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stev32k
Premium
join:2000-04-27
Mobile, AL
kudos:1
Reviews:
·Mediacom
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·AT&T Southeast

Cheap battery charger

I bought a new generator last year that came with a 12 V, 0.75 amp power supply. The power supply plugs in to the generator to keep the battery charged up while the generator is not in use and it works well.

I thought that was a pretty good idea so I rummaged around my pile of old power supplies and found one that is 12 V, 0.5 amp. I cut off the connector, split and stripped the wires, and attached alligator clips. Then I hooked it up to my riding lawn mower battery that is always dead after setting all winter. As expected the battery was dead. After three days I tried it again and it cranked the mower up.

What I don't know is can the battery be damaged by over charging and how can I tell when it is charged enough?



shdesigns
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join:2000-12-01
Stone Mountain, GA
Reviews:
·Atlantic Nexus

What you want is a float charger.

I had a trickle charger (100 milliamps.) Left it on my motorcycle and after a few months, the battery measured almost 16 volts and was out of electrolyte. It never recovered.

Fully charged, a battery will read about 13.1 volts. If you connect a battery to a 13.1V power source it will charge up fully but get exponentially slow. Will charge to 75% in say 2 hours, 93% in another 2 hours, 95% 2 hours later and so on. Eventually it will draw almost no current.

A "battery tender" or "float charger" costs as little as $10 (at places like harbor freight).

Using a wall wart may work but it may also overcharge.
--
Scott Henion

Embedded Systems Consultant,
SHDesigns home - DIY Welder


lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to stev32k

said by stev32k:

I rummaged around my pile of old power supplies and found one that is 12 V, 0.5 amp. I cut off the connector, split and stripped the wires, and attached alligator clips. Then I hooked it up to my riding lawn mower battery ...

If it was a 12V/500mA switching power supply, output voltage would been too low for charging up that idle lawn mower battery.

So I am guessing it was supplying unregulated 12V which is actually higher voltage than 13.x V DC recommended for safe trickle or float charging.

There is an active 12V battery charging thread in the electronics forum where you will see some schematics of the extra stuff required for such an adapter to build a proper charger.


cdru
Go Colts
Premium,MVM
join:2003-05-14
Fort Wayne, IN
kudos:7
reply to shdesigns

said by shdesigns:

Using a wall wart may work but it may also overcharge.

If the battery already has a charge and you just want to maintain it, putting the wall wart on a simple timer can do the trick. Running it say for an hour a day should be more than enough to keep it charged but minimize the overcharging effects.

But yeah, a float charger is the better solution.


stev32k
Premium
join:2000-04-27
Mobile, AL
kudos:1
Reviews:
·Mediacom
·DIRECTV
·AT&T Southeast

said by cdru:

said by shdesigns:

Using a wall wart may work but it may also overcharge.

If the battery already has a charge and you just want to maintain it, putting the wall wart on a simple timer can do the trick. Running it say for an hour a day should be more than enough to keep it charged but minimize the overcharging effects.

But yeah, a float charger is the better solution.

Putting it on a timer is a good idea. Hadn't thought of that. I have no idea what kind of power supply it is or where it came from. Every time I get rid of some electronic device I save the power supply. I have a whole box full of them that I've collected over the years. Some must be at least 15 years old.


shdesigns
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Premium
join:2000-12-01
Stone Mountain, GA

I've put trickle charges for R/C planes, cordless drills etc on a timer. It worked well



Draiman
Let me see those devil horns in the sky

join:2012-06-01
Kill Devil Hills, NC
Reviews:
·Verizon FiOS
reply to stev32k

Here's a good product for that.
»www.amazon.com/Battery-Tender-02···+battery
--
What we're saying today is that you're either part of the solution or you're part of the problem. - E. Cleaver 1968


boaterbob
Premium
join:2005-08-01
Moncks Corner, SC

1 edit

$40 - TODAY ONLY from Sears - charger and maintainer:

»slickdeals.net/f/5876060-DieHard···e-pickup