How long can a laptop run off a car battery when the engine is left off??
08-04-2003, 01:38 PM
#1
U wanna try me young boy?
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Join Date: May 2001
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How long can a laptop run off a car battery when the engine is left off??
Can someone check my math for me...
If I have a laptop that uses 60w and I power it from a car battery, how long will it last?
The Amp Hour rating tells you how much amperage is available when discharged evenly over a 20 hour period. The amp hour rating is cumulative, so in order to know how many constant amps the battery will output for 20 hours, you have to divide the amp hour rating by 20. Example: If a battery has an amp hour rating of 75, dividing by 20 = 3.75. Such a battery can carry a 3.75 amp load for 20 hours before dropping to 10.5 volts.
A 110v/40w load is .5 amps. If a 75 AmpHour battery can carry 3.75amp load for 20 hours, then is shoudl eb able to carry a .5 load to 137 hours, nearly 6 days - yeah?
So a 60w laptop plugged into a battery should last 6 days - is this right? 6 days would be the longest the car could sit wihtout being run until the battery drops to 10.5V (and won't start the car after that)
If I have a laptop that uses 60w and I power it from a car battery, how long will it last?
The Amp Hour rating tells you how much amperage is available when discharged evenly over a 20 hour period. The amp hour rating is cumulative, so in order to know how many constant amps the battery will output for 20 hours, you have to divide the amp hour rating by 20. Example: If a battery has an amp hour rating of 75, dividing by 20 = 3.75. Such a battery can carry a 3.75 amp load for 20 hours before dropping to 10.5 volts.
A 110v/40w load is .5 amps. If a 75 AmpHour battery can carry 3.75amp load for 20 hours, then is shoudl eb able to carry a .5 load to 137 hours, nearly 6 days - yeah?
So a 60w laptop plugged into a battery should last 6 days - is this right? 6 days would be the longest the car could sit wihtout being run until the battery drops to 10.5V (and won't start the car after that)
08-07-2003, 05:09 AM
#2
i have mine plugged in all the time and i leave it on usually overnight and no problems starting. i left the key on while working, car not running (headlights stay on,DRL, and the radio on, after an hour i needed a jump. it depends on your battery and the ammount of use the laptop is creating
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