Lipo-runtime

HI
I've an ofna hyper 8 pro buggy converted with a 1415 /1.5D (2700kv) Neu and M.troniks beast esc. It's geared 16/46 and weights 7.27 lbs. I need a 3s lipo battery for 15 minutes runtime on race conditions without performance drop. How big should this batteries capacity? I want to have the lightest battery for my needs.

[BrianG]

It will be hard to give an exact figure because everyone's setup changes. Plus you want max runtime on the smallest battery possible, so that doesn't leave much room for error. The only way to get a true estimate for your situation, drive style, track conditions, etc would be to use whatever 3s battery you have right now (maybe borrow one?), run it, calculate average current draw with that setup, and then calculate required mAh for 15 minutes of running with your calculated average current draw.

The motor is on the way now so I don't have the chance to try it right now. I found a good quality lipo for a good price and don't want to miss this opportunity. Can you say at least if a 5000mah 3s lipo will be enough for 15 minutes with configuration above.

[BrianG]

It might be possible. I get around 20 minutes on 4s 5Ah on a similar kv 1512 motor in my Hyper 8. That equates to ~15A average draw, or 222w average power. On 3s, that same power level requires 20A average current, which should get you 15 minutes on the button. Again, calculating runtime is NOT an exact science, so lacking a setup to try, the best you can do is compare against other similar setups and guess as close as you can.

That info is very usefull for me. Last question. What is your gearing for 20 minutes runtime?

[BrianG]

As I said in my PM, I believe it's 46/15 or 46/14, somewhere in that range. Again, that's on a 1512/2d (kv=2650) on Turnigy 4s 5Ah.

Thanks a lot. That info is a good starting point for me.. The motors are very close (2650kv 1000W and 2700kv 1100W) I need not much topspeed so I'll use 15t pinion on 3s to save some current.I assume a quality lipo around 5500mah will be enough for me..