Vas has already stated that he tested these at 100% PWM and with his latest resistor layout no heatsinks were required. I can’t think why you’d need so much cooling? The balance resistors are only used at the top
of the charging cycle. Even if the cells are poorly matched the balance current required should be related to your charging rate, ie you drop the charging current as the cells are top balancing. I’ve seen my cells at well over 30 degrees ambient and still no need for additional cooling. After the cells have been balanced once you shouldn’t get a large drift between cell SOC so you only need large balance currents when the cells are new and you can get around that by charging more slowly for longer at high SOC then change your BMS and MPPT settings when the cells have completed a balance cycle a couple of times. With LifePO4
there is only a very small change in SOC where you would be balancing so charging with more current is fairly pointless, ie you’ll find at the top of the charge curve there is a rapid change in voltage for little change in SOC, that’s where you’ll be balancing the cells.
Also in his design you can see the cell vent which may be quite useful.
One of the original design goals of these modules was to reduce the twisted cable lengths so communication shouldn’t be an issue even in large packs. Perhaps you could use a tool for the JST connectors? I agree they are a fiddle.