Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

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uula   100 µW

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Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by uula » Mar 08 2020 2:35pm

Greetings good folk of Endless Sphere,

I've bought an 80V Stiga chainsaw (same as Kobalt and Greenworks) to replace my 50cc gas saw. I'm hoping to run it from my 20ah 22s ebike batteries to get proper cutting time and avoid spending a fortune on the little batteries that normally come with it.

I've succesfully converted my Stihl MSA200 to run from a 36V 20ah backpack battery, but ended up having to swap the speed controller to a 120a HV Castle Creations RC ESC. I love the saw for woodwork and small pruning jobs but needed more power to run a decent size bar and a full chisel chain hence I'm curious to see how the 80V saw will perform.

I've tried to connect my battery directly to the speed controller of the 80V Stiga saw using the positive and negative terminals and I'm managing to get a little spin from the motor but it quickly cuts out and starts beeping and flashing red light. The fault appears also when I connect the battery and let it sit for a bit after switching it on. The saw uses a third terminal with a black wire going to the speed controller from what I believe is a tab labeled with 'C' on the battery (one next to the negative terminal). I suspect the speed controller is expecting some sort of a signal from there to operate correctly and was wondering if there are any Greenworks/Cobalt/Stiga 80V users on the forums who could help me out. I would be most grateful if someone that owns the batteries could make an attempt to measure the output from that terminal.

All the best,
Uula

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by torker » Mar 08 2020 3:01pm

I have on of those. It rips pretty good for me. On small stuff. 5 inch diam and smaller
I wonder if you could take the stock battery apart and see what the third wire is for.
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uula   100 µW

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by uula » Mar 09 2020 2:11am

I've watched a couple of teardown videos on those batteries on YouTube but they didn't to into sufficient detail. I bought the bare saw cheap without a battery so I'm just guessing just from what I saw on the internet.

markz   100 GW

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by markz » Mar 09 2020 1:05pm

An unknown 3rd terminal/wire could mean its for signalling, usually temperature is my guess. See where that 3rd unknown thing goes. I've watched a few tear down of power tools by channel "AvE" where he tears down and analyses the product in hand. Sometimes the temp signal will go to the casing of the motor, depending on how fancy the electronics are which can vary depending on price point and target consumer. "Durable" and "Pro" power tools you'd assume are spared no expense, how wrong is that. Save a penny, profit a fortune. Epoxy resined pcd boards are a nice touch and sometimes done. You need to find out the 3rd equation of your product in hand. The 3rd wire/terminal/connection whatever that may be.

uula   100 µW

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by uula » Mar 10 2020 9:27am

All looks pretty decent inside. Unfortunately the wire goes from the battery tray straight into the potted speed controller board.
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uula   100 µW

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by uula » Mar 10 2020 9:49am

Looks like I found a solution in a post by Warren: viewtopic.php?f=1&t=79384&start=75

Metallover from the forum posted a bit of code for arduino to fake a pulse through the com port to the speed controller to make it work. I'll give that a shot.

Other suggestions were to use just the com port from a working battery without draining it.

Many thanks!!

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by uula » Mar 10 2020 10:52am

Just an update, I programmed the arduino and checked with my pocket oscilloscope that there definitely is a pulse generated. Unfortunately the controller is not accepting the signal. I might go the route of buying the cheapest battery I can get and try to get the com signal from that.

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stan.distortion   100 W

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by stan.distortion » Mar 10 2020 11:06am

Sorry if it's a bit off topic but could you post a pic of the oil pump on that saw? I'm building a saw from the ground up at the mo and have a pump on order that will work but it's quite a big lump, with driver circuitry it will take up about the same space as the motor! Thanks.

EDIT: My best guess on the 3rd wire is temperature sensor, unless they're unusually high spec cells then they're pretty much pushed to their limit with the size of pack versus power needed.

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by spinningmagnets » Mar 10 2020 11:20am

I have often conducted experiments that ended up "bricking" the subject. That being said, it has sometimes worked.

I'd take the one battery pack that is the oldest/smallest/least likely to be useful, and cut open the case (some use a security torx bit, available on ebay).

Find the two end bushes, and attach a red/black pair of wires that you snake out a hole that you drill into the side of the case. Attach those two leads to the female connector of your choice (XT90?).

Charge both packs to the same exact voltage within 0.10V (greeworx plus your ebike pack), plug it in and see if that works. The stock pack will not understand why the Ah level is not going down while you are using it, but...it will not care.

Be aware, doing this might fry the tool battery, the tool controller, or your expensive ebike pack.

uula   100 µW

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by uula » Mar 10 2020 3:15pm

Hey Stan, here's a photo of the oil pump. Flimsy little thing that's run off a gear ring on the drive shaft. Very similar setup to the one on my Stihl MSA200. I've been thinking about building a saw from scratch, too! (But got lazy and went to attempt this project first) I've got a monster Turnigy CA120 outrunner waiting for that :) The Stihl uses a direct drive outrunner also and the chain brake is a spring steel band that clicks to tension around the outer casing. Pretty sweet! I was thinking about putting in a motorbike chain oiler to keep the oiler setup simple.
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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by uula » Mar 10 2020 3:23pm

Spinningmagnets, blowing stuff up sounds like my usual story, too :) I've had success converting my 36V DeWalt tools as you described so I'm feeling optimistic. Sounds like the guys on Warren's thread had success just pulling the com signal from the single terminal and leaving positive and negative disconnected and instead powering the speed controller directly from their own battery.

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stan.distortion   100 W

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by stan.distortion » Mar 10 2020 3:52pm

Thanks for the pic, I was hoping it was an electric pump but it looks like most (all?) electric saws are still using mechanical pumps :/ The one I'm planning to use is a ULKA NME, usually found in expresso machines but also used for oil in some applications, voltages might be an issue though. If you're interested I've converted a cheap saw as a testbed and will be doing a build thread shortly for one using pretty much the same electrics as e-skateboards, it should work out about on par with a 40-50cc saw.

markz   100 GW

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by markz » Mar 10 2020 11:34pm

The Magical Pixie Smoke
Breathe it ALL in!

uula wrote:
Mar 10 2020 3:23pm
Spinningmagnets, blowing stuff up sounds like my usual story, too :) I've had success converting my 36V DeWalt tools as you described so I'm feeling optimistic. Sounds like the guys on Warren's thread had success just pulling the com signal from the single terminal and leaving positive and negative disconnected and instead powering the speed controller directly from their own battery.

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by Punx0r » Mar 11 2020 8:27am

My guess was going to be a simple thermistor return in the "dumb" battery to the controller in the "smart" tool to provide battery temperature protection, but if it's a PWM signal serving some purpose or other that's a bit of a nuisance.

You might be able to salvage the board from a dead battery and strap it to your own battery, but there's a chance the board might permanently shutdown due to cell low-voltage detection.

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by uula » Mar 14 2020 9:49am

Thanks for the support folks. I've gone ahead an ordered a battery. I'll keep you posted If I discover another workaround to supply the com signal. All the best, Uula

uula   100 µW

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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by uula » Mar 20 2020 3:56pm

Got a 2ah battery and cracked it open to look for a thermistor but couldn't see one glued to a cell to my surprise. Tracing the com line on the bms seems to be a bit beyond me so I'll try and hook it up on the side of my big battery next. I've attached a couple of photos of the internals.
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Re: Need help with 80v Greenworks/Kobalt/Stiga chainsaw speed controller

Post by StinkyGoalieGuy » May 19 2020 1:01am

Hey uula, any update on this? I'm having the same issue. I bought a Greenworks brushless 60V blower. I built a battery for it and if I only connect to the + and - terminals on the tool, it powers up for about 3 seconds, then shuts off. If I wait a bit, it will power up for 3 seconds again, then shut off. I'm pretty confident it's not a low or saggy battery. It's built from A123 cells.

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