DIY Offgrid Project – Integration Part 1

I have been busy over the last few weekends and the weather has been unappealing for climbing around the roof when I have had time so I still don’t have an solar panels installed but all the parts of this system have been cluttering up the house so I decided to mount things on the wall and test out strapping the battery cells together this afternoon.

The straps came in a set of four at Bunnings and the timber end plates are some leftover Ikea solid timber bench. The best advice for LiFePO4 cells is that they should be strapped together because the cells bulge when they are full charged due to the lithium ions that are deposited within the graphite coating of the cathode during charging.

The two solar isolators are overly optimistic Chinese switches that claim they are rated at 32 amps. I’m doing 10 amps per contact so we should be good. The DC breaker is rated for 600 volts DC and 125 amps which is the absolute maximum the inverter is rated for. I hope I can find another enclosure the same for my second inverter. I bought this one when I made the 20 amp Tesla charging adaptor. IMG_0936

The cells will be tied together with these intercell links. They are 25mm by 3mm so they have a 75mm² cross section. That’s equivalent to 50mm² of coper which can handle around 150 amps with a recommended breaker of 125 amps. That’s around the maximum continuous rating of the cells anyway.

IMG_0917

The white tube on top of the cells is Alvania electrical junction grease designed for aluminium connections. You can buy it here. This will all make sense when I join everything up and integrate the Battery Management System.

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