Repurposing a Dell power brick

Charging what voltage battery?

You may need to raise the output voltage a bit if you are thinking of charging a 12V battery with it.

Some SMPS need a minimum load to start. You might find without that, you won't find an open circuit voltage to measure.

I used to use a "boat anchor" type MFM hard disk drive as my start up load, but that was years ago.

Also, think about adding fuses in series with what you add to it.

Indeed, there's what looks like a trimpot inside the case. It turns out the anti-tamper screws were defeated by a small flat screwdriver jammed between one spline and the center post.

Just tried a lightbulb with ~2.3 ohm cold resistance across the output. Nothing.

After a bit of fumbling, it turns out the "remote" line needs to be pulled to ground, which puts 11.99 volts on the output. That's lower than I'd hoped, but it's a good start. The unit looks nicely made, it would be pleasing to salvage it.

Thanks for writing!

bob prohaska

That's the unit I have. The adjuster that I thought might be for voltage seems to have no effect, leaving the no-load output at

Thanks for writing,

bob prohaska

Its not a battery charger its a very well regulated 12 volt supply. Do yourself and the batteries a favor and get a battery charger.

Plenty of vids on youtube if you search for

smps increase voltage

or similar.

Take care, one hand in pocket etc...

Whereas I value and appreciate repurposing all sorts of devices, when it comes to battery charges, I tend to draw the line, as much by class as use:

a) Lead Acid batteries store a tremendous amount of energy using dangerous chemicals that if released suddenly can (and will) cause massive physical as well as environmental damage. With this class of batteries, I try to use only 'smart' chargers designed for the purpose and intent. Nor do they like being over-charged. b) Gel Cells (Gates Trademark) tend to be more stable than the typical lead-acid battery, but really do not like being overcharged. They, too, can explode. c) Lithium batteries in their various types - as above, with a curious ability to burst into flames if abused. d) Ni/Cd batteries, while quite tolerant of high charging voltages - initially - do not like to be overcharged, and can be damaged in that process.

You pays you money, you takes you chances.

Peter Wieck Melrose Park, PA

You will still need a battery charger circuit added to your brute supply to become a battery charger.

I've repurposed a bunch of wall bricks by changing the fixed voltage they normally run at. Find the smps controller IC on the board and get a datasheet on line. With that, you'll get a representative circuit that will show you the feedback circuit and associated input pin. Fudge resistor values from the opto coupler to the feedback pin to adjust the 12V output. On some, I've added a trimmer to adjust the value as needed.

I shouldn't have called it a battery "charger". "Booster" would have been a more accurate term. It'd be set to, say, 13.8 volts with the actual CC/CV charger set to 14.4 volts. That way it could add a little extra current in the early phase of charging and then become insignificant at the end.

It's too tightly packaged to be easily modified. Can't even get a good look at the board without taking the heatsinks off. I'll look elsewhere....

Thanks for writing,

bob prohaska