John in CR said:
I've got 24 A123 cells patiently waiting. In what way are these licos better? 2P is over 4ah and is capable of 140A continuous, not to mention they will last for years and are safe enough to put in Joe the Plumber's cordless tools.
John
These are every bit as good, in my opinion, and a ton safer. On a bike, a few ounces more in weight is nothing. I even switched over to use a123s in all my RC helis. I got tired of having to worry about charging, punctured packs from crashes, etc. Many others have done the same.
RC packs are smaller and lighter, especially for fairly small capacities, like under 10Ah. If you want a setup that is going to give you some commuting range, for instance, now you've got to have a messy and comlicated wiring harness that will connect multiple 5Ah packs in parallel and in series. How then to charge them? RC chargers, with built-in balancers do a great job of balance charging the packs, but you can't have one charger that will do your whole setup.
Most RC setups are based around using packs that are multiples of up to 6s. It is not as easy to map LiPo's nominal 3.7V into existing 24V, 36V and/or 48V SLA setups, which would increase the charging options significantly. Actually, a 10s LiPo pack, with a nominal voltage of 37V and a CC/CV cutoff of 42V comes closer to a 36V SLA configuration, but even there most 36V SLA chargers have cutoffs of 44-45V, which is too much for a 10s LiPo pack. If you were trying to match LiPos to use in a typical 48V setup, which has a CC/CV cutoff of around 58-59V, you really need to use a 14s LiPo configuration. Using two 6s LiPo packs is only around 44V nominal, whereas with a 14s setup the nominal voltage is about 51V.
So, let's say you are going for a setup that requires at least 10Ah of capacity, and you want to charge the whole setup with a single charger, in a reasonable amount of time. Using typical RC packs you'd need to use three packs in series, to get to 14s, and then since the max capacity typically available in RC packs is 5Ah, you'd need to have two in parallel to get 10Ah. That's six packs, and a mess of wires.
The nice thing about LiFePO4 cells, including a123s, is that they map well into existing SLA setups. For charging purposes, 4 LiFePO4s equals 6 SLA cells. Makes it easy to configure packs that can make use of the many existing SLA chargers out there. You get the added benefit of higher nominal voltages. A typical SLA cell has a CC/CV charge cutoff of around 2.40-2.45V, but this very quickly drops to about 2.0V per cell. An 18 cell SLA will get charged to about 44V, but its nominal voltage will be 36V. A 12s LiFePO4 packs will also get charged to 44-45V, but its nominal voltage is 3.3V x 12, or about 40V. You get an "extra" 4V. This is one of the reasons why som many are so pleasantly surprised when they switch from SLAs to a LiFePO4-based pack. Many assume that it is simply because LiFePO4s have less voltage sag, under load, which is part of it, but they are starting out with more voltage from the get go. One of the common mistakes I've seen manufacturers make when trying to match other Lithium-based packs to existing SLA setups is that they try to match nominal voltages, instead of charging voltages. The motors and controllers have to have the voltage "room" to take an SLA right off the charger, so why not take advantag of that?
The bottomline is that if you are after competition-level performance, and don't care so much about range, RC LiPo packs will certainly give you the most "bang" for the buck. If you aren't interested in all-out perfromance, but need more range, while still wanting lightweight, get a 16 or 20Ah Ping pack. If you still want closeto the same all-out performance, but want a pain-free charging solution, nothing beats a123s.
-- Gary
A cell level LVC capability can prevent this, that's all I'm saying.
And 20mph? Really? Most bikes without electric motors can go 35mph. Whats up with that!!
I WANT EVERYTHING!! 
