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Charge 24v power tool battery in a 12v car

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TaDa

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I want to buy a 24v impact driver - well a man has 'needs' :)

But I want to be able to charge it in my car.

Any suggestions about how I should go about this would be appreciated.

There are lead acid and lithium battery powered drivers available.
I'd prefer lithium because they're lighter but are there any gotchas for charging lithium power tool batteries I should worry about?

Thanks
 
The easiest way is probably to use the mains charger that comes with the tool and use a 12V to 120VAC or 240VAC (as needed) inverter to power the charger.

There are significant differences between charging a lead acid and a lithium battery, but if you use the tool charger designed for the battery, you should have no problems.
 
I've never been a great fan of using inverters in this way - I see the point for powering things that are fundamentally mains (washing machines, lighting circuits maybe) but to then un-invert the power to around where I started just seems wrong :)

Hmm - I guess the charger could be doing some triac trickery.

Aren't inverters inherently lossy? - not to mention the power lost in bringing it all back down to 24v.

If charging the tool requires me to use clever circuitry from the charger then I think I'd rather hack about with the charger and change that to run in "mains" or "lower voltage DC" modes.

So, I guess what I'm after is a bullet proof way of changing 12v car to 24v+ DC - is this where I start looking at boost circuits?
 
Well, you could roll your own DC voltage boost circuit, but they are also inherently noise since they involve switching regulator circuits. Then you would have to hack the charger to operate from the switching regulator DC output. All in all a lot of work just to avoid doing something that subjectively "just seems wrong". In engineering sometimes it's better to go with the simplest solution and not the most elegant.

Using an inverter may not be the neatest solution, but it's the easiest and should work. Unless you are very concerned about efficiency, that should be tolerable also. Bringing the AC voltage back down to 24V usually involves a transformer in the charger, which is quite efficient. Use an inverter not much larger than you need and check its no load current, which will give you an idea of its efficiency (the charger likely doesn't take much power so you should be able to use a small inverter).
 
There is no other way to convert a DC voltage to a higher voltage without switching. So EVERY possible solution available to you will be an inverter of one design or another.
 
lol. Okay, not every solution, but every practical solution =)
 
I 'listened' to you all and thought about it a bit more and I agree - the pragmatic solution is to use an inverter.
Doubly so now I see how cheap they can be on ebay :)
It still seems wrong - but the hours of my life saved outweigh that.

Thanks everyone
 
Some power tool battery chargers will be destroyed when used on the cheap modified sine wave inverters. You might want to research if your charger is modified sine wave friendly. A sine wave inverter is the best choice but are more expensive.

creakndale
 
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