MacGyver 12v car electrical testing PSU

[Mangtoos]

I've been doing the planning on a couple of mods involving the electrical system of the car when I ran into a problem of test power. I have a decent variable power supply but at 12 volts it only drives 3.5 Amps. Instead of buying bigger variable PSU that supports up to 40amps at 12 volts for about $400, I decided to see if I could find an alternative. I have some server power supplies lying around, and server PSUs are really good at driving heavy load at 12 volts. The hard part is trying to figure out how to actuate the PSU to turn it on. I took one of them apart and traced the connections to identify the three pins that were responsible for telling the PSU to power up. Once I had it, I wired the pins together through a switch so I could toggle the power on and off. Here is the result:

http://custodela.com/p/psu.jpg

12 volt power supply that can provide up to 100 AMPS constantly. The LEDs are not there for show, but to let me know that the PSU is on and supplying power. I might consider adding a voltage or amperage display at some point. The main line is a 10AWG that leads to a XT90 connector that I could plug different things into. I could technically build a few of these then connect them together in parallel and boost a dead battery if I wanted to.

Now I can test any electrical modification properly prior to putting it in the car. I could also disconnect the battery and connect this into the car when running things without having to have the engine running, or worry about draining the battery.

[XTOTHEL]

You can get power supplies on eBay...40amps for about $30. Though I'm not sure how reliable they are, probably no protection built in. I had one break on me (doesn't provide enough amperage). So I did something similar with my old computer PSUs. I'm not sure about server power supplies, but for my PC ones, each rail had a their own max amperage rating. So double check on that.

[Mangtoos]

You can get power supplies on eBay...40amps for about $30. Though I'm not sure how reliable they are, probably no protection built in. I had one break on me (doesn't provide enough amperage). So I did something similar with my old computer PSUs. I'm not sure about server power supplies, but for my PC ones, each rail had a their own max amperage rating. So double check on that.

That's why you'd use a server PSU. It's a single 12v primary rail usually. Chinese ones would be hit and miss depending on the capacitors and FETs they use. You also want to be sure they tolerate shorts. That said, a half decent 100Amp Chinese one would run $150 minimum, where you can find used 1000w server PSUs on ebay for like $20-30 where you're pretty much guaranteed good quality.

[lawlzen]

Excellent work, Mengtoos.