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Advice on Solar charger

Ironman

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Nov 29, 2020
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Somebody set up my offgrid friend with bunch of AGM batteries and a 280 watts of solar panel.
He has 1700AH of 12 volt AGM batteries in parallel, divided into 2 banks. All are 12 Volt and that is also his inverter input. He has borrowed my 150 amp charger, and is using a gas gen to recharge. He knows nothing about electricity except that 12 volt won't shock you.
He has recently purchased 4 Canadian Solar 450 watt panels, I told him it was a great improvement over the crap he had. I also told him to get a proper solar charger and recommended a Epver Solar Charger that will handle 40 amp at 12/24 volt. I will hook up 2S 2P.
This is the one https://www.ebay.ca/itm/393236672794?_trkparms=aid=111001&algo=REC.SEED&ao=1&asc=20180816085401&meid=68494effcc704026ac555cfc3d8d2111&pid=100970&rk=5&rkt=8&sd=372467921248&itm=393236672794&pmt=1&noa=1&pg=2380057&brand=Epever&_trksid=p2380057.c100970.m5481&_trkparms=pageci:9768b558-d1cb-11eb-8af5-327b87fe3a1d|parentrq:299cf9df17a0ab84680ef0c9fffc300a|iid:1
I am having second thoughts because it may be too small. Will recommended it on a video, but it may not handle 1800 watts input. Any ideas or suggestions will be appreciated.

One of these days I want to get him to bump up to 24 volts with his battery pack, but I have to go one step at a time. He is on a small pension and has little money.
 
That is really, really too much battery for 12V. Forget about going to 24V, go straight to 48V. Can you please be a bit more specific about what each battery is? What is the Ah of one single 12V battery?

I'm assuming that wired in series for 48V, the same batteries will be ~425Ah. That was about the capacity of my first 48V bank. The advantage of the higher voltage will be lower amperage going through the wires. Realistically, you want at least 1/10C for good charge density. With 1700Ah, that's 170A or better.

Re-wire them to 48V and that's 43A instead of 170A. You'll need a far cheaper controller for that. I would forget the Epever 40A. Take a look at Epever's better model, starting with the Tracer 5415AN. At 48V you'll need 425Ah X 1/10C X 50V charging X 1.18 Fudgefactor = 2507W of panels

Can he get more of those Canadian Solar panels? He'd be better off with 6 of them instead of 4, though with 4 you could scrape by. AGM's usually tolerate a higher charge density then regular lead-acids, up to about 1/5th C.
 
First, thank you for replying, Michael.
I am leading him slowly as he can afford it, towards this goal. 48 volt is the way to go and has so much more in it's favor. This will mean a new true sine inverter or an all in one, plus a 48x12 volt DC supply for his 12 volt CPAP. I have funded him for the panel purchase, and when that $1200is paid back, we will discuss cutting down the battery bank to something reasonable. I am 1000 miles north of him now and I called and he told me these are Powersafe SPS 190F 12volt at 190 AH The banks are 7 batteries each paralleled for 1330 AH per bank.
I can get more of those panels in the future, but they have to come from china. For some reason high watt cells are not sold in N.A.
 
First, thank you for replying, Michael.
I am leading him slowly as he can afford it, towards this goal. 48 volt is the way to go and has so much more in it's favor.This will mean a new true sine inverter or an all in one, plus a 48x12 volt DC supply for his 12 volt CPAP. I have funded him for the panel purchase, and when that $1200is paid back, we will discuss cutting down the battery bank to something reasonable. I am 1000 miles north of him now and I called and he told me these are Powersafe SPS 190F 12volt at 190 AH The banks are 7 batteries each paralleled for 1330 AH per bank.
I can get more of those panels in the future, but they have to come from china. For some reason high watt cells are not sold in N.A.
 
Yes, I can see how you don't want to screw around with the operation of CPAP.

Is there a chance he can sell off some of the extra batteries to get some cash to finance the rest of his purchases? Even three strings of four batteries each would leave him with two extra batteries.

I suppose you could help him create either two of three strings of four batteries in series to get 48V. I'm not a fan of parallel strings, but you have to work with what you've got.

The good news is that a 48Vto12V converter is cheap, and can be spliced into the system without much fuss.

Assuming you create three strings, then the amount of panel you'd need is...
190Ah X 3 battery strings X 0.125C X 50Vcharging X 1.18fudgefactor = 4200W

Will he need a battery that big? Maybe two strings is all he needs...
190Ah X 2 battery strings X 0.125C X 50Vcharging X 1.18fudgefactor = 2800W

Going with a bottom rate of 1/20th C, two strings would get by with....
190Ah X 2battery strings X 0.05C X 50Vcharging X 1.18fudgefactor = 1120W
He'll have to keep a close eye on battery voltage to make sure he doesn't dip bellow 50% capacity with this low charging rate. I personally would never go with that low a charging rate, but if he's really conservative, his banks might stay charged.
 
Well, his usage is pretty light, but it seems to be the best solution at this moment, is to reduce the battery to 3 or 4 in parallel.
He uses LED lights, CPAP, and sometimes a movie on his little TV.
He may want to sell some batteries, but for what he paid for these, he could never buy them again.
 
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