Beginning a Shed build, 240v 48v SLA, would love advice on inverter/battery balancer

broombroom

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Joined
Jul 11, 2021
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Hi Everyone, I've been dreaming and scheming of ways to minimise my carbon footprint for a long time and finally am in a position to start making a solar setup to begin to change that.
Thanks in advance of any advice you have.

The plan is to learn by building an off grid battery system in my shed that will supply power to a freezer, a fridge and perhaps down the line, a washing machine and dishwasher. They are all being currently run on grid, and the idea is to experiment with taking parts of my power consumption off grid as I learn, by running extension cords from the shed to individual appliances.

I am one of the many people who got sucked in on telecom UPS batteries, I have bought 20 ex mine site UPS style batteries 12v 100Ah for $500, so it works out to be $25 a battery. After doing more research I have realised their cycle life isn't going to be what I hoped for. Nevertheless I am going to push ahead and build the power setup with the aim of replacing the battery when these ones die. That way I will have learnt from these batteries and gotten some use out of them.

The plan is to wire them up 4 in series to get 48v and 5 parallel strings, so 4S 5P. I'm still calculating the cable size needed to carry all the amps, and waiting on bolts to arrive for the battery terminals, so still plenty of planning to do.

I am hoping to use a MPPT/Inverter combo like the Growatt SPF 5000ES as it seems to minimize wiring and I like the fact it has wifi capabilities for monitoring.

My questions are:

1: With such a big battery bank in parallel, is there any advice on battery balancer or a BMS type thing for lead Acid batteries? to try and keep the bank in good health?

2: some advice I've received is to get a seperate MPPT and inverter so that adding on or replacing parts is easier in the future. This seems counter intuitive, surely getting an all in one is simpler and easier? would love to hear other peoples thoughts and experiences.

3: Any advice or recommendations on good 48v pure sine wave inverter with wifi monitoring would be invaluable.


Thanks for your time!
 

MisterSandals

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Joined
Nov 5, 2019
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Location
Silicon Valley
I'm still calculating the cable size needed to carry all the amps,
If you know your max momentary load (likely your inverter size, in watts), and wire length its easy with this tool (change wire gauge until below 3%):
 
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