12v lighting & safety system project-an MBc Community Effort

i have some basic questions about this charger. i'd rather not buy another one if i can avoid it.
please, no fancy theory or suggestions, i have other options if this one won't do it.

Mvc-653f.jpg

a) will this work for my 12v 7ah sla?
b) can i assume the "coded" wire is the positive side? (i need to save the end, so i can't strip it to see for sure)
c) will this overcharge (or otherwise damage) my battery if not monitored?

thanks :cool:
 
Should work

You have a half-amp (500 ma) charger there, often called a "trickle" charger. It'll need to run quite a while (overnight, at least) to put any charge on your battery, very little chance of overcharging. If you have a voltmeter, hook it up while charging and when it reads 15 volts or a little better, it's charged up. You can check the polarity of the charger wires too. Radio Shack sells a simple voltage meter:
http://www.radioshack.com/product/i...Id=2032058&kw=voltage+meter&parentPage=search.
 
thanks...

i can't afford a meter, if i could i'd simply buy the right charger...but that voltmeter looks like a nice "wish-list" item for a complete system.

i don't want to destroy the charger's end, so what i'll do for now is make a tiny adaptor-to-alligator clips thingy. overnight charging is fine by me until i get the rest of the system in play.
 
"no fancy therory or suggestions"

The pic is of a power supply not a battery charger. Your battery can be charged at .7A and the charger should drive that current at 14V. A single wet cell provides 2.2V, so 6 of them offer 13.2V at a full state of charge.
 
Augie, I went junk shopping the other day, and at our thrift shops I found boxes of these transformers or Power supplies if that is what you want to call them, anyway they were $.50 Each. I bought at least twelve and some had the adjustable voltages on them.
A bargain, not to be past up!
Some times you have to ask where they keep them. They come from Phones, Radios, computer junk etc. By law, the voltages have to be stamped on them and watts.
Doc
 
ok.

so.

a) yes or no? no? i need 14v .7a?
b) yes or no (maybe no longer matters)
 
A 12V wet cell battery or in this case a SLA (sealed lead acid) will charge at a voltage of 13.8~14.1V. Your battery is rated at 7AH and those can take a max of .7A or 700mA.
A 5AH battery should not be charged at over .5A or 500mA. Kind of a rule of thumb. Some SLA batteries are designed to charge quite rapidly but they cost more than the average bargain SLA battery.

If you can adjust the voltage of the power supply to 13.7~14V you will be good to go. I am not sure how it will deal with having to deliver its full output for 18 hours, so do keep it cool.
 
thanks.

simple is best, so i'm on the lookout for a 14v/.7a.

meantime i have a 12v auto-trickle charger i can borrow. maybe i'll just buy a cheapo if it works out.
 
Augi,

The coding on the wire is not a sure thing, to answer your b question. The only thing for sure is on the power supply you pictured shows the center to be + and the outer to be -. Most of the power supply I have worked with mark the - wire, but this is not always the case.

I feel an actual charger will work much better, as far as battery life goes , than a power supply. IMHO!
 
I am not trying to sell anything.

http://www.allelectronics.com/ > battery charges(on the right)
Note that the 12VDC @ 500mA (.5A) is two stage so it drops down to a very gentel holding charge rate. See how tall it is? Notice all the open areas for cooling. Tiny power supplies have no venting.
.5 amp trickel charges for motorcycles have been around for 25 years, so the odds are good at finding one cheap.
 
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