Originally Posted by IntegrityHndywrk
To make a profit on people that don't want to go though the trouble or don't know how to modify a PC power supply. To be honest, some of those power supples are worth spending the money on because they have lots of protections and better circuitry. So they may last a long time. But i'm kind of skeptical of most of them. But, you can go buy a computer ATX power supply for about $80-100 or something. It's been a while since i had to buy them. They probably are a little more than that now. But they are not as much as the charger power supplies people sell for their chargers, typicaly. Plus you might just have one laying around in one of your 15 desktop computers the kids never use anymore, or whatever. Someone has one laying out in the trash right now ready for pick up, somewhere. Most of the time they just get thrown away. There is also pure 12V regulated power supplies for testing electronics and things of that nature. I have a 30 amp one in my workshop but i don't use it for my chargers. These bench power supplies are also very costly, so i don't want to burn mine out charging batteries. So lots of people also do this mod to avoid the high cost on bench power supplies.
The way ATX power supplies work is a lot like how the BEC works on our helicopters.By using "switching" it regulates 3 different voltage outputs and steps them down from 110-220v AC. By simply tricking the power supply into thinking the PC's power button is on, you can use the power supply any way you like. Here is a pretty decent video i randomly picked just now to explain it better.
Oh yeah, for our purposes all we really need is the 12V part. All the rest can be removed really. But you really must be careful with this. You also need to be sure your charger is powered sufficiently. I prefer to have head room. So a 200 watt charger needs at least 200 watts. I am using a 400 watt PSU at the moment i think.
I use one from a decommissioned server from work. Actually not a server but a security appliance. The power source provides 13A on the 12V rail and has a built in fan and power switch. Since my charger is only 5A, I have plenty of room left, that might change one day if I ever upgrade to a larger heli and packs.
The conversion took about 1 hour, that includes dismantling, cleaning, removing 5V and 3.3V rails, soldering new wires for 12V and a plug. Then I put some rubber feet underneath and that's all.
The one I use is a Sunpower SPX-6200A1 and occasionally can be found on ebay. What I like about it is that it is really small, 10x18x4 cm, do your math in inches if you like.