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rugercpl
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# Posted: 23 Jul 2014 22:24
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I just bought a solar package containing (3) 100ah batteries, and (2) 150 watt panels with a charge controller, and 1500 watt inverter. It's working very nicely to power my whole 3-season cabin. I was hoping somebody could give a guesstimate as to how much recharging capability this has...say if the batteries are depleted by 2/3rds...how many days of sun would it take to fully recharge. I'm getting full sun on the panels from 10:30 to 5:00 roughly when it's sunny. I bought a battery charger to recharge from my eu2000 whenever I need it.
Another guesstimate....how long might it take to fully recharge the batteries from just the eu2000? Let's say if the batteries were depleted by 2/3rds?
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creeky
Member
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# Posted: 24 Jul 2014 08:34
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Lol. Okay. One. You shouldn't use 70% of your battery unless you plan to replace every one to three years.
But, say 50%. you have 300 amp hrs I'm going to guess at 12v, so 2 kw at 50%. Your 300 watts solar times 6.5 hrs means you should be able to fully recharge daily.
Of course your charging will only be 80% efficient, so it might take a bit longer. (With that size battery pack you might want to use a little less power. Say more in the 1-1.5 kw range.)
What size battery charger did you buy. A basic rule of thumb is your charger should be 10% of your amp hr capacity. So I'm guessing you bought a 30 amp charger. That would recharge your batteries in about 5 hrs.
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rugercpl
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# Posted: 24 Jul 2014 10:43
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Thx for that. Yes to a 30 amp charger and my bad running my batteries down that low....it was sort of a trial run to see what my "average cabin use" does to the batteries without using the generator/charger to maintain a full(er) charge. Im going to be adding batteries and more panels as I can afford them.
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creeky
Member
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# Posted: 24 Jul 2014 14:55
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rugercpl you have a pretty good system the way it is. you've got 1 to 1 amps storage to watts on solar. 10a to 1a on the genny/charger. man. that is the perfect small system. congrats.
there's a chart for lead acid batteries. you want them to last 20 years. keep them on float and never use them. most people shoot for 8 years at 20% discharge/3000 cycles. Once you get to 80% dod your batteries are only likely to get 300 cycles. If you have pretty good batteries you can get like 1000, or top of the line, 1500 cycles.
i don't know how often you get to the cabin, but at 70% 500-1000 cycles for you could be years. and then you can buy better, not lead acid, storage tech.
and anybody buying a bigger solar system, do look for lithium iron phosphate. money well spent.
can't wait till I can say, hey, here's a small lfp battery pack with bms ... but those acronyms will have to wait for another day.
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creeky
Member
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# Posted: 24 Jul 2014 15:04
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oh. and this is something I don't really have a handle on.
but: for the sake of exploration
if you get 1000 cycles at 80% dod. and 3000 cycles at 20%. Surely 1 cycle at 80% isn't going to have much effect.
I've seen some posts where guys talk about "lazy" battery packs. Where the dod has been fairly low for years. 10-20% dod. i have read recommendations for a couple of deeper discharges followed by recharging to wake the batteries up.
so your batteries have been on a shelf, at 70% dod you're kickin' em in the butt and sayin', get to work. good idea no?
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rugercpl
Member
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# Posted: 24 Jul 2014 17:01
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Im going with that. That makes me feel better thx !
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ILFE
Member
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# Posted: 26 Jul 2014 14:15
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rugercpl,
I live in SE Asia, where - for about half the year, we get so much rain that we begin to wish we were born ducks. (I'm growing feathers as I type this, in fact.)
Anyway, I had a similar set up at our off-grid farm - 300 watts, 240AH, 12vdc. I purchased a fourth 100 watts panel.
Of course, in my case, I rely completely on solar at the farm. We have no generator, no mains, no nothing. The array provides 100% of our power needs at the farm.
So, my advice, I imagine your controller is sized for it, would be to add another panel to your array, first. (I noted your comment about adding more batteries and panels as you could afford them.) I imagine that would make a lot of difference and less run time for your generator.
It's just that, with the losses in your system (typical of all systems), you should be putting more into your batteries during the day, by way of your panels, than you currently are. (If I am thinking clearly enough at 01:14) 450 watts of panels should give your batteries time to bulk up, absorb, and float before the sun goes down.
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rugercpl
Member
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# Posted: 26 Jul 2014 14:37
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I completely agree thx...I'm going to add 2 more panels and a 4th battery and I think I'll be "made in the shade" 
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creeky
Member
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# Posted: 27 Jul 2014 11:50
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I'll second ILFE. I'm up to 1.5 watts solar to 1 amp battery, because we have two-three months of heavy cloud cover in my area (sadly bringing snow not rain).
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LastOutlaw
Member
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# Posted: 13 Aug 2014 19:58
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Uggggghhh....in my case I need a 60 amp charger. $400 or more.
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Jafo
Member
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# Posted: 13 Aug 2014 20:58
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I have 2 115 amp hour batteries, 3 panels that could produce a max of 245 watts of power with my MPPT controller. As long as I have sun, I can't kill the system with powering lights, small tools, radios, etc.. Much of this will depend on what it is you're powering with your system too.
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