Buck converter to run power tools off ebike "36v" LiFePO4 battery?

kg6gfq

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I have an old cordless drill (and possibly some other tools) that have no batteries. I have a nice "36v" 24Ah LiFePO4 battery (voltage at full charge actually ~43.8V). What converter can I use to step that down to 18V for my drill? I'd especially like an adjustable-output converter with a display that shows output voltage so I can power other things with it.

So far everything I'm finding is rated for up to 40V (like this). Can I just use that? Will it be ok with an occasional input voltage above 40V? Or is there a better option that I just haven't found yet?

Thanks!
 
I've had some experience with DC DC buck boost converters from feebay. Most of them have an inconsistent output voltage that will wander a bit if the converter goes above slightly warm.

If you do manage to find one with a regulated output, I'd recommend shooting for twice the amps that your cordless drill will need. When Aliexpress says 12a max what they really mean is more like 8a max and you can briefly expect 10a but not sustained. Which seems to be the case with lots of Chinese made electronics these days.

Like this one: https://www.aliexpress.com/i/32956137689.html

*Just had a look at the DC converter you linked. I doubt that 20 watts would be enough. Maybe a wall wart would do the job for cheaper? https://www.google.com/search?q=18v+drill+power+supply
 
No, you need one rated for at least 50V, higher if cheap chinese

And you need to measure the maximum Watts the drill pulls, like going through heavy, dried hardwood with the biggest sized bit.

The DCDC should be rated at least double that, 4-5x if cheap chinese.

Probably cheaper to just buy new batt packs at home depot
 
Or just use tools rated for 110v AC. They almost all run on DC though not all with enough power for the job.
 
So you’re looking for a way to convert your cordless drill to corded, but with a bunch of other components? You may need a backpack.
 
You could break down the old Lifepo4 battery if you are not using it for anything else.

I think that a 36v lifepo4 is 11s? If you break it down into a 6s and 4s battery. So you would then have a 19v battery for your tool and a 12v battery you can use for something else. Lots of stuff likes 12v.
 
I had a similar idea involving a 13s battery that I've made for a trimmer/brushcutter which i carry in a backpack when i cut the grass.
This is a 13s 1kWh battery and I want to also use it with the dewalt 54V chainsaw.
That chainsaw accepts a 15s battery, so I thought that I'll use two boost converters in parallel which would produce 54V and 40A.
The boost converters would be in a casing similar to a dewalt battery and I would just slide it in the chainsaw like a normal battery.
https://www.thingiverse.com/thing:4789309

The runtime would be much bigger because of a bigger capacity of my battery and I would not have to buy an aditional
batteries or an additional charger.
I have a few concernes though, what's happening with the voltage on the output terminals of the boost converters as
the battery voltage goes down? And do I need some special electronics so that the chainsaw is fooled into thinking
that this is a normal battery?
 
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