I have the E-flite Tensor 4D with the Park 370 outrunner 1360Kv motor and the Phoenix-10 ESC and a 10x4.7 prop.

I tried to run the Electrifly 1200mAh 7.4V 2 cell Li-Po pack but the ESC shuts down after about 20 seconds at full throttle.

The ESC manual tells me this is due to the motor drawing too much current.

Do I have the wrong battery or do I need a bigger ESC or is the prop wrong?

I searched for some type of formula to figure it all out, but I'm not much good at higher math anyway

Any suggestions would be greatly appreciated.

Actually, your pack will work OK if you simply switch to a smaller 9x4.7 prop. Your current 10x4.7 prop is pulling around 13 amps...too much for your 1200mAh pack. Under the 13 amp load, your battery is dropping to below 3v per cell which is causing it to hit the LiPo cut off on your ESC (if you have it set properly to a 6v cut off).

In the future, you might look at lighter, more powerful batteries for your Tensor. The Thunder Power 730mAh packs deliver more power than the ElectriFly 1200s while weighing almost half as much. The E-flite 860mAh packs are also a great choice weighing just a tad more than the TP730s. I fly both of these packs on my Tensor and the performance is excellent.

Good luck,

Jason Merkle
E-flite Product Manager
Horizon Hobby
http://www.horizonhobby.com

Ross: Please review the Kokam HDR packs at www.fmadirect.com You will find the KOK 910 or 1250 to be the ideal match for your Tensor and with the added benefit that the cells can withstand up to 18.5 V/cell per cell over charge without igniting in the event that you should ever have a charger malfunction. The Kokam packs have pc terminals that let you check cell balance and strain relief for the output wires. The packs are available from FMA from the web site, from Horizon, Tower Hobbies, Hoby Lobby, or any of the dealers to whom they distribute. Full service and great customer care are available at FMA as well as all the accessory products to make you successful with Li Pos.

Hi Ross,

The ElectriFly 1200mAh pack can only deliver about 6amps and your setup demands more. This is why your ESC is shutting off the motor.

Any of the cells suggested by Jason or Fred will work better as they have more current delivery capability than your 1200mAh cell.

You can either reduce your prop size to reduce the current demand within the 6amp limitation of your 1200mAh cell or choose a more appropriate cell for your power system.

Good luck!