Self-built Lifepo4 load tester with potential for very high power

[Zjohn]

Don't know if this is appropriate here because it probably isn't an electronics forum, but given that many people seem to purchase low-power and not very high quality load testers I thought I'd share my thought on building a potentially very high *constant current* load tester - making capacity measuring easy. The design as I post it here should work from about 3S to 8S based based on the opamp; with a rail-to-rail opamp also down to 1S and with some mods on opamp and FETs also to much higher voltages. With sufficient cooling for the FETs (ok, no mean feat!) it should be good to just about any load current. Build it for low power with just 1 FET so far and am looking for comments and improvements.