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Solar set up battery voltage


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Just wanting to bounce something of you guys and gals. I currently have solar set up with 4x250w panels, a 150/85 Victron MPPT, a Cotek 2000w 48V inverter and 8x 105ah 12v batteries connected in series/parallel to give 48v banks. 

My Cotek inverter has been giving me issues and this is where I've been thinking. 

A family member has a 24v inverter. I have also been looking online and there are some good reviews for a 24v Chinese inverter. Yes, yes, I know but budget is tight and I was thinking of having it as a back up to the family member's one. 

This is where my layman thinking needs some wise brains to bounce this off. I realise 48v system is better in most instances as it allows for smaller cable sizes. The charge controller can also be a lower amp one. The latter is not an issue with my small system as 85amps is fine. When it comes to cables, the battery bank, inverter (whichever it ends up being) and charge controller are all within 1m of one another. The only thing that is distance are the panels with cable length of under 10m.

Would I need to increase my cable sizes if I decrease voltage? What potential issues do you see if I change my battery bank to 24v from 48v? My current daily power usage is under 4kw/h. I realise I may run into issue of I want to increase panels one day. True? I have read that too many parallel banks are not suggested. I'd be looking at 4 parallels of 2x 12v batteries then connected in series. Will my battery efficiency be affected? I already run to 40% DOD so don't want to be running the batteries lower if this is somehow effected? 

Thanks in advance. 



Edited by ClintZA
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24V will be fine if you stay under <3000W. The big thing is the cable sizes that need to handle the current. For the same power (W) you will double the current when you half the voltage. The cost of the cables and difficulty working with such think wires is why you would want to move to 48V with a system >2000W. 
We are talking about the cables between your MPPT and battery, and battery to inverter. You PV cables is not influenced.

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