Power Tool Packs Make A Portable Powerhouse

The revolution in portable and cordless appliances has meant that we now own far fewer mains-powered gadgets than we might once have done, but it hasn’t entirely banished the old AC outlet from our lives. Particularly when away from a mains supply it can be especially annoying, but now instead of a generator there’s the option of an inverter. [Thijs Koppen] has made a very neat all-in-one mains power station in a plastic flight case using the ubiquitous and handy standardized Makita power tool packs.

From one perspective this is a simple enough build, because wiring a battery to an inverter isn’t the most difficult of tasks. But he’s designed his own 3D printed Makita battery receptacles which should be of interest to plenty of readers, and with three packs in series he’s sourced an unusual 72 volt inverter to supply mains. The photo of him charging a Tesla with the result is probably more for show than practicality though.

We’ve featured quite a lot of cordless tool battery hacks over the years as their ready availability and quick interchangeability is attractive. If you ever fancy engineering your own mounting, we’ve taken a look at someone doing just that.

15 thoughts on “Power Tool Packs Make A Portable Powerhouse

  1. It would be a good idea to add reverse diodes across each pack. Otherwise if the pack protection circuit cuts out, it will see the voltage from rest of the batteries in negative direction, which it might not tolerate.

    1. Stumbled over a pretty similar problem when I combined two PSUs, a 20v Dell and a 32v HP, to test a PoE switch. Instead of powering the switch the Dell’s protection circuits constantly kicked in until I added a diode.

    2. When researching this project, I found that the battery cut-out is actually part of the tool, being reported through a third pin on the terminal. One of the improvements I want to make is a separate PCB to monitor individual pack voltage and cut power when one of the packs gets below a set state-of-charge. Thanks for the tip tho, might come in useful for a different project!

  2. Large batteries around the house should have uses during power outages. For now the proprietary connectors and different voltages keep them from being as interchangeable as 12v car batteries or old D cells.
    It took a few adapter cables and a specialized 60v inverter, but now my e-bike batteries can give me 120V AC and USB-C PD when either the power is out or I need juice away from an outlet.

  3. So, those Makitas cost around $1500 per kWh. LFP batteries can be had for much less than half that. If you’re looking to tote more than a fraction of a kWh, power tool batteries start looking kind of foolish. Though they *are* good for high peak power, if all you need is a few kilowatt-minutes.

    1. Power tool battery are also good for durability – they have to survive a building site so are physically rugged, and generally seem to have very solid BMS built in.
      Also of a sensible size and power density that the concept of hotswapping multiple powertool battery for 100% uptime potential may make them a better choice as the connector is done for you.

      So yeah this to me doesn’t make sense for most folks as it isn’t cost effective unless you actually have a heap of whichever powertool brand battery you use. In which case it does give you the flexibility in how you use them for no extra cost on the battery side – as long as you don’t want both this and your tools at once you don’t need any new battery at all.

    1. It does a few different jobs.
      The top part of the cable detaches and you can swap plugs based on what type of outlet you are nearby. There is a thermistor to check for overheating of the plug due to bad cabling. Relays are in the box as well to make sure the cable isn’t energized until plugged into the car. There’s also some communication logic to tell the car what the maximum current the adapter can support based on the plug you have attached.
      LEDs on the box indicate charge state at a glance and generic errors.
      Not sure if there’s any other functionality I’m missing.

      No cellular or license key to my knowledge.
      You can look up Tesla Mobile Adapter v2 for more info.

      1. The Nissan Leaf has a similar device for its plug-in charging cable. Probably does most of the same things as it supports 120v and 220v outlets, and it refuses to work on some extension cords.

  4. Sounds like a good idea and it has merit, though to be honest, in the case of a blackout, my tool battery packs are either in the bag with the tool or on the charger, and all of that is in the back room. I do have bedside lights in both bedrooms and one in the middle room downstairs on UPS’s though. No need to go groping around in a dark room rounding batteries up or dealing with lamps in.

    Now, in the case of power past where you want to run it. I have a box I built, the juice box, that has a coupe of 24AH gell cells and an inverter in it. That works well, but to be honest, it is not unlimited power and if you are running power tools, you do not get a lot of run time. I have a 1.2KW 2 cycle generator and that weighs about the same and that can supply more power, though you do have to wait for the tool to spin up, and much longer run time, and easy to add more gas.

    I have a wagon for to tote either one of them any distance. I also have a little 3 gallon air compressor and a battery charger that I can toss on the wagon if I need to blow up a tire or have a dead battery on something far from the shop. The wagon also will tote and power my electric pole saw, and that is a nice combination.

    1. I’ve thought about getting one of those tiny generators, and making a self-propelled version of your wagon. I could use an angle grinder with a sprocket to drive it, and a variac for speed control. Could be fun.

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