Milwaukee custom charger for work ute

Thread Starter


Joined Mar 19, 2023
Hey guys,

I have looked everywhere and haven’t found what I want. I am trying to make a charge station out of the Milwaukee battery holders in my work ute. I know I won’t be able to charge all my batteries at once, but I’m trying to find a way I can charge Atleast 6 batteries. I have toyed with the idea ofbutchering a milwaukee 6 bay sequential charger and wiring it in. Has anyone tried this or know of ways I may be able to achieve this. We’re always on the road and charging one battery at a time while travelling can be annoying.

I have attached photos of my batteries mounted to my tool box. And the adapter style I’m looking at using. I want to be able to charge Both M12 and M18. I was looking at the M1418C6 and the M12C4 to run to inverters and use the boards out of them to wire them in. But I feel like there could be an easier way.



Joined Jan 27, 2019
Welcome to AAC.

Your best bet is to modify an existing charger. The sophistication of modern tool battery chargers is very high and reproducing the circuitry is not trivial. Rather than use an inverter, you might find you can use the 13.8V supply from the truck with a boot converter to provide the DC voltage needed on the board after its own power supply.

In any case, starting with a working charger is your best bet.


Joined Sep 2, 2020
I've tried modifying the 48-59-1812 (M18™ & M12™ Multi-Voltage Charger) to run off DC - but to no avail. The charger is frankly "weird". It tells transformer and voltage regulators to supply both a "about 11.1 - 13" and a "about 18 - 23" volt supply, but ramps it up when a battery is attached. So, it's weird and not easily amenable to just hooking up 1 buck and 1 boost converter to the appropriate rails. I could get M12 to charge by jacking the "about 11.1 - 13" to 13V, but it would err out after charging. Never could get M18 to charge. The battery "thinks" it is charging, it shows an indicator light on the battery, and even blinks it - but no power goes in to the battery.

So, I've decided to just get a portable (3rd party) charger from AliExpress, and then use a boost circuit with CC/CV (i.e. current-limited) boost circuit to power it.
This store has the same charger with different pricing and shipping options, so depending on how many you are purchasing, one or the other will total to less money:

The downside is that those chargers are 1A (the standard Multi-Voltage Charger is 3A). My portable (3rd party) charger was just ordered today, so it will take a few weeks to arrive. I doubt I can just supply 3A - its design looks similar to my Worx charger, and if I put more than 1A in, the tiny MOSFET in the Worx charger will burn up. I suspect this to be be the case with the 3rd party M18 charger - so only buy it if you're happy with fairly slow charging. When it arrives I'll test it and maybe modify it too.