John in CR
100 TW
My thinking is that with different C rate packs paralleled at the ends the voltage stays the same. Under short high load more current will flow through the lower IR higher C rate portion. When I let off the throttle a slight voltage differential from the different SOC will send energy from the lower C rate portion, but the voltage difference should be low enough to keep these cross pack currents from getting high. Sure it will be a bit more stressful than an homogeneous high C rate pack, but as long as I avoid deep discharges the effect shouldn't be too significant.
This view is supported by my experience over the last year and a half with a 30s pack. 20s was homogenous and charged with one charger. The other 10s was a mixed bag totaling a slightly higher capacity, and charged with a separate charger. That 10s included some 20C 18650's I was testing, along with some older 20C hard packs and 45-90C nanotechs. I very rarely went past 50% DOD, and over that period all of the sub packs remained in such good balance that I never had to balance charge any of them.
This view is supported by my experience over the last year and a half with a 30s pack. 20s was homogenous and charged with one charger. The other 10s was a mixed bag totaling a slightly higher capacity, and charged with a separate charger. That 10s included some 20C 18650's I was testing, along with some older 20C hard packs and 45-90C nanotechs. I very rarely went past 50% DOD, and over that period all of the sub packs remained in such good balance that I never had to balance charge any of them.