 225 AH is really available for use without damaging your batteries.

Yes, a higher capacity charging system will work faster. I have a similar battery arrangement and my inverter can charge at up to 100 amps.

Know that your batteries accept lower and lower rates of charge as the "fill up." Anything more than your 45 amps would not be used once your batteries reach about 85% state of charge. You could go from 50% to 85% much faster with a better charger.

powercat_ras · 06-21-2017, 05:47 PM

Quote:

Originally Posted by Dan McMartin

I'm slowly learning about batteries and RV electrical. But I have a question. Let me lay out my sort of theoretical circumstances.

I've got four 6v 225AH wet cell batteries, as opposed to AGM's. So I've got 450 total amp hours at 12v and about 225 usable amps. I've got a 45 amp charger controller. I've got a 5500 watt Onan Gennie and a 3000 watt portable generator. I use about 150 amps a day. I've got no solar and I'm boondocking.

I'm thinking the charge controller is the weak link in this set up if I want to minimize generator time. The generator, I assume, can deliver plenty of power. The batteries being wet cell have a limit too but can take more than the charge controller is dishing out...at least for part of the charge cycle.

I think I'd be better off with a 60 amp...maybe even higher...charge controller. Or am I off base here?

Yes, you should go with a bigger charger controller and your batteries will charge to 80 % faster. Once they get to 80% the controller will drop out of Bulk Charge mode where it pushes the Max Current the Charger can put out and go into Absorbtion Charge mode and the 80 % and up phase won't go any faster.

I replaced my OEM 45 Amp with a PowerMax PM3-100 100 Amp max output controller, about $ 150, and it cuts my time to boost my batteries to 80 % to half what it was before. For a 100 Amp output, use at least 2 AWG cables.

twinboat · 06-21-2017, 05:53 PM

The recomended wet cells charging rate is 13 to 15 % of AH capacity.

A 60 to 70 amp charger, wired with the proper gauge wire, will get your batteries charged safely and fast.

Any more then that could cause exess heat and gassing, if starting out with a low state of charge.

You can use 80% of your AH capacity without damaging your batteries. You will shorten their life by half, compared to using 50 % capacity, but that's the cost of doing business.

More capacity or more frequent replacment.

Dan McMartin · 06-21-2017, 09:20 PM

As I suspected. As I said this is theoretical at this point. Just trying to see if the manufacturer (Newmar) will swap in a higher amp charge controller but no sense if it wouldn't speed things up.

Quote:

Originally Posted by twinboat

You can use 80% of your AH capacity without damaging your batteries. You will shorten their life by half, compared to using 50 % capacity, but that's the cost of doing business.

Seen that. I think 50% is the optimal point to balance capacity with longevity but on the other hand, if you plan to swap out the wet cells for AGMs or Lithium at some point, why leave life in your cheaper wet cells.

And that's what we intend to do. That and solar.