Charging a car battery using a 12v laptop charger

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  #1  
Old 11-28-11, 12:56 PM
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Charging a car battery using a 12v laptop charger

I occasionally need to charge the battery on a Toyota Echo that I rarely use. I am considering using an unused univeral 12v 60 watt laptop charger for this, as I would get about 5 amps that is current limited from the charger and it would charge the battery overnight. I've Googled and Googled this subject and nothing comes up...maybe people are afraid of liability issues.
Does anyone have any thoughts?
thanks, Jim
 
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Old 11-28-11, 01:10 PM
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Welcome to the forums.

How do you envision hooking this up to the car? Whether it's going to work in the first place is beyond me but I can't figure that part out to start.
 
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Old 11-28-11, 01:27 PM
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How about plugging into the cigarette lighter Not to be construed as an endorsement of the idea.
 
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Old 11-28-11, 01:27 PM
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Lead acid batteries need a higher voltage to charge. Your average 12v car battery is usually charged at 14-14.5 volts. At rest I think a fully charged car battery is about 12.6 volts and it does not drop down to 12v until it's at about 45 or 50%. So, if your power supply is putting out 12 volts I don't think it will charge the battery.
 
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Old 11-28-11, 06:00 PM
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To answer replies,
1. I'd solder some alligator clips, like on jumper cables, onto the charger lead and connect to the battery terminals.
2. My laptop charger also has a 16v output.
Jim
 
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Old 11-28-11, 07:38 PM
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16 volts is too high for regular charging. An intelligent fast charger can get away with it by carefully monitoring what's going on and varying the amperage and voltage as needed. A constant 5 amps of 16 volts will cook a lead battery. If you were stranded in a blizzard and had to emergency charge for one start to get to safety it's an option but it's too hard on the battery for regular use.
 
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Old 11-28-11, 09:39 PM
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yeah, I have thought. buy a 20 or so worth float charger, hook it up and let it be. there's a specialty store called Alphatronics around here that carries those.

geee, even better:

Grip Tools 38020 12V Automatic Battery Float Charger
 
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