HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Nov 21, 2006, 02:08 PM
Registered User
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 cut-off?

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
GWSLAWNDART is offline Find More Posts by GWSLAWNDART
Reply With Quote
Sign up now
to remove ads between posts
Old Nov 21, 2006, 02:26 PM
Registered User
Staffs, UK
Joined Nov 2003
10,561 Posts
Simple math is all it takes. You've answered your own question .

BTW voltage doesn't make any difference, it's only current draw and capacity that count.

Steve
slipstick is offline Find More Posts by slipstick
Last edited by slipstick; Nov 21, 2006 at 04:59 PM.
Reply With Quote
Old Nov 21, 2006, 04:15 PM
Registered User
Orlando
Joined Jun 2003
338 Posts
Sweet,

GoldStar for me! haha
GWSLAWNDART is offline Find More Posts by GWSLAWNDART
Reply With Quote
Old Nov 21, 2006, 05:40 PM
Registered User
USA
Joined Jan 2002
4,787 Posts
Quote:
Originally Posted by slipstick
Simple math is all it takes. You've answered your own question .

BTW voltage doesn't make any difference, it's only current draw and capacity that count.

Steve
Why is voltage irrelevant?
Ohmic is online now Find More Posts by Ohmic
Reply With Quote
Old Nov 21, 2006, 05:46 PM
Registered User
Joined Oct 2005
552 Posts
Flight time calculator

Quote:
Originally Posted by GWSLAWNDART
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.

Appreciate your info
Luis
Try Here:http://www.bphobbies.com/view.asp?id=A0320048&Nav=7
Bob
bob2005 is offline Find More Posts by bob2005
Reply With Quote
Old Nov 21, 2006, 05:59 PM
Registered User
USA
Joined Jan 2002
4,787 Posts
Quote:
Originally Posted by bob2005
I was looking for the theory behind this, not a link to a web calculator. Somehow I recall Ohm's law as having three variables and I didn't think it was possible to leave one out.
Ohmic is online now Find More Posts by Ohmic
Reply With Quote
Old Nov 21, 2006, 06:34 PM
Senile Member
Lnagel's Avatar
Moab, Utah, USA
Joined Apr 2003
6,141 Posts
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
Lnagel is online now Find More Posts by Lnagel
Reply With Quote
Old Nov 21, 2006, 07:47 PM
Registered User
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
Fast Fly is offline Find More Posts by Fast Fly
Last edited by Fast Fly; Nov 21, 2006 at 11:02 PM.
Reply With Quote
Old Nov 21, 2006, 08:21 PM
Registered User
Orlando
Joined Jun 2003
338 Posts
FastFly,

Thanks for the link, i have been using p-calc for a long time, but it doesnt have the newer motors that are out. P-calc is really good, but lacks in motor selection.
GWSLAWNDART is offline Find More Posts by GWSLAWNDART
Reply With Quote
Old Apr 12, 2009, 04:04 AM
Registered User
panzerd18's Avatar
Melbourne, Australia
Joined Dec 2005
827 Posts
BP = Battery pack (in amps)


AD = Amp Draw (in amps)


X = time to deplete 1000mah pack


BPX = time to deplete battery pack

60(minutes) / AD = X

X * BP = BPX
panzerd18 is offline Find More Posts by panzerd18
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Formula for determining battery capacity needed byrocat Power Systems 4 Feb 11, 2007 04:45 AM
Need formula for calculating speed for specifi prop lensrc Modeling Science 4 Apr 08, 2004 05:49 PM
What is the formula for calculating RPM at given Amps austinflyer Power Systems 2 Jan 24, 2004 04:13 AM
Battery Runtime for GWS Zero or other 370 models spyder0069 Parkflyers 1 Jul 26, 2002 02:53 PM
Formula for calculating wing area? Slope Nut Power Systems 14 May 09, 2002 02:54 AM