figuring out Horse Power

[BrianG]

Originally Posted by magman

I played with the calc a bit...and it says that I should have around 3HP. I thought w/the 1520 on 5S that I would have a bit more

You really need a logger for any level of accuracy, but you can get a rough estimate:

1) Calculate average current draw by using runtime and amount of Ah put back into the pack. Example: If you are getting 15 minutes on a 5s 6Ah pack, that's 24A average current (6Ah*60)/15 min.

2) You can probably assume ~3.7v/cell average voltage. Using the same example pack, that's 18.5v.

3) Multiply the two to get watts. Divide that by 746 to get HP. So, that's 444w, or 0.59HP.

You can very roughly estimate peaks by assuming current spikes ~6 times the average value. You can assume voltage will drop to ~3.4v/cell on those spikes. Then, repeat step 3 again. For the example numbers above, that would be 2448w, or 3.28HP.

Peak HP specs are just for bragging rights because those spikes are so short. And really, it's the torque on these motors that is what is so impressive.