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Need help with power supplies Answered

I've been reading about electronics for a while and watching the Make podcast and I've finally started making my own projects. Anyway I have some cordless tools with 3 extra batteries but only one of them still takes a charge. So I thought it would be cool if I could put a power supply in one of my dead batteries so that I could plug it into the wall. I've been looking around my garage and thrift stores for a wall wart that would get the job done (the batteries are 19.2V Craftsman batteries I think they pull about 2000ma) but the closest I've been able to find is an old laptop power cord has a DC output of 19v and 3.9amps. So I'm not sure if that will work or if the extra amps will burn out my tools or something. Does anyone know if it would work? If not how can I dial down the amps?


you want to make your cordless tools powered with a cord? the laptop PSU will work, the motor will only draw as much as it needs, however, you will experience some lagg on the tools. the batteries from the power tools could probably put out more then 2amps, i'm thinking something around 7 Amps or more your drill won't be able to give you as much torque as it does with batteries

Well that's good to know, unfortunately I think there may be some sort of safety device (or maybe it's just dead) on my power supply because when I hooked it to an old 18v drill the I got for free it didn't do anything. Oh, and the reason I wanted to make an ac adapter for my tools was so that I could still use my tools while recharging my battery since I only have one that works. Thanks for your help.

that adapter... connect it to your drill, press and hold the trigger, then plug the power supply to the outlet have you tried using a battery with the drill? did you verify, that the PSU works by using a multimeter?

I haven't tried it out on my Craftsman tools yet because I didn't want to risk damaging them if I was wrong, and I don't own a multimeter so I haven't checked to see if the PSU works or not, but it worked the last time it was plugged into the laptop. I'll have to try what holding the trigger in before I plug it in and/or hook it up to my Craftsman drill. Do you think the fact that I was using a 19v PSU on an 18v drill could have anything to do with it?

you may have overloaded the power supply and activated its internal protection try to connect it to the drill to the power supply in series with a high power electrical heating appliance (without motors) like kettle or radiator. does the motor spin or show intension to spin ? maybe a really big capacitor in parallel with the power supply output can help

an extra volt shouldn't do much of anything to harm a motor. Do you know if it was fused? (has a fuse somewhere that could have blown).

Search instructables for cordless tools, a few have converted cordless to corded. Good luck.