Hi all,

I plan on using some caps in a PWM motor driver circuit. The purpose of
the caps is to turn the current pulses of the pwm into a smooth average
current for the battery, so that the wire and battery internal resistance
does not have the additional loss of the high current pulses. However,
this means that the caps will have to handle a very high ripple current
(in the 20 amp range). I've found excellent low impedance capacitors, but
the ripple current spec is low in all cases I've seen so far, around 3
amps.

What are you supposed to do if you need a higher ripple current rating? I
can't afford the weight of having 7 of these in parallel. However, I can
stand to have a reduced operating life (they are rated 5000 hours and 500
hours would be acceptible). Is there a derating relationship between
operating life and ripple current? I saw such a chart in one datasheet
but not in this one. I'm looking at the Panasonic FC series
(specifically digikey part number p10335)

I don't think tantalum is an option because I need high capacitance (2200uF).

Thanks!

Sean

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