I'm using a Kokam 1250 3 cell Lipo on an AXI 2212/20 with an 8 x 6 electric APC and a phoenix 25 speed contol. At full throttle it draws 17.4 A according to an Astro wattmeter. From a fresh charge at full throttle the battery voltage drops from 12.45V to 9.1V and cuts out on the speed control. I don't understand why the voltage drops that fast if the pack is rated for 18.75A continuous. Any ideas

A similar effect was reported by Steve Neu in the April issue of Quiet Flyer magazine for the 15C 910mAh cell. The 640mAh cell, however, did appear to perform well at 15C with about 3.5v under load.

I suspect that the initial lot of cells may not be performing up to specifications. You may want to measure the pack voltage under a 10C or 12C load to see if it is closer to 3.5v/cell.

The next size up cell to fit your needs with minimal weight increase would be the ThunderPower 2100mAh cell or the Kokam 2AH cell.

Anyone else have these 1250 Kokam batteries with similar results?

you may find its down to thin wires from the battery to the esc? or a poor connector? it it has that little red jst type, your stuffed wanting 17 amps through it. try runnoing the motor below the cutout speed for a couple of mins and check the temperature of the wires? if they are on the hot side of warm they are not heavy enough. i had a similar problem with an over propped shocky on 3 cells lipo. i programmed my esc to 2.7 volts per cell instead of 3, works ok and the batteries are still good.