Automotive relay, 3 resistive wire from an old air dryer, and 2 small switches
Some welding
Resistors and switches close up
and the final product
There is an input for a 12V power supply, I used a solar charged 12V battery for that
There is an input for a 12V power supply, I used a solar charged 12V battery for that
Now some testing with remaining LiFePO4 cells
Power switch ON
View from the top
From the left side
From the right side
I later on added a little piece of aluminum to dissipate the heat a little bit more
The resistors are going up to 75°C and more or less 4A are going through them :
Measured Resistance: 0.8Ohms
Current: I = U / R = 3.2 / 0.8 = 4 Amps
It works fine and I drained one cell yesterday with it, in 2 hours I think
The total cost is close to 60 USD:
Programmable dual relay voltmeter 47.50
Automotive relay 12V / 30A 3
Red flashing LED 5
Switches (x2) 2
Resistive wires free
Wires and connections 3
Battery Clamps free
Japanese fishcake board free
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Total 60.5 USD
That is a nice little setup for discharging single cells but really only useful for final trimming once most of the energy has been removed. I use a 9" DC motor to drain full cells fast then use my PowerLab 8 to trim them to the final voltage. But I do like the design for those that don't have a PowerLab 8 to trim the cells. Kudos on that one. Clean and small.
ReplyDeleteThank you for your comment.
DeleteYes, I usually connect the cells in series, then bleed them with the DIY ESS Grid Tie Inverters (like you do with your Motor), while watching their voltage; When they are close to 3V, I stop, and then use my Bottom Balancer on each cell, and draining 4A, the job is done pretty rapidly after that :-)
What are the two voltage thresholds you use to enable and disable the relay?
ReplyDelete2.44 & 2.71
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