[ricket]

5C is still like 10-15min for a full charge -- and definitely does have side effects, it causes damage to the battery and will result in sagging voltages and lower capacity in just tens of charges. 5C is too high of a charge rate.

I feel like you've mixed up LiFePO4 and LiPo. LiFe has low charge rates, lower energy density, lower voltage, and higher cost compared to LiPo. For R/C aircraft, it's typically used only for the receiver and servos of the really large helis/planes, because its lower voltage is tolerated by the servos whereas a LiPo needs a regulator to step down to 5-6V for driving servos. I can't speak for expensive hand tools, but "everyone" in the R/C community uses LiPo.

[codeduck]

No. There are various types of LiFePO4 - some are as you say used for receivers etc but the ones I am specifically referencing (and perhaps should have been more explicit about) are the A123 systems Lithium Iron Nanophosphate batteries, which are capable of 60C burst discharges and 5C charging rates. These are definitely used as primary power-packs for flight - I flew with people who were using them when they first came out.

[ricket]

Sorry. I googled to check before posting too, but didn't consider specifically the A123. It still looks like it is an uncommon choice for main battery pack but I can see how it's at least feasible (I probably wouldn't go for the tradeoff personally).