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I have a few (working) 18V batteries (Makita, LXT) and I would like to be able to power some AC (220V) power tools with them. Many of the AC power tools have electronic control and simply applying DC to them would not achieve anything good, probably.

Is it feasible to connect these batteries (series, parallel) and use an inverter to output a decent 220V AC output? Is there some other way to use them to power existing AC power tools?

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Almost certainly not. Virtually all inverters are set up for 12/24/48V input, none of which you are going to get from stacking 18V batteries. Even if you did find one suited for the odd voltage input, the capacity of portable power tool batteries will quickly be exhausted, even if you have "a few" - and paralleling those few can cause problems with the batteries - the weakest one gets lower than the others and the others try to charge it - depending where the battery protection circuitry is, you either kill the battery as the internal protection goes off, or you get battery flambe (likely just the boring dead case with a major brand like Makita.)

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It's possible but not as easy as stringing them into an inverter. DeWalt makes a device for this purpose in their 20v line.

https://www.dewalt.com/products/gear-and-equipment/generators-and-portable-power/1800-watt-portable-power-station-and-simultaneous-battery-charger/dcb1800b

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    Interesting concept. But extremely limited. With the max of 4 x 20V x 3 Ah batteries, that is equivalent to 240 Wh. Which at a continuous 1800W output would only last 8 minutes. And that's not counting conversion losses. Which means realistically you either have to bring a lot of spare batteries or you use this to run mostly auxiliary devices that require AC power but don't actually use very much of that power, or very short usage time devices. – manassehkatz-Moving 2 Codidact May 9 '19 at 14:10
  • This is exactly what I want, only for Makita :((( The 8 minutes max duration - at 1800 W - would more than suffice me. – Andrei Rînea May 9 '19 at 21:02
  • Not like any manufacturer would warrant the setup, but people have hacked together adapters that put a makita battery on a dewalt tool. Check that you've got a Euro version of the dc1800, though. This one puts out 120v AC. – Aloysius Defenestrate May 10 '19 at 3:17
  • Thanks! I will probably resort to using a 12V auto battery with a commercial pure sine wave inverter attached to it. – Andrei Rînea May 10 '19 at 10:07
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Forget the inverter. 99% of portable power tools use what's called a "Universal Motor" which is actually a DC motor that does its own internal rectifying of an AC input. So you can feed DC directly into that type of motor. If it is a 230V rated tool, you need for the voltage to be approx. 330VDC so with 18V batteries, that is 19 of them in series. Do you have that many?

If you were not referring to portable power tools, that will not work, bench power tools usually use traditional AC Induction Motors.

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I'm perfectly fearless about proposing bold solutions... but this is NOT one yyou want to pursue. Unless you aim to rewind the motors, stacking batteries means you'd be pumping 230ish volts DC into the motor.

DC at such voltages is like the honey badger of electricity: rather badly behaved stuff. It will more seriously shock you. And if it starts arcing, it can't be bargained with, it can't be reasoned with, it doesn't feel pity, or remorse, or fear, and it absolutely will not stop, ever, until the fire is engaged enough to burn up the contacts.

That URL is only 600 volts, and you're already at 230. Danger Will Robinson!

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  • I understand the risks and I will abandon this idea. I will resort to using a 12V auto battery with a commercial pure sine wave inverter attached to it. Thank you! – Andrei Rînea May 10 '19 at 10:07

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