RCM Lipo impressions

[BrianG]

Yeah, the drop is quite a bit different, but also the amount of mAh taken out of equal capacity packs @ 3.5v/cell is huge too. Tells me the discharge curve is far flatter for more of the charge.

Eventually, I'd like to build a 100A+ constant current device to test the higher currents, but dang, the transistors and power resistor setup is kinda big. 10A takes two 2N3055 transistors, with an NPN darlington transistor driving both bases to keep the current gain high (prevents loading, and resulting v drop, of the regulator that drives everything). 100A would take 20 of those transistors, not to mention the fans and heatsink! 100A @ 18.5v is 1850w... that's a LOT of heat!

I'd like to use FETs, but not sure how to drive them in linear mode as well. They would definitely be much easier to parallel (no current-hogging due to negative temp coefficient) than transistors...

[JThiessen]

Originally Posted by BrianG

Yeah, the drop is quite a bit different, but also the amount of mAh taken out of equal capacity packs @ 3.5v/cell is huge too. Tells me the discharge curve is far flatter for more of the charge.

Eventually, I'd like to build a 100A+ constant current device to test the higher currents, but dang, the transistors and power resistor setup is kinda big. 10A takes two 2N3055 transistors, with an NPN darlington transistor driving both bases to keep the current gain high (prevents loading, and resulting v drop, of the regulator that drives everything). 100A would take 20 of those transistors, not to mention the fans and heatsink! 100A @ 18.5v is 1850w... that's a LOT of heat!

I'd like to use FETs, but not sure how to drive them in linear mode as well. They would definitely be much easier to parallel (no current-hogging due to negative temp coefficient) than transistors...

Couldnt you get an old audio amplifier and make something from that? I just threw one away that had been in my garage for some time. Wouldv'e paid that forward to ya.