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DIY Milwaukee M12 USB charger


AntleredRuin

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So I have an unsanctioned 'hack' for a USB phone charger from a Milwaukee M12 battery. 

An official M12 USB phone charger only costs around $30, comes with a warranty, etc, so this hack probably isn't worth it, but it's still fun. It's also a more customizable, albeit a bit ugly.

This hack cost me all of $5, not including the battery.

 

Basic disclaimer: I am not responsible for any injury, damage, etc, that may come from attempting this 'hack'.

 

Take a 12v cigarette lighter socket, like this:

1025181326.jpg

https://www.amazon.com/Cigarette-Lighter-Adapter-Motorcycle-Scooter/dp/B07B4QBPPD/ref=sr_1_2_sspa?ie=UTF8&qid=1540492162&sr=8-2-spons&keywords=12v+outlet&psc=1

(I got mine for $5 from a local hobby shop with a bunch of change that was jangling around in my cupholder, so I'd consider it free)

 

By absolute luck (or maybe Milwaukee designed it that way on purpose?) the 2 male spade terminals on the 12v socket fit perfectly into the battery's female terminals. Like they were made for each other. I can't guarantee that all sockets will fit, but the one I have linked will, based on the pictures (it matches mine perfectly).

 

Then, plug a 12v car adapter phone charger into the socket, and voila, you have a portable power pack!

 

1025181325a.jpg

 

Make sure you have the polarity of the spade terminals right (positive to positive and negative to negative). You won't hurt the socket if the polarity is backwards, but you will fry the phone charger (and possibly hurt the battery). The socket shows the polarity clearly, and the batteries show it in very tiny print under the female terminals. 

 

1025181327.jpg

1025181327b.jpg

 

The 12v car adapter is designed to take 12v (+ or - 5%) and convert it to 5v USB. I know that some can withstand up to 24v input, but obviously, the M12 batteries are 12v, so there you go.

 

You can also use a 12v USB adapter like this if you wanna be really fancy:

https://www.amazon.com/Ginsco-Charger-Socket-Outlet-2-1A(4-2A)/dp/B01N6S2SNM/ref=sr_1_3?ie=UTF8&qid=1540493108&sr=8-3&keywords=USB+12v+outlet

 

 

The 12v car adapter should still put out the appropriate amperage it's rated for (1.0, 2.1, 2.4, etc), but keep in mind that while higher amperage will charge faster, it will obviously drain the M12 battery faster, too. I have no idea if the 'smart charge' on the phone will sense when it's done and cut the voltage, so once it gets to 100%, I'd recommend unplugging it.

The 3 'smart tabs' on the front of the battery are unused, and Milwaukee uses those to communicate with the tool to avoid over/under voltage scenarios, undercharging batteries, etc.

So this is effectively a DUMB power pack, and doesn't know when to stop charging.

 

I was able to charge my LG G4 from 30ish% to 100% twice on one 2ah M12 battery, so it works pretty well, especially in a bind. The LG G4 comes with a 3000mah battery. The math is not exact, obviously, but it's close enough. Any LEDs on the charger or socket will also sap the power, so keep that in mind as well.

I keep 2 2ah, 1 4ah, and 1 6 ah batteries in my car at all times, and often can't sit near an outlet when I work, so this saves me a lot (though I still may buy an official adapter).

 

The batteries don't come with a fuel gauge built in, as we know, so I'd suggest keeping an M12 tool nearby to check the battery every once in a while to not discharge it completely.

 

There are also a bunch of USB powered devices, such as fans or lights, that this will work on as well!

 

 

 

 

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