kfong wrote:Update, looking for a suitable inductor. The one I found, I wasn't happy with the wire gauge, so I looked around and found a ferrite toroid, and started wrapping wire around it. I ran out of wire, but felt it would be good enough for the test. Worked better than I expected. It just goes in between the battery and the speed controller. No bms shutting down from the capacitive discharge coming back from the controller.
Like some other people in this thread I had problems that the DeWalt BMS would cut when connecting to my controller. The current peak to charge the controller input caps was too high. I started winding an inductor (had bought the toroid from Kin just in case). Then it occurred to me why not use an NTC resistor as inrush current limiter of the type used on many switched power supplies. I had used these on the input side of my own controller project (http://endless-sphere.com/forums/viewtopic.php?f=7&t=19993&start=15#p292906
) just for this purpose (They are the two black discs in the bottom left corner of the PCB from the previous link), but commercial controller manufacturers seem to not be so careful.
Here how it looks on a kfong board. Note the much smaller footprint of the NTC resistor compared to the inductor.
The NTC I used is rated for 15A. Gets warm (as it is supposed to do) running near the rated current. Tried it both with the controller from the cellman 350W geared kit and a crystallyte 20A. Works great to prevent startup BMS tripping (and sparks on connecting the wires) for both.
I was looking to try this on some higher amp controllers, but had a hard time finding a suitable part number on digikey. Instead I was thinking of using higher ohm, but low current NTC for startup only, like this one:http://parts.digikey.com/1/parts/1521264-cur-limiter-inrush-50-ohm-1-6a-sl10-50002.html
Then when caps are charged just short the NTC out of the circuit. I'm curious if you think this would work on the Castle HV160? The HV160 does some "motor twiddles" on bootup that are probably pretty high current. Can those be turned off in the programming somewhere? Or the NTC has to survive that?
Mike B wrote:
Question, will the interface allow regenerative charging? Lots of hill here, up and down. The 4011 motor on a previous bike would hit 20 amps of regen going downhill (had two Watts Up meters wired head to head to read this once I figured out why the one meter's voltage was going high on downhills). But your board has a diode. So I think not....
I run w/o the diode. I haven't purposively used regen, but my 9C often puts 100-200W backwards when backing off the throttle, and the DeWalts seem to survive that.
Another "feature" (not sure if accidental or not) is that on a 2s pack, when the BMS triggers at the end of capacity of one it seems to allow current though, so I can keep riding on half the voltage on the remaining pack without any reconfiguration. B.t.w. I get about 2Ah of the rated 2.3Ah from my 2007 toolking 24V packs.