Heavy Metal Power Bank Uses Tool Batteries

At one time or another, most of us have seen a gadget for sale and thought we could build something similar for cheaper. Of course, we’re almost always wrong. Not about being able to build it, mind you. But when you add up the cost of the materials, the tool or two you almost inevitably end up buying, and the time spent chasing perfection, you’re lucky if you haven’t doubled the original price.

We’re not sure how much money [Taylor Hay] ended up saving by building his own portable power bank. But we do know it’s a gorgeous piece of hardware that’s certainly built far better than the average consumer gadget. The CNC-cut aluminum side panels look like something pulled out of a tank, and while we know some might balk at the 3D printed internal frame, we’re confident you could use this thing as an impromptu step stool without a problem.

Inside there’s 150 watt 240 VAC inverter, complete with a temperature-controlled fan to keep it cool under load. There are also four USB ports providing 2.1 A each, a standard 12 VDC accessory port, and a LED display that shows battery voltage and current being drawn. Rather than come up with his own battery pack, [Taylor] used a 3D printed interface that accepts an 18 V Milwaukee cordless tool battery. Naturally, the design could be adapted to take another brand’s cells if you were so inclined.

Around these parts, we know that a good project doesn’t have to be cheaper or even more practical than what’s already on the market. There’s an inherent value in building something exactly the way you want it that you simply can’t put a monetary price on.

17 thoughts on “Heavy Metal Power Bank Uses Tool Batteries

  1. Utilizing powertool battery packs in the DIY sector is not really a new thing, and for DIY projects it’s actually quite fun to use those bricks. After all, if you have them, why not use them? The one concern I do have with this little project is undervoltage protection. The battery protection circuit on Milwaukee M18 batteries really only is semi-intelligent at best. It monitors battery pack temperature, charge/discharge cycles, voltage levels and so on… but that’s it, it only MONITORS them and does the balancing. It reports back to the tool via a proprietary protocol, and if you simply connect the positive and negative terminals of the pack to your DIY project, you can and WILL deep-discharge the brick, after which the charger will refuse to charge it.

    So, good idea to implement your own voltage monitor that cuts off your device when voltage drops below around 13-14V pack voltage.

    1. Great thoughts Thomas! Version two is likely going to have a voltage divider to close a relay when voltage is above 15v, but building that circuit was a bit out of my specialty zone :) I don’t want to limit the available current too much by using a fet, any thoughts on that?

      1. Of the dozens of flashlights, bluetooth speakers, and jobsite boombox radios over the decades of Ryobi 18V, I’ve found some tiny switching power supply modules small enough to wedge into a corner of the largest plastic cases. There’s one specific jobsite lamp from the 00s or 10s that has a flat spot long enough for an Anderson Power Pole distribution panel and it looks pretty good.

        Of course its almost cheating that Ryobi sells a 150 watt inverter, so “building an inverter” amounts to ordering and opening a cardboard box. But there’s still some engineering magic in making a 13.8 volt power distribution panel with low enough interference output to run ham radio equipment.

        Or in summary, yeah ryobi is where its at for ham radio / EE type hackery.

  2. Thanks for the feature! Total cost was about $8 worth of PLA filament, everything else was scrapped from a broken inverter or my parts box. The USB sockets / amp meter were free from work, but can be had for $5 on AliExpress :)

        1. Surely you don’t think HaD makes these people’s project videos, do you? Or are you suggesting that the site shouldn’t run a project if the title of their YouTube video isn’t up to snuff?

  3. I have been using car lithium ion jump pack to provide portable power to run my camera strobes on location. Specifically the GOOLOO brand ones. Unlike a lot of the jump packs that have 3 cells in series these have 4 with a full charge voltage of 15.4v and since most 12v inverters seem to have a max input of 15.6v it works out pretty perfect. And the inverter auto shutdown puts in just above the minimum cell discharged voltage. I am running a 600w samlex pure sine inverter with it and it runs three 500w/s lights without any problem.

    I use this one and it’s larger 4000A brother. Though they seem to be out of stock.


    I use this to connect to the inverter, that black blob is a shottky diode array to prevent current flowing back to the battery when jumping a car.


    And these packs work great for jumpstarting cars.

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