Phil,

Your assessment is correct, assuming you have a high amp charger. 125-150 amps that you can find on the larger inverter/chargers is ideal for charging an AGM bank. As you know, you can push as much power as you want at an AGM bank and it will accept it if it is discharged enough, cutting the charge time (and gen run time) significantly. I always want systems I install that are going to have small solar arrays - or none at all for awhile/forever - to use AGMs for this reason. The difference with the high amp charger is stunning.

On the other hand, if you have a flooded cell bank - unless it is HUGE - you get no benefit from the higher output charger since you are limited by a charge rate of 13-20% of bank size(you can argue the merits, but it is in that range).

But, you already knew all this....

Thanks for all the good information.


Larry

The Magnum inverter with a 100 amp charger uses 15 amps and is about the maximum that my Yamaha 2400IS generator can handle and still have a little power to spare for the TV or furnace.

When bulk charging full bore with only the generator (no solar) adding the microwave or the coffee maker to the load will trip the Yamaha overload.

Sometimes I see the inverter/charger punping over 110 amps (even 120 one time) into the batteries. That was in 20+'s degree weather. Maybe the temp compensation allowed it to push more than 100 amps.

Another thing about solar... At night when on the inverter/batteries, turning on the coffee maker, microwave and TV loads at the same time will trip my 250 Amp DC breaker.

But no problem in the sunshine when the solar is contributing enough power upstream of the breaker and batteries to keep the battery/breaker load below 250 amps.

Most times in good sunlight the TV and regular items run straight off of the solar with no hit on the batteries at all. Once the batteries are charged, the excess solar supplies most of the power supply and gives the batteries a rest for the remainder of the day.

Some folks even have relays that automatically transfer the solar production to power water heater elements once charging is complete - saving on propane or shore power.

I imagine for boondockers who are mainly reliant on batteries, this afternoon reduction of battery usage and wear and tear, could also be a contributing factor to battery longevity over time.

quote:

Originally posted by Jack Mayer:
Phil,

Your assessment is correct, assuming you have a high amp charger. 125-150 amps that you can find on the larger inverter/chargers is ideal for charging an AGM bank. As you know, you can push as much power as you want at an AGM bank and it will accept it if it is discharged enough, cutting the charge time (and gen run time) significantly. I always want systems I install that are going to have small solar arrays - or none at all for awhile/forever - to use AGMs for this reason. The difference with the high amp charger is stunning.

On the other hand, if you have a flooded cell bank - unless it is HUGE - you get no benefit from the higher output charger since you are limited by a charge rate of 13-20% of bank size(you can argue the merits, but it is in that range).

But, you already knew all this....

Thanks guys, that is what I thought,Just wanted to know if I was on the right track.
Vern

I don't know where you are but I wish you were near Linville, NC. I have 4 new interstate group 27 batteries that I was planning on using on the A frame of my TT. My TT in already a little nose heavy and I'm having 2nd thoughts about adding another 250+ lbs counting the inverter and a big battery box. I'm thinking I'll get 2 L-16 AGM batteries and put them in the cabinet under the kitchen sink which is just verily forward of the axle. I'm rotating the 4 group 27 batteries ever other week, one in use the other 3 on trickle charge trying to keep them pretty much in balance with each other until I make up my mind what to do. If you were near by I'd give you a price about half what you cold get anywhere else. When I ordered the Trailer I asked the dealer to install two group 27 AGM's When I got the trailer home I looked in the battery box and found that he had put two little ATV batteries (Group 34) in there. I went back down there with some choice words for him and he said I can't get group 27 AGM's but I'll take the Group 34's back and give you 4 new Group 27 flooded cell batteries. So that's how I got stuck with them. I just now got the solar panels and PV controler installed. Have the inverter but I haven't started installing it yet cause It will depend on where I put the batteries. Aframe or sink.

Those 4 Group 27's, (about 400 AH's) would make a nice battery bank, about 200 AH's to burn w/o going under 50% discharge.

From what I see mostly reported here, 200 AH's is plenty for daily usage with an inverter if they're topped off/charged daily.

Sounds like soneone's going to get a good deal on a nice sized battery bank.

AGM batteries are the way to go if you can keep them in the coach / RV / inside, they operate best at room temp, and like most batteries do not do well with constant temp changes.

There is a gentleman in the park here, with solar and AGM batteries, since AGM batteries do not need vented and are designed to operate even if they are upside down, they are very expensive and the reason you find them in modern jets.

You will need a small generator even if you use AGM batteries with your solar power, but a much smaller generator than you would normally use with out the solar. The gentleman I just spoke of has been able to run his ac boon docked, off his battery set up for 18 hours. Those impressive numbers come from the following facts.

His batteries are in the coach so room temp is a constant. He uses two 3000 watt inverters. He has a small generator to charge the batteries if the sun did not come out to play that day or he needs to use more power than normal.

I forgot to add if you know him Bill is his name, he is the man to talk to about solar and batteries, I know he comes online I just don't know his online name or handle, next time he out for a walk I will mention this thread and ask him to come and chat with you about batteries.

His RV was custom made from the ground up, including the frame and suspension and they have been full time for 20 plus years. They use household appliances, it's just a very impressive set up and they are a very intelligent couple, I have lost hours just chatting with him. One night having this very conversation about batteries and solar we finally decided we better head in for the night at midnight, he is a captivating speaker.

If you go with the L-16s make sure the floor will support them, I've seen a couple rigs that had breakage from too much weight in too small a spot. Adding an under-floor support ahead of time is a lot cheaper!