Electric Chainsaw Question

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#1

Thanks for your reply. I am new and so far I’ve been impressed.

I want to examine another topic that relates to processing wood: operating an electric chainsaw in the field from battery power.

To introduce this topic, I will share with you a brief story from my personal life: Recently, strong winds here pushed over two more trees in my yard and I was able to harvest some great pieces of wood.

Please see photo of my gas chainsaw equipment:

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As you can see, I am able to mill a few boards with a chainsaw cutting guide.
The problem is that when operating the chainsaw, exhaust gas is directed towards my face.

My goal is to use an electric chainsaw because it will be quieter, and no exhaust gases. The saw that I have is 120V, 1500W, and plastic case and I would like to use it in the field off 12V battery power.

It is my opportunity to open this topic to discussion related to running electric chainsaw in the field with one caviat: Instead of running the electric motor in the chainsaw at 50/60hz as would be common in US or EU, run the chainsaw at ~80hz to cut faster.

If the 1500W saw can be run twice as fast (100hz) , it can reach ~4hp which is comparable in power to a gas saw.

At this time, I am not interested in three phase motors because they are expensive. I am hoping to modify a regular 12V inverter to speed up the oscillator. I am happy to do some digging on the topic so please drop hints. Thanks, and have a nice day.

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#2

Hi Joe, i think that sounds like a good idea, this was done in the chainsaws early days, Homelite built a gasoline gemerator/electrical chainsaw that was made to be used together, if i remember correctly it was a small three phase electric motor, running at about 180hz, this was to get the revs up, and better power transfer.
I think you could maybe find some e-bike motors cheap that is three phase, use one as a generator, one as motor on the chainsaw?
This would probably give good power and rev’s.
Not something wrong with your original idea, just some input/ideas from me :blush:

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#3

Sorry, more dumb ideas from me, (im a chainsaw maniac) modifying a inverter should be no trouble, i think, but how about controlling the oscillator circuit, and voltage from the chainsaw handle? By some tiny “feedback” wires, not needed, i know, but will give good control over the saw, and save some on the batteries charge.

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#4

The electric chainsaws we have had, that I have taken apart, have had universal motors, motors with brushes and a wound field like a big sewing machine motor. They will run on AC or DC, but on DC the switches might not last very long. Anyway, line frequency won’t affect the speed very much for this type of motor, but voltage will. Adjusting the voltage of an inverter probably wouldn’t be to difficult, until you exceed the voltage rating of capacitors and/or MOSFETs, at which point the inverter will be dead. But if you want twice the speed, 240 volt inverters are available. You could reduce their voltage without much risk. At some point the saw will give up.

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#5

The battery electric chainsaws are typically brushless DC motors. I would personally be more inclined to hack a ‘fake battery’ because their biggest issue is battery life. However, I believe there is a communication protocol between most tools and the battery that would have to be faked so it isn’t as easy as just hooking up a 80v power supply to the tool.

I don’t know what would happen if you took apart the battery, got rid of all the battteries and just connected the power supply leads to where the battery leads go… that might actually work if the voltages were matched right…

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#7

You can convert the older power tools. I have done it before and have yet another project where I need to convert a cheapo harbor freight drill. The newer ones usually with lithium have a communication protocol to help prevent fires when the lithium batteries internally short which can happen for various reasons (physical damage/dropping, overheating, old age/dendrites, etc). The milwaukee’s 18v series most likely has something.

But here is someone trying to hack the greenworks protocol, and I think Dewalt uses many of the same electronics.

While it is a good video and I watched it a few times, it might be slightly outdated as manufacturers keep refining their products.

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#8

That was the video that made my mind up to buy the Echo, most bang for the bucks. I have used it a lot, and have no regrets.

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#9

Apparently a couple of folks have looked at this and it might be easier to get the milwaukees to work with a power supply. The protocol is actually pretty weak between the battery and tool, but the charging protocol (different video) is slightly more complex.

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#10

I chose the Echo because of the Project Farm review but also because of the price. The comparable Stihl was over twice as much money and I didn’t have a local store selling the Husky. I am always willing to pay a little more than Amazon might charge so I can take it back to the place of purchase if it screws up. Both Stihl and Echo can be serviced locally here without having to jump through to many hoops. I"ve said before that I don’t consider this to be one of my first tier saws and I never cut logs with it. Just limbs and branches and the idea that after three years the battery may be losing some life is a bit troubling. As I also said the battery was $170. I have to try and calculate how much gas and mix oil I haven’t had to buy for the battery saw and see how much that offsets the replacement battery cost. As far as weight considerations go, when I can no longer work with a 12 pound tool just cover me with compost and plant tomatoes on me.

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#11

I got the greenworks because of reviews and price, and a few projects that needed to get done which covered the cost of the saw. I don’t know if it will save as much gas + 2 cycle oil as the battery cost. It is more convenient, and very quiet so you don’t attract attention from snooping neighbors.

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#12

Good evening,

Thanks for everyone’s kind responses. I have been considering what you wrote meanwhile this winter storm continues outside. Here is a picture from before the snow fell of my chainsaw skid built from the tress I cut into 3-3/4" slabs.

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Those are 10" pneumatic tires; they roll across the lawn and driveway well. The hooks are plywood. I push it from the left side.

I realize I don’t know who I’m communicating with, and they don’t know me.
I would like to take this opportunity to introduce myself with this message I wrote in 2019 around this time of year : My Greeting

TLDR: I did used to be computer progammer, but i found it boring on the computer and most of my colleague in IT are gaining weight and losing hair. So, I decided to change my carrier.

From the discussion, I understood that my own idea of electric-motor was oversimplified. I was thinking, in theroy, of the simplest dynamo: the permanent magnet synchronous motor (AKA AC synchronus) inside of my chainsaw. Synchronous motor - Wikipedia

However, today’s tools are made from motors of many designations:

Permanent Magnet Motors vs Induction motors
Asynchronous vs Synchronous
Brushed vs Brushless
AC/DC And, hybrid types exist today such as the Universal Motor.

That said, all types of electric motors produced share these components; they are the basic elements of a dynamo:

  • Stator - Stationary part of the motor; the housing
  • Rotor - The moving part of the motor
  • Armature - The windings of insulated copper wire around an iron core

Where they differ in designation is with presence of:
Commutator - rotary electrical switch that uses carbon brushes
And, location of the armature. Sometimes it’s in the rotor, sometimes it’s stationary (in stator).

Before we look at some contemporary electric motor designs lets consider this theroy:

At any moment of time, the force applied by an electric motor is the result of a magnetic force created by a current of electricity in a magnetic field. At that moment of time, the electric current can have only one direction. Thus, it could be said that the action of all electric motors are driven by direct current.

However, in order to keep the motor rotating through time the current must reverse. Thus, it should also be said that all electric motors producing rotation and torque rely on changing polarity of an electromagnet via Alternating Current (AC) to rotate.

In Summary, the force is produced by direct current in magnetic field. The rotation is produced by changing polarity of an electro-magnet via an alternating current. It is true for all motors that Force exists with out respect to time, but speed as rotation is driven by alternation of current at a given frequency. In that sense, I am going to say that all motors are AC motors, because they rotate as described.

So, what then is a DC motor? Or a Universal Motor?
It’s a regular electric motor with the addition of a commutator that can switch and control (alternate) current to the motor with built-in circutry.
The commutator can be solid state which operates with brushes, or it can be “electronically commutated” which makes use of semiconductors to operate the motor with efficiency gains.

How can we tell the difference between these types of motors?
Look for brushes. They wear and will need to be replaced.
IMG_20240116_212800
They should be accessable by removable caps. If you see these caps its a brushed motor.
IMG_20240116_212614

Look for the capacitor, that’s an AC induction motor. The green arrow points to the weird lump on the stator which contains tube capacitor.

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If you are unsure at any time of what type, exactly, your motor is, you can always rip the commutator, capacitor, or any other circuitry out of the motor to convert it to basic dynamo that will run at the speed provided by the frequency of the alternation of current directly to the coils of the motor.

And that is where I would like to resume the discussion, modifying a 12V car-battery inverter to switch it’s AC at a rate faster than 60hz. And thus drive the chainsaw faster. It would also be nice to include a soft start feature that increases the frequency in steps.

This 120V corded Bauer saw is nearly identical to mine.
IMG_20240116_213046

My goal in this thread is to run it in the field from a 12V car battery + inverter at higher speed by modifying the inverter’s AC frequency. Thanks, and Happy New Year!

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#13

Hi JoePA
A well layed-out, explanation post.
Looking back up my post was really off of your topic.
I can still delete it out.(DOW does have time lock-in feature that will eventually kick in.)
Or try to transfer it to a different topic thread if you wish. Errr. I tend to lose them doing this.
??? Up to you man.
Regards
Steve Unruh

#14

Harbor Freight conveniently posts user manuals for most of their products on their website. The current Bauer saw that looks like your photo appears to have a universal brush motor. You will probably need more voltage to run it faster. If you have a way to vary the voltage, you could try it. That would probably be easier than trying a different frequency. Something like a router speed control would not give you more speed, but would show you how the saw responds to changing voltage, though the speed control doesn’t exactly reduce the voltage (the effect is essentially the same). Harbor Freight has one for $18 that’s good for 8 amps. It might drive the saw with no load, if you raised the speed slowly to avoid a starting surge.

Warning: I haven’t tried this, so I don’t know for sure.

#15

Search up and read about Counter-EMF and back-EMF in motors.
This limits RPM. This is an in-motion dynamic factor.
Is design used to RPM set many motors working RPM maximums.
The maths are complex.

Like a bow wave effect in ships and boats.
S.U.

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#16

The biggest problem you are going to have is the motor most likely isn’t designed to go that fast. In theory it will work. In reality it will most likely overheat the windings and they will short out. If that doesn’t kill it, the bearings will blow out.

You might want to look at Variable Frequency drives, and I believe, you can get away with square waves.
This is probably a good place to get started although they don’t discuss universal motors.

#17

Classic winter arm chair fantasy. I will play a one paragraph round.
What do you want to do? Build a chainsaw or cut wood? Car batteries have a horrible cycle life while lithium ion batteries are similar in cost to AGM car batteries. Obviously money and time are not design constraints. The car battery will not move itself into the bush, so that is accomplished with either animal or fossil fuel power. I suspect by the time this project is implemented, there will solar power in abundance, to charge the car battery, which is the only practical aspect or reason for undertaking such a task.
The topic and summary sentences were left unwritten, but I think I managed to stay on focus. Namely, discussing operating an electric chainsaw on a car battery.
:slightly_smiling_face:

4 Likes
#18

The new BEV trucks that are coming out have both auxillary ports like 240v outlets and they will have “vehicle to home” or ‘vehicle to vehicle’ charging. But otherwise, I agree with your main point. :slight_smile:

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#19

What is ironic is that the Soviets did this very thing. They used 400 Hz electric chain saws with the power provided by a gas producer fueled generator. They used electric winches on high lines, or electric tracked tractors powered by birch sticks. Zniime17(?) I think it’s in the library here.
Their producers were positive displacement. Definitely for out door use!
I will look in the library.

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#20

I was at auction today standing in the snow for hours and I bought these 12V inverters for ten dollars.
One of them has a microcontroller/microprocessor (see orange arrow).
Both have yellow transformers to raise the voltage 10X from 12 to 120V.
The wires on the 12V side are thick and 120V are thinner.
Both have capacitors, lots of resistors, and there should be a transistor fed by an oscilator.

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I think the microcontroller-model which has the brown ciruct board will be easier to modify because the circuitry is larger.
Any help identifying components: Oscillator curuct, transformer, etc is much appriciated. Thanks again and have a nice day.

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#21

An oscillator typically looks like this and they are usually marked with the frequency.

I don’t see one. Any oscillation would occur before the transformer in the circuit because transformers need at least a pulsed current to work. If you want to measure voltage, you need to use AC on the multimeter, not DC after where it oscillates. And to understand what kind of waves it is producing, and oscilloscope is the easiest.

The microcontroller one might have a built in clock that regulates the frequency. it really depends on the design.

Here is kind of how to build one, but the driver they are using looks like it is only capable of 50hz or 60hz depending how a configuration pin is jumpered. (this is just the first one that popped up.) You are probably better off looking at variable frequency drive designs to be honest.

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