Good day everyone. 

I'm an electrician with some good knowledge of industrial UPS installations but alas, the sheer volume of different consumer products on the market has me stumpoed a little. 

What I'm looking to do is run a remote shop completely offgrid. Loads will be as follows. Daytime load : 3A 

Nightime would be around 1.5A. So give or take about 350W. 

My plan is to power these complete from solar and batteries. I'm considering a 48V Lithium system but cost is rahter prohibitive (as far as I understand these batteries can do 80% Dod safely)

So far I settled on four 12V 200Ah (2s2p)(so 24V 400Ah) batteries. From my calculations I would draw about 1.5A at night so for a 12 hour darkness I would not be pushing these batteries past 50% dod. During the day the solar can charge them up again (lets state about 8 hours of good sunlight). 

Can I draw on your knowledge as to what is best practises and what to avoid. 

 

Granted, checking the prices now again, a 48V 4.8kW Lithium pack might not be so much worse. 

My thinking is to install a Sunsynk 5kVA. Not that I will ever need that much, but the mppt charger seems to be specced decently in order for daylight to charge up the battery fully with enough panels

My  1cent.  Avoid leadacid/VLA/GEL type batteries. Lithium cheaper in the long run and charges quicker. 

If I do the sums correctly, you would get to around 12kWh a day. Is 3A the average? IE it could get quite a bit higher at times because of (EG) water heating? 

It's important to consider these peaks as well as the average. Batteries with the same capacity might have different allowable maximum discharge current. 

And if you want to go completely off grid, you need to overdo everything so that you'll get through an overcast day or two. A hybrid solution (can use solar, battery & grid) may be more cost effective 

Edited March 30, 20231 yr by Bobster.

My brother got 2 years out of his 200ah “solar” batteries which was lightly used.

R25k wasted.

Too many negatives to mention.

Totally not worth it. 
He is on two 5kw lifepo4 batteries now.