Can PSU lines be combined to run a power tool?

[TheNiceGuy]

Hello all
I have a spare PSU I'm using to charge batteries. I thought it would be an interesting project to power a couple of 12 V tools ( impact driver, drill, etc.). Not sure how many watts the tools draw, but I would take a stab it would be less than the combined 12 V rail amps (14a+15a =348W).
If it is possible, could I just physically combined the 12v wires and connect? Is there a limit on how long I can make the DC lines to the tool?
Thanks

 

[TheNiceGuy]

Works!

 

[master_shake_]

iirc there was an ad and they used a power supply to jump start a car.

i can't remember the brand for the life of me.

 

[PottedMeat]

what does 'works' mean? does it work under a heavy load? or does the overcurrent protection trip?

 

[uclabachelor]

I don't know about running a power tool but welding metal seems feasible.

1000W pc supply can do about 50-80A of 12V and is no problem for welding!

()

 

[TheNiceGuy]

Just hooked up to the terminals and maxed the tool out etc, did great lines not even warm.
Got me thinking about other cordless tools. Can the lines be run in series somehow to up the voltage, for example 12+5+3=20v?

 

[razel]

Power tools can use a lot of amperage. Becareful as the amp jump up. Power coming out of the power supply is DC. As wires get longer, there's more resistance (heat) and can become a safety issue.

I remember testing an audio amp in my friend's car. We just used the stock 14 or 16 gauge wiring. Amp was barely 200 watts and the stock wiring began to heat enough that the stock wires insulation stuck to one another.

So beef up those wires to the largest gauge you can fit in the connector. That could be 12 gauge.

 

[TheNiceGuy]

Thanks

 

[mindless1]

Just hooked up to the terminals and maxed the tool out etc, did great lines not even warm.
Got me thinking about other cordless tools. Can the lines be run in series somehow to up the voltage, for example 12+5+3=20v?

No, because they share a common ground, and because regulation and protection circuits are based on feedback.

There are people who have burnt up 12V cordless tools running them from a much higher current source that doesn't suffer voltage depression by the time the tool gets hot like it's original battery would, for example extended use with a ~12.6V car or solar panel battery.

Frankly I don't see the point when you can get an AC mains powered corded drill for $30 and not have to tether it to a block of PSU... even less than $30 if apples:apples you get a used drill, at a garage sale or elsewhere.

 

[potzocalli]

Its goods to know it works. Just for the sake of it. A good PSU should have been able to do it if you looks at the numbers involved (AMPS or WATTS mainly).

Good test Nice Guy but I also recommend this as a last resort and better use the proper charger for the tool.

 

[mindless1]

It should be mentioned that the typical connector pins off an ATX PSU are only good for about 6A each, so it wouldn't be hard to find a cordless tool that melts them if you don't have a sufficient # of connectors (and of course wires unless you'll be rewiring the PSU) to handle the current. I'd go with a minimum of 3 connectors (or extracted leads to reduce bulk) but more would be better.

 

[mindless1]

Its goods to know it works. Just for the sake of it. A good PSU should have been able to do it if you looks at the numbers involved (AMPS or WATTS mainly).

Depends. It'd need independent regulation (or highly 12V biased group regulation) or else when you start pulling a lot of 12V amps with no load on 5V, and sometimes even sensing on 3.3V rail too, the unused rails could rise too high and trip the protection circuit.

Even in that case there are ways to hack it to work, if the goal is reuse some old PSU instead of devoting a newer PSU with more value in powering a computer instead of a cordless tool.

The primary way would be monitor the change in the rails causing the protection to kick in and devise (or alter an existing) resistor divider in the rail feedback loop, calculating the divider value or revised value (of an existing voltage divider subcircuit) to put the rail voltage within bounds at the 12V load the tool causes. If that's not enough of a hint to do it *if* needed, you probably shouldn't be poking around inside a live mains powered PSU.