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Battery Charging Question (simple im sure)
By Muffloj, Section Storage Posted on Mon Sep 05, 2005 at 09:43:11 PM MST
..

I just purchased a 12v 9ah exxide battery to power some portable applications. It calls for a 500mah trickle charger ( 12v i presume) which i dont have. I do have an extra 12v 500mah rated dc converter plug scavenged from something thrown away i imagine. I am curios as to if i can cut the output plug off of the dc converter and install a couple +/- clips and use this to charge my battery. If not il put up the 20$ for the small charger.
Thanks for anything.

Battery Charging Question (simple im sure) | 4 comments (4 topical)

Re: Battery Charging Question (simple im sure) (3.00 / 0) (#1)
by wdyasq on Mon Sep 05, 2005 at 05:09:42 PM MST

12V batteries need about 13.8V or so to fully charge and 14.4 is consideered an equalization charge. A 15V 300-900ma charger would work. Your 12V might put put out more voltage than the 12V and should be checked first.

Ron
Adventure is just bad planning." -- Roald Amundsen

Re: Battery Charging Question (simple im sure) (3.00 / 0) (#2)
by maker of toys on Tue Sep 06, 2005 at 02:22:50 PM MST

the 'wall wart' sort of power supply is usually poorly regulated in voltage; it may actually be as much as 18V OC, so when you test it, put it under a load. (Not a short circuit. . .)

probably the BEST way to test it would be to hook a Digital Ammeter into the circuit, and actually connect it to the battery. if you get 100+ mA into the battery (depending on state of charge), then it'll be fine for your needs. if you do go that route, be sure and check the volts across the battery during the charge regularly for the first couple of charge cycles. . . you don't want the volts to drift up into the 'fried battery' range (above 14.5V) and stay there.

-Dan

PS: most hobby shops have cheap battery chargers for that size of battery. . .

It's not a case of 'Save the planet,' it's a case of 'Save the humans.'

Re: Battery Charging Question (simple im sure) (3.00 / 0) (#3)
by ghurd on Tue Sep 06, 2005 at 02:39:45 PM MST

Maybe a 300ma 18V DC wall wart, regulated with a PB137ACV chip.
Cheap and easy.

Or around a 16V AC 300ma, full wave rectify the output, regulate with the PB137ACV.
G-
Ghurd.info

Re: Battery Charging Question (simple im sure) (3.00 / 0) (#4)
by Muffloj on Wed Sep 07, 2005 at 09:21:05 AM MST

Thanks alot for taking a minute go give some help.

I ended up using the ac/dc converter from an old Sprint cordless phone. @ 13v 1200mah ( it read 14.5v ). I charged for about 6 hours or so checking the voltage on the battery frequently. The battery only became slightly warm after hours of charging and the battery is holding @12.81 volts 24hours after the charge.
Hopefully this will work untill i get my charger thanks again.

[ Parent ]

Battery Charging Question (simple im sure) | 4 comments (4 topical)

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