Maast
Compulsive Tinkerer
I've been buying BIG lifepo4 cells from 5 different vendors on Alibaba in the 260-280AH size, each one weighs 12 pounds. I've taken a nasty hit on shipping by buying just one cell from each vendor but since I intend on buying another 48 of them I thought it worth the investment to get and exhaustively test them before going on with a large order. Each cell has averaged about $125 and shipping has been around $85.
Initially I intend on replacing my aging existing 350AH 48V AGM whole house backup bank and then I might get into the battery business. I've got some thoughts on producing 12V modules with integrated thermal heating/cooling via onboard peltier modules. Or maybe just resell these large cells.
At any rate - to test the cells I've rigged up a 500 amp load bank called a liquid rheostat, it's a ring of sheet metal inside another ring of metal separated by about 3/4 of an inch inside a 30 gallon tank of conductive sodium carbonate (washing soda) solution. The inner ring can be raised or lowered to vary the resistance and control how many amps I want to draw.
I'm still working on automating the test rig, I can manually run it through the 300A shunt w/ AH counter and that works pretty well but I'm assembling a automatic low voltage disconnect from a adjustable lipo low voltage alarm, a relay board and a 400amp normally closed contactor from electriccarparts. That way I can at least start a test cycle and step away from it for a few mins an not have to worry about over discharging.
I want to automate charge/discharge cycle testing w/ data logging using an arduino but thats proving to be a heavy slog.
Thought somebody else might find it interesting.
Initially I intend on replacing my aging existing 350AH 48V AGM whole house backup bank and then I might get into the battery business. I've got some thoughts on producing 12V modules with integrated thermal heating/cooling via onboard peltier modules. Or maybe just resell these large cells.
At any rate - to test the cells I've rigged up a 500 amp load bank called a liquid rheostat, it's a ring of sheet metal inside another ring of metal separated by about 3/4 of an inch inside a 30 gallon tank of conductive sodium carbonate (washing soda) solution. The inner ring can be raised or lowered to vary the resistance and control how many amps I want to draw.
I'm still working on automating the test rig, I can manually run it through the 300A shunt w/ AH counter and that works pretty well but I'm assembling a automatic low voltage disconnect from a adjustable lipo low voltage alarm, a relay board and a 400amp normally closed contactor from electriccarparts. That way I can at least start a test cycle and step away from it for a few mins an not have to worry about over discharging.
I want to automate charge/discharge cycle testing w/ data logging using an arduino but thats proving to be a heavy slog.
Thought somebody else might find it interesting.
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