Sorry if this is a dumb question, I'm not very smart when it comes to wiring/electronics

I have a old 145 watt psu sitting around. Would it be strong enough to power a 50 watt 5 amp DC charger?

http://www.cpuboards.com/power-supplies/hp-p1457f3.htm

Yep, it'll work.

It’s right at the edge, depends on the battery being charged. The +12V output rating of 4.5A is 54 watts (12V x 4.5A). The charger consumes some power in addition to the output, might be dicey to get the full 50W output reliably. Generally a modern charger will consume 10 to 20% (efficiency of 80 to 90%).

But if charging a 2S lipo, the charger will only have 42 watts of output due to the 5 amp limit (8.4V peak voltage x 5A). Should be OK, but not much extra for a safety margin. If you convert it watch temps carefully for the first few charges.

Also be aware PC supply conversions vary in their ability to maintain a useable voltage at full power.

Larger PC supplies are fairly plentiful and not terribly expensive, especially if you can find some used ones for cheap or even free, might be worth finding something bigger before putting the effort into converting it for RC use.

it will be charging 2s batteries.

i also have a 250 watt power supply that i can use if this one doesn't work out.

yes the 145 watt will power your charger and then some since its a 50watt charger..only issue i see some chargers like ICE dont like the 11.73 volts the psu's have..

Well, I just finished it up. What kind of temps should I look for? I'm going to charge 2 of my 2s lipos and watch the temps.

Here are some pics.

Those low-power half-wave style PSU's are also capable of putting out a little more then the rated, in my experience, so I wouldn't worry about it.

Anyhow, that PSU has inbuilt thermal protection. It'll shut down if you overload it.

youwish16- For some added safety, use an E-Fuel power strip between the power supply and charger.

i need to look into that. thanks for the tip

here is a second one i made, 300 watt. didn't put a switch on this one because it had one but i did add a LED light so you can see when it is on.