Of course.. it seems obvious now lol. Both questions I asked. I really should of thought about that series connection thing. I've done plenty of these hack jobs before, usually just loading the 5v though

Cheers for clearing it up.

Thought as an electronics enthusiast with no formal training, I have another couple questions :)

You said you needed to draw about 1A for the feedback circuit to work properly? How come using diodes you only needed 250ma?

And if you have a psu with multiple 12V rails, can you parallel the rails to achieve the psu's total rated 12V power?

When I was using the voltage divider circuit method, 1A was needed reason for the calculations to work right. Only when I used the diode method did things work right mathematically, and actually. Besides, drawing 1A all the time reduces the available current for the real load (charger), so it all worked out in the end.

The PS specs do say 0.8A min is needed, but it seems to work fine with no load. However, I am drawing 0.250A, and the fan draws about the same, so it's close to the spec'd 0.8A.

Can you use this power supply to charge lead acid batteries?

I'm not familiar with lead-acid charge profile, so I cannot say. But I do know that the supply's output voltage has to be higher than the battery voltage for any kind of charging to take place. But what type of current limiting, if any, is needed, I dunno.

I had a charger that charged two sla batteries in a series at 29v and 2.5a. It looks just like a power supply for a laptop or something like that. I accidently fried that so now I need to buy a new one or get something like a pc power supply to work.

wait. Will a car battery charger work? Dang, it probably will. We got one and never used it. I'll look into that.

I am still thinking about getting a pc power supply. I told my dad to look out for an old computer at work and take it home. I hope I can find one!

He needs to update the lithium battery page. Hasn't been changed since 2006. :oh:

yeah, still an interesting read though :p

http://xkcd.com/560/

Heres mine :mdr:

http://i191.photobucket.com/albums/z...3/HPIM1984.jpg

My hyperion 0610i is rated for 250w. If I get a ps rated for 250w, can I expect 20a@12v? 500w = 40a@12v?

Newegg has a lot of cheap power supplies for around $20, or even less. The OP is over 3 years old, and it said a suitable PS would cost about $40. Can these $20 power supplies be trusted?

Maybe this one? - http://www.newegg.com/Product/Produc...82E16817709011

First of all, you want to figure in a typical charger efficiency of ~80%, and then I like to add another 15% as a safety margin. So, that 250w charger will require around 370w. Assuming the PS can deliver a stable 12v, it needs to be rated for at least 31A.

When shopping for supplies, make sure that they don't have multiple 12v rails. What you want is a single high current 12v rail.

No. A huge chunk of the power, especially on older PSUs is on the 5V and 3.3V rails. You want to look at the stats of the PSU and get something with a single 12V rail that can handle a lot of grunt. These also happen to be the most expensive kind :)

Something like this would be good, dunno how much you're willing to spend though. This is the cheapest quality PSU that looks like it will do the job is

http://www.newegg.com/Product/Produc...pk=CMPSU-400CX

Details under 'resources' tab here
http://www.corsair.com/products/cx/default.aspx

30A @12V = 360W seems ample :)

edit: I just noticed the one you linked has the output table in one of the photos. IT is rated for 25A @ 12V, or 300W which seems like it could be OK. That is, of course, inferring from that table that it is a single 12V rail. It is plausible it could have multiple rails, and could be giving a combined 12V power rating.