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Aug 26th, 2013, 04:45 PM
#1
unsure of battery life calculation
I'm trying to calculate the life of a battery:
duty cycle: 3%
current drawn during activity: 1.53 mA
current drawn during inactivity: negligible
transmission time: 33 ms
battery capacity: 2510 mAh
here are my calculations, but I could be wrong here:
Battery capacity: 2510 mAh
Current drawn in 1 hour = (1.53 mA / 3%) x 100%
Current drawn in 1 hour = 51 mA
Battery life in seconds = ((2510 mAh / 51 mA) x 60 minutes) x 60 seconds
Battery life in seconds = 177176.47 seconds
Battery life in seconds = 1.77 x 10^5 seconds (3sf)
any advice would be appreciated, as I really want to get a clear understanding of this calculation, + the tuition I received was inadequate. thanks
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Aug 26th, 2013, 05:44 PM
#2
Re: unsure of battery life calculation
If the duty cycle is 3% that means that the device is active only 3% of the time. So you need to multiply the current drawn by 3/100, not divide it. You don't need "in 1 hour" on lines 2 and 3. So in my view your calculation should be:
Battery capacity: 2510 mAh
Current drawn when active = 1.53 mA
Current drawn, average over duty cycle = 1.53 mA * duty cycle = 1.53 * 3 / 100 mA = 0.046 mA
Battery life in hours = 2510 mAh / 0.046 mA = 54565 hours
Battery life in seconds = 54565 * 3600 = 196,434,000 seconds
Battery life in years = 54565 / 24 / 365 = approx. 6 years.
But don't get too excited. In the real world batteries run down even when you are not using them. Normal NiMH batteries (which I guess you are using given the capacity) lose about 30% of their charge per month through self discharge, so you will probably need to charge them once in 3-4 months if that is the type you are using. Li-Ion and special low-discharge NiMH batteries keep their charge much longer.
BB
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Aug 26th, 2013, 05:56 PM
#3
Re: unsure of battery life calculation
thanks for the reply boops
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