power convert calculation. 3000 mAh backup battery and 5watt CF bulb?
msht asked:
Hi, can someone provide a way to calculation how long a 5watt CF bulb would last on a 3000mAh backup battery? Thanks!
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Hi, can someone provide a way to calculation how long a 5watt CF bulb would last on a 3000mAh backup battery? Thanks!
January 13th, 2009 at 8:15 pm
5 watts is 5 joules per second
3000mAh or 3A-hr battery
Need the voltage on the battery.
Assuming it is 12 volts, then 3 A-hrs is 36 watt-hours
36 watt-hour x 3600sec/hr = 130000 watt-sec or 130000 Joules
130000 Joules / 5 joules/sec = 26000 seconds or 7 hours.
But ratings on batteries vary a lot depending on discharge rate. Plus there are losses to consider, so count on half that time.
.
January 14th, 2009 at 6:28 am
You are missing one important information. What is the voltage of the CF bulb. Once you know that number, divide watts/volts and result will be the current (in Amps). Now divide 3 Ah (3000 mAh) by the current. The result will be the numbers of hours the battery will last.
January 17th, 2009 at 12:13 am
P=I*V
I=P/V
P=5 watt
if V=110 Vca
then I=5/110
I=.045 Amp=45 mA
–>3000/45=66.66 hrs