acceptance charging rate AGM batteries

Oh my. Last night at 0300 it was 78F. Mid nineties to 100, 3-6PM. With the ocean being 3/4 mile away this is not a dry air clime. I believe a few years ago I clearly stated when electrolyte was made inaccessible it vastly complicated the art of determining true state of charge. Things have not changed. VRB have an elevated voltage profile and do not bell-curve as profoundly as a flooded high antimony battery. There isn't a simple way or work-around. Construction and age variances plus capacity depletion would shatter a crystal ball.

i'm not going up to the 1500w mark
but by replacing some (2-3) more of the unisolar, with 100w poly panels
probably from windy nation
i can get above the 800w mark

the max i have seen in output from 40amp controller is 31amps
this summer i pulled new ( '00' ) charge cable from the controller to the new AGM batteries
i move too much to make tilting panels to be practical, unless its an automated system
so increasing the total wattage is the most effective use of the $$ investment in this project

some new taller mounting feet/brackets, to get some roof clearance would aid in cooling and increasing the output in HOT weather

Hi Mr Wizard,

My existing system, from May to mid October, if weather is cool, I run out of fresh water before I run out of power, so long as I run the fridge on propane. My only reason to do a massive upgrade would be to run the roof air.

Come November and I must either travel south, or be in a location where I have 45 amps (3 x 15, or a 30 plus 15, or 50 amp) power source, because I do not enjoy running the propane furnace. Small towns have no way for me to fill the propane tank, so I heat 100% electrically.

Even if I did the 1500 watt upgrade--I could still not heat electrically. It would delay me moving to an RV park by a couple of weeks.

I burn more propane running the fridge than for any other reason.

you can double wattage in the existing USED roof space using 12v poly panels
for not too much cost, if you have some unused space, you could maybe triple your wattage

i know if i wanted to run the roof air from solar, i would need at least 1500w
i budget for the gas to be used in the summer months

my brothers place is almost 2500 miles away, and no lake, for that i have to camp at the nearby state park

today its 90+ here and there

but i am considering, increasing my solar, and hopefully save more 'fuel' $$
but right now since I need to spend $$ to run the genny to stay cool,
i let it charge up the batteries too

Hi Mr Wizard,

For everything except air conditioner use, 12 volt solar is quite adequate. Once you look at the wattage needed for roof air, it becomes clear that 48 is a winner, and 24 is barely viable.

Yes, I could replace the existing panels--but I'm limited by the Blue Sky 3024 di. In MPPT mode it doesn't "do" 30 amps.

What solar I do have appears to "out perform", and works in both leafy shade and rain.

I could stick with 12 volts and not replace the Magnum inverter charger, but unshaded space on the roof would not allow me to do much more wattage than I currently have. So I'd still be having an aluminum frame work added. I suspect that would cost as much as the new solar system--and goodness knows if it would be wise.

My cousin is a talented man, and has the equipment to weld aluminum, but, he is a perfectionist and will not do so.

If I intended to full time for another ten years--I'd be close to break even on costs. But more likely I'll go back to part time in 2019 or 2020.

My RV is only 2 inches under the legal limit for width, so hanging panels off the sides is not viable either.

Much as I hate the generator, I have it, and it is paid for. So I fear my choices, for hot days, are to be a "power pole princess" or a "gas guzzler generator head".

Today I'm a member of the PPP as the ambient temperatures is 89 f (31.6 c).

It is fun to dream.

MrWizard wrote:
Don
You could replace the unisolar panels with one of higher wattage
And parallel another controller if needed
I'm sure some body would but those unisolars from you

I already replaced two of mine last summer 2015,
And I'm considering replacing the rest of them

While 24v or 48v is in some ways appealing
I don't find it necessary in an RV

Don
You could replace the unisolar panels with one of higher wattage
And parallel another controller if needed
I'm sure some body would but those unisolars from you

I already replaced two of mine last summer 2015,
And I'm considering replacing the rest of them

While 24v or 48v is in some ways appealing
I don't find it necessary in an RV

Hi Mex,

Alas, I do not have an amp-hour counter. The only one I truly trust is the smartgauge and since I have 2 banks, I would need two of them. I'm resistant to the use of a shunt since I "push" the system HARD, often over 150 amps DC for load support. Cost is beyond the budget. Even with that level of sophistication, readings would have to be taken without the solar system. I think the hybrid load sharing feature of the Magnum would have to be turned off as well.

I've reached the end of my electrical system development except for advanced surge protection.

The mistakes I've made would be costly to mitigate and are not really of much consequence. They are:

1. not having a larger capacity charge controller to allow for expansion of the solar panel harvest.

2. not moving to 48 (or at least 24) volts for the battery bank.

If I wished to "fix" these issues I would have to replace the rather wonderful Magnum inverter charger, and replace the charge controller, while adding a dc to dc converter. To boost solar, I'd have to add a rack that covered the entire roof of the RV and replace the existing heat and shade tolerant panels with a heck of a lot more wattage. A thousand dollars per month for a year would get me there, but on a beer budget it just is not going to happen.

Following that path puts me out on a limb and removes the redundancy that is "built in" to the existing system. At the moment, should the Magnum fail or "dislike" a GFCI outlet, the PD 40 amp converter can simply be plugged in.

I do carry a back up psw inverter in the 1000 watt class.

Very astute Don. Do ypur own trends and tendencies graph using an amp hour meter. Make it like a mileage distancd chart. Algebra. If this is this and that is that the 3rd factor therefore, must be...

red31,

The flooded starts to taper first and at about 85% state of charge acceptance rate is about 12.5 amps per one hundred amp-hours of storage.

PT

Let's say you charge a 100ah AGM and flooded both @ 12.5A
Which one hits its set pt first and begins to taper first?