Electric Chainsaw Teardown

An electric chainsaw with its case removed

For his Beyond Unboxing series, [Charles] tore apart a Ryobi cordless chainsaw to get a better look at how this battery powered tool works.

Inside he found a three-phase motor and controller. This motor looks like it could be useful in other projects since it has a standard shaft. The battery pack was popped open to reveal a set of LG Chem 21865 cells, and some management hardware.

With all the parts liberated from the original enclosure, [Charles] set up the motor, controller, and battery on the bench. With a scope connected, some characterization of the motor could be done. A load was applied by grabbing the spinning shaft with welding gloves. [Charles] admits that this isn’t the safest way to test a motor.

While it is a very fast motor, the cut-in speed was found to be rather low. That means it can’t start a vehicle from a stop, but could be useful on e-bikes or scooters which are push started.

This chainsaw a $200 motor, controller, and battery set that could be the basis of a DIY scooter. It sounds great too, as the video after the break demonstrates.

[Thanks to Dane for the tip!]

Comments

  1. Sean says:

    Controller controller? Yo dawg I heard you liked controllers…..

  2. Rollicks says:

    +1 for not being about quadcopters.
    -1 for hurting an innocent chainsaw.

  3. henry says:

    It’s a shame it doesn’t come with a conventional sprocket so you could use it out of the box with a bike chain.

  4. chuck says:

    Why does an electric chainsaw have a tank?

  5. Robert says:

    Does this thing even have an mechanical chain brake? Guess it wouldn’t be legal in Germany.

    • Adobe/Flash hater says:

      I’m only assuming here, But I figure it may use electronic breaking.
      I imagine it would be difficult or imposible to get a saw on the market without some manner of breaking built in.
      Does the controller appear to have an accelerometer
      in it? If so, that could be a anti-kickback trigger
      by switching the circuit to “E-brake” the motor.

    • henry says:

      I’d say so. My cheap electric chainsaw (corded) has one built in.

    • churlz says:

      I certainly didn’t notice any mechanical braking. It stops pretty fast after you let go though.

  6. Dr_Lion says:

    I was hopping to see a moded cordless chainsaw to be usable directly connected to a car battery. Since a eletric one is cheaper, requires less maintenance, and is pretty noiseless compared to a fuel one.

    But this might be the begining..

  7. Concerned says:

    Dear HackADay,

    Your brand is being damaged by shoddy editing. Please institute at least a second set of eyes on your articles before publishing.

    Sincerely,
    A Concerned reader.

  8. matt says:
  9. strevo says:
    • Randy says:

      The 18V line does not have the same motor

      • Randy says:

        however, that looks like the same model, minus the battery and charger so maybe good for hacking?

        • SOI Sentinel says:

          Don’t know. the batteryless version is a 16″ chainsaw is identical ($130) this little 12″ one ($99) we won’t know till someone tears it apart.

        • strevo says:

          Considering ZERO specs about that, yay, who knows. if it’s anything like the others,

          A 12″ vs 14″ would require the same speed, the only real difference being the size of a log it can cut – and a larger log might need more torque as more teeth will be cutting at any given moment – so it’s possible the 12″ has less torque.

          BUT cost analysis suggests its MUCH cheaper to make both models with the exact same guts. Which I’m betting on… I’ll be back with one… lol, give me a week, ordering it online.

        • colecoman1982 says:

          Considering that it’s hard to find any reference to it on Ryobi’s official site; is being sold by Home Depot; is missing the battery; and is weirdly only 2″ shorter, my guess is that this is a an example of what I’d call a “semi-knockoff” where a big box retailer (in this case, Home Depot) manages to convince a big name brand of things like power tools or appliances to make a special, modified, version of one of their products with some corners cut in the quality/features department.

          Normally, I’d run away from something like this as fast as possible because, in my experience, the original manufacturers seem to think that they can just not bother supporting these kinds of orphaned products entirely (often, to the point of not even allowing ANY reference to their existence on their official web site). However in this case, because the intent is to scrap the tools for it’s parts instead of relying on it’s over-all build quality to ensure long-term reliability, it might actually be an ideal situation if it means getting the same/similar motor and controller for half the price. Of course, we won’t know if they cheaped out on those parts until someone actually gets one and takes it apart.

          • colecoman1982 says:

            Now that I think about it a little more, I think a better term might be “self-knockoff”.

          • targetdrone says:

            Ryobi is owned by the same company that owns Milwaukee tools and Hoover vacuum cleaners. Ryobi tools are sold exclusively through the Home Depot, and are almost (but not quite) a “house brand”. They can’t be a knockoff, but they can have different price points for different classes of tools.

          • Chrome Dragon says:

            That’s a Mk.1 product, not a knockoff. The Mk. 2 is when they switched to the brushless motor, and it has a substantially higher cut capacity, so I’d wager the old one’s half as powerful.

    • Chrontius says:

      It’s absolutely not the same motor/controller set. That’s the first 40v tool, this article’s about the second generation, and neither is a knockoff.

    • Chrome Dragon says:

      It’s not.

  10. strevo says:
  11. Rob says:

    Fantastic teardown, I’d love to see more of these on HAD!

    A question I’ve long had regarding battery operated tools… when the battery has ceased to hold a meaningful charge and you’ve discovered that it, like every other battery pack ever made, is no longer available (because apparently NO ONE can bother to stick to the same pack type for more than a model or two before changing it and rendering the old tools obsolete), what’s involved in doing a mains voltage / corded conversion?

    For example, I’ve got an 18v weed whacker type tool, the Ni-Cad battery pack is getting close to being crapped out (it has lived much longer than I would have ever expected), and while I could rebuild it manually I’d just as well not spend that $40 or so to do so. I’d hope that I could just drop a 3 or 4 amp (the mAh/time equation points to a max power draw a little shy of 3A) 18v wall wart into the old battery cavity, fake out the thermistor line, and carry a mains cord behind me (the yard is pretty small, but I’d rather to the voltage conversion at the tool rather than at the outlet… the voltage losses at 18v would add up). However, I’m wondering if I might need some sort of current regulation so the motor doesn’t burn out. I would assume that the 18v battery pack’s internal resistance performs that function but that a simple wall wart would not do so? Maybe I’m overthinking this, I dunno. I’m loathe to burn out the tool just to find out, as the weeds aren’t going to go on holiday for my convenience.

    Has anyone else ever done such a conversion? Has such a conversion ever been featured here on HAD? I’d be interested to learn more.

    • HalfNormal says:
    • strevo says:

      you’ll probably need a MUCH higher amperage wallwart, which would make that $40 battery completely worth it.

      • Rob says:

        you’ve got a point there… I think I was working out the mains side draw when I did the calculation. It might just be more cost effective to buy the replacement cells and rebuild the battery. Looks like a charging cycle on the existing battery is costing me all of a penny or two (thanks, Kill-A-Watt!), so charging a fully-chargeable pack would double that (at most). Given those figures, it would probably take me a very long time to recoup the costs of such a conversion. Oh well. If the tool itself ever dies (it’s a Craftsman rebrand of a Worx model… how long can it live?) I’m going to go with a corded model. I’ve learned my lesson. Based on the writeup in Kevin Kelly’s “Cool Tools” guide (http://www.amazon.com/dp/1940689007/?tag=bestbookchoices-20), I would go for the recommended Stihl FSE 60… for now though, rebuilding the battery pack is still cheaper.

    • HC says:

      In my experience, aside from screwdrivers, battery powered tools are never worth the massive hassle. An AC-powered tool and an extension cord on a spool gets the job done without time limits or replacement parts.

      • Jason B says:

        Cordless drills and cordless impact guns are worth their weight in gold when paired with a Li ion pack,

      • denis says:

        you obviously dont work with them on a daily basis then, my cordless drill, impact gun and reprocriating saw out do any corded or pneumatic version i have owned previously, both in power and handy-ness. Modern battery power tools (quality ones!) are amasing.

        • SawedUp says:

          I couldn’t disagree more. I’ve never seen a cordless tool that could match power output with a conventional corded (or pneumatic / gas powered) tool of any variety. They have come a long way and are certainly handy for lighter duty tasks, but I’d prefer to spend less on a quality corded tool that will still perform after sitting on a shelf for a few years. To me a tools like rechargeable chain saws, string trimmers and angle grinders are a joke. That being said, that 3 phase motor and controller look pretty sweet and would be perfect for any number of non-chainsaw related projects.

    • Jedi says:

      methinks you could rewind a MOT (Microwave Oven Transformer) and get some heavy duty diodes and caps, although the MOT would add a few pounds.

    • Chrome Dragon says:

      Ryobi is pretty darn good about sticking to one electrical interface – they’ve been using the same 18v electrical standard and form factor since the mid-nineties. And they’re on the fifth generation of their “One+” battery. If the 40v form factor has that kind of staying power, it’ll be available in a decade or more.

      Since they have a second generation of all their 40v tools, I consider Ryobi to be logistically safe to invest in.

  12. Jedi says:

    handy dandy e-bike conversion kit

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