

Orlando
Joined Jun 2003
338 Posts

Discussion
Formula for Calculating Battery Runtime?
Hey guys,
I was wondering if there are any online calculators or What the Formula is for Calculating the amount of Runtime for a battery, at a Certain Amp draw, at a certain voltage. For example, a 3cell Lipo 1500mah capacity, being drawn at 10amps would last how long until the recommended voltage cutoff? Simple math makes me think that the answer would be 1500mah capacity/10,000mah amp draw= (.15hrs * 60)= 9mins How wrong am i guys? Appreciate your info Luis 



Orlando
Joined Jun 2003
338 Posts

Sweet,
GoldStar for me! haha 


Joined Oct 2005
552 Posts

Flight time calculator
Quote:
Bob 



USA
Joined Jan 2002
5,080 Posts

Quote:





Actually, two variables are left out, voltage and resistance, so Ohm's law is not applicable here. The only applicable factors are the current draw and the battery capacity in ampere hours. A 1500 mah battery can be just one cell or made up of several cells in series. Regardless of how many cells there are in the pack it will still deliver only 1.5 amps in one hour or 10 amps in 0.15 hours, or 9 minutes.
Where voltage comes into play, is that as the voltage increases, the load, i.e. prop size, has to decrease to maintain the 10 amp current flow. But, as long as the 10 amp draw is maintained, the time to deplete the battery remains the same regardless of the voltage. Larry 


san diego, ca.
Joined Sep 2000
252 Posts

Here ya go Luis, & its FREE! HTTP://brantuas.com/ezcalc/dma1.asp I have used this program many times to calculate; What Motor, What Prop, How many Batteries, and you will get your run time, Amp draw, and amount of Thrust. Fast Fly



Orlando
Joined Jun 2003
338 Posts

FastFly,
Thanks for the link, i have been using pcalc for a long time, but it doesnt have the newer motors that are out. Pcalc is really good, but lacks in motor selection. 
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