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DIY 12volt battery charger.

1638 Views 5 Replies 5 Participants Last post by  Looby
while digging thru my STUFF looking for a plumbing tool in my tool room, i came across a timer controlled 12 volt power supply for out door lighting. i think it is made by INTERMATIC.

input is 115 - 120 volts and the output is stated as being able to handle ''7 lights of 11 watts each''.

can i use this to charge 12 volt car batteries?

i was thinking of setting the timer for the shortest time possible 30 - 60 minutes probably and then letting it do its thing. maybe even using a second timer so it only came on once a week to keep a battery topped off.

i know REAL battery chargers are more complicated, but i just don't know what damage i may cause.

and finally, is there anything SIMPLE i could add to the charger to prevent possible damage. keep in mind my electronic knowledge stops right after, W=V x A and in house wiring, there is a HOT wire, a COLD wire and a DRAIN. oh yeah i almost forgot, white to brite, black to brass, and green to ground.

thanks,
john
1 - 6 of 6 Posts
It will probably work for simple charging needs. Measure the output with a meter at no load. Then measure the battery alone, then measure the battery with the charger connected and operating.

If the 1st measurement is anything under 16 volts you should be ok, proceed to the 2nd & third test.

You should see a slight increase in the voltage between the 2nd and 3rd measurements. This reflects power going into the battery.

If the third measurement is much over 14v you might not want to continue using it due to insufficient regulation.

You should babysit this thing the first couple of times you use it, just until you're sure it's going to be fine. You don't want to boil the electrolyte unattended etc.

Also make sure you have adequate ventilation- the battery will emit a very small amount of highly flammable hydrogen during the charge. No big deal in the open, but in a confined space this can be an issue if it accumulates.

Extended usage with an improvised charger can contribute to sulfation in the batteries, but for the occasional top-up you're good.
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Are you sure the item converts ac to dc? The output should be dc for the battery, not so?
The output is not rectified. It is AC, not DC, because light bulbs don't care and no manufacturer would put in un-needed components. Do not try this as it could be dangerous.
The output is not rectified. It is AC, not DC, because light bulbs don't care and no manufacturer would put in un-needed components. Do not try this as it could be dangerous.
Seriously? I guess I would never expect anyone to use a 12VAC system outdoors... I agree they wouldn't bother to put in extra gear, but I also wouldn't consider that to be extra.

A simple test with a voltmeter will prove it one way or the other.

Canubaru- If it is AC output, then Radar is absolutely right- don't connect it to a battery. If it's DC you're good.
Get the model number and look it up at http://www.intermatic.com

Betcha a 6-pack that the 12V output is AC, as Radar said.

I'm 100% certain that the my indoor low voltage lighting is AC,
and can't think of any reason that outdoor would be different.

Looby
1 - 6 of 6 Posts
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