Speed Calculator

[macr0w]

Originally Posted by BrianG

Ture, lipos peak at 4.2v/cell, but the voltage does not stay there very long at all when running - just take a look at any discharge graph. People generally use 3.7v/cell because that is the voltage the cell is at for the majority of the time. As a matter of fact, depending on setup, the voltage may actually fall to 3.5v/cell or lower during higher current bursts.

Also, it depends somewhat on the user.

- If you are looking for max torque specs, use a lower voltage/cell rating. High torque is generated by high current. High current causes the cell voltage to drop.

- If you are looking for max speed spec, there will be less current draw when the motor is spun out, but the cell still won't be at 4.2v because the current drawn will still pull the voltage down.

It depends on gearing and weight too. If you are geared high and/or have a heavy vehicle, expect more v drop on take-off acceleration due to the current needed. If geared low and/or have a lighter vehicle, v drop will be less.

It also depends on the battery quality and capacity/C rating. A higher quality/capacity/C rating battery will maintain a more constant voltage under load.

I did some speed runs back and forth in front of my house on and off for 30 minutes or so and still had 15.4 volts on my battery this afternoon.

It was SCREEEEAAAMING!!!! The speed and acceleration is mind blowing! I now know what "Stupid Fast" really means.

[Patrick]

Originally Posted by macr0w

I did some speed runs back and forth in front of my house on and off for 30 minutes or so and still had 15.4 volts on my battery this afternoon.

That would be unloaded voltage though. Voltage under load is what's most important, and is one of the main differences between a good battery and a not so good battery. 15.4v does mean that the pack probably had about half is capacity left though.

[macr0w]

Yeah, it's a 25c 5000 mah 4s Polyquest/Enerland pack.

So far I'm really happy with it.