What I'm making is a 12 cell Li-Fe battery charger for e-bike applications. A commercial charger capable of charging these at 15A would be quite expensive. So, I'm just going to do a CC charge until they hit 3.6v/cell and then the charge will terminate. These batteries don't take much charge during the normal CV stage anyway, so I'm not too concerned about getting every last mAh out of them.
I plan to use a 50v DC supply. Worst case, the batteries are at around 2.9v/cell, which is 34.8v. The transistors will have to bleed off around 14v. At 15A, that's quite a bit of heat at around 200w. But, I won't be filtering the supply so it'll be getting 15A pulses so that should help the heat somewhat. Plus, the cell voltage will rise fairly quickly reducing the differential voltage, so that 200w will go down to less than 100w pretty fast. Towards the end of the charge, the tranistors will be dissipating less than 80w. Yeah, that's still high, but my goal is circuit simplity over efficiency. This charger will be stationary in the garage, so size (for proper heatsinking and fan cooling) is not a concern. Besides, I have just about all the components I need right now in my parts bins.