3s 4000 or 4s 3000

[Glyn R]

I was just thinking that the real capacity of Lipos is watt/hours. So 4.0 amps at lets say 11.1volts is 44.4 watt hours. 3.0amps at lets say 14.8volts is 44.4 watt hours. So flight times under the same loadings ant throttle will be the same.

[Simon Chaddock]

Glyn R

This would only be true with different motors appropriate for the voltages.

The higher voltage set up would require a proportionally lower kV motor to drive the same prop at the same speed using the same Watts.

Technically the higher voltage set up would in theory be very slightly more efficient as the current would be smaller and thus the resistance losses would be reduced.

[Chris Bott - Moderator]

Absolutey right Glyn, which is why our mains electricity is measured in KWh.

If we had two identical models with appropriate motors and props for two different batteries, flown at the same power, a 4S battery of the same capacity would last longer than a 3S.

So a rating in mAh is only part of the story about the capacity of a battery.

Edited By Chris Bott - Moderator on 24/04/2013 18:10:32

PS - That will teach me to read the OP properly, I think my answer makes proper sense now!

Edited By Chris Bott - Moderator on 24/04/2013 18:11:54

[C Norton]

What Simon says.... And that current reduction might be enough to let you use a lower rated ESC and smaller diameter wires and connectors for slightly less weight and expense.

[Glyn R]

I put this because I have just changed a model I have flown on 3s 3000mah for a while to 4s 3000mah, the motor ESC and prop are the same of course it needs less throttle most of the time but does fly longer. I did check the loadings on the ESC etc.

[Simon Chaddock]

Glyn R

With the figures you quote you are increasing the watthr capacity by 33% so it should indeed fly for longer but not by the same amount as the extra battery weight will need a bit more power to fly.