40v battery chainsaw skin only regulary $189, not my battery setup but might be useful for someone at $25!
Yard Force 40V Chainsaw (Skin Only) $25 C&C (Was $189) @ Mitre 10 Online
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pete1812 on 02/03/2022 - 15:08 mitre10.com.au (4314 clicks)
Last edited 02/03/2022 - 15:41 by 1 other user
Last edited 02/03/2022 - 15:41 by 1 other user
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@King Tightarse: So I did some more reading.
There's another 40v battery that is popular in the ebike scene. Apparently it requires a Digital signal to keep it alive. Else the behaviour is similar to what I'm seeing - runs for 2 seconds then shuts down.
I can only imagine this is done for security.
There is a workaround but it requires programming an Arduino to generate the signal which sounds like a lot of effort.
@edrift: how about just bypassing the board altogether and just get the chainsaw motor running, obviously doing this you won't have throttle control it, which isn't too bad lol. I'll spend time on this and get back for progress.
@lgacb08: Nah no can do. It's a brushless motor which means it requires the controller to trigger the 3 phase wires that power the motor.
@edrift: Hi Edrift.
Hows the test progressing.
I received mine today and was happy to see the bar will fit my stihl.
You probably already tried this but did you press in the button between the 4 pins.
I'm keen to repurposed the rest@wpw: No luck unfortunately.
That button in-between the pins isn't a button. It's just a spring loaded pin which helps eject the battery.
I pulled that part apart and it's not connected to anything electronic wise.Unless someone else can figure out the electrical side of things we are dead in the water.
I can easily whip up the battery mount design, but that seems pointless if I can't get it going
@edrift: The 18V AEG battery packs have a T1 and T2 terminal. I wonder if rigging up one of those might work for the comms part of it at least. The ozitos only have a single thermistor terminal I guess between that and gnd.
If someone gets hold of an actual pack, then those terminals could be probed to see what needs to be sent on them.
@stumo: Yeah the more expensive packs seem to pulse a digital 5v signal to the tool to identify itself. Would need an oscilloscope to view the signal. Getting all a bit too hard.
Such a shame because the hardware is all quite good, just restricted by stupid stuff like this.
Can understand why they charge so much for the batteries now. Half the cost is for proprietary security rather than the cells and BMS alone.@edrift: I did a bit of fiddling with them, with 4 pin from left to right, 1 is negative, 4 is positive, it appeared pin 3 voltage raised to 2.54v when the micro-controller detecting non original battery and stopped the motor. Pin 1 and 2 appeared to be ok to ground together but there's no continuity between them. I hooked up the arduino running some script found on eevblog but no success yet. Tried grounding pin 3 with 1 to create 0 voltage didn't help either. But this can be just guess work and we probably need an oscilloscope to dig further. I was thinking this BMS would act the same way as the other brands on eevblog (Greenworks).
Will try with more arduino stuff and get back here for progress. Pity passed a few free oscilloscope on gumtree in the last few months 😮💨@lgacb08: Ahh yes you found the same article I was reading.
I suspect it requires a similar but unique script to the greenworks one. Without an oscilloscope it would be guesswork.
Probably could go into a university or Tafe to test.. but would need the original battery to get a sample of the required signal.Even then I don't Arduino to play with, let alone dedicate one just to run the chainsaw.
@edrift: It could be as simple as a specific resistor to ground which opens the gate of a power transistor through pins 2,3.
One thing you could try is hooking up a variable resistor and slowly increasing the resistance. Again, 100% speculating and guessing but its possible.
The only way to really solve this puzzle is by testing a proper battery@King Tightarse: I already tried numerous resistor values:
1ohm
500ohm
1k ohm
10k ohm
20k ohm
30k ohm
100k ohm
0.5m ohmI originally thought that the resistor trick might do it if it was simply looking for a thermistor. But unless my tests were way off the expected resistance, then I don't think this is the case.
@edrift: That value spread should probably see some action, although it would be quite possible to have the gate open only within a narrow range, if that is their game. Equally, it could be looking for a specific voltage, although I would be cautious sending voltage upstream, seeing as we dont know where its going (might damage something on the control board)
I am not entirely sold on the idea of a digital key - it seems a bit over the top for something that doesn't have all that much brand identity to protect@King Tightarse: There much be decent protection because i was sending 40v into that 5v line and nothing seemed to break. It must clamp the voltage to logic line values.
Have been reading this:
https://www.eevblog.com/forum/reviews/greenworks-60v-battery…@edrift: Ha, fair enough. Any decent design will protect pins coming of the battery but with no-name branded stiff anything goes.
How do you know it wants 5v?
EDIT:
Read that forum post. The modus operandi does sound similar. Bastards if the went that far to "protect" it. Only way forward would be an original battery to test@King Tightarse: Not 5v specifically but most microcontrollers use 3-5v for signal. I was thinking it's more of 3v like the esp8266, not 5v. I have both but haven't tested on esp8266. But one that puzzles me was the 0v when the gate closes, opposite to what's written on those greenworks scripts. The board must have decent protection because I've tried shorting between pin 1, 2 and 3 and it still works.
@King Tightarse: When it throws the error (stops powering motor) I see 5v on one of those T lines (well it might be a signal of some sort, but I'm just using a multimeter not an oscilloscope).
The other work around is to buy a different brushless motor controller but then it's not getting very cost effective
Imagine waiting for a battery charge when a big tree trunk is cut more than 3/4 of the way… Won't take the risk of a battery powered chainsaw….
Batteries are removeable, so you just swap on another. Faster and safer than refuelling, and can be done in seconds without even taking the saw out of the cut.
Though petrol or battery, ideally you want to maintain situational awareness and ensure you have enough fuel / charge to finish your planned cut before starting it.
@King Tightarse, Hi are you any further with the project ? cheers
Hey Bertg, its edrift doing all the good work on this one - cheers
Thank you. Will ask him :-)
@edrift Hi are you any further with the project ? cheers.
Sorry mate I got stuck.
If I can't power the chainsaw it's pointless designing the 3d printed battery adaptor.
If someone can figure out how to easily power the chainsaw, then Im happy to CAD the physical battery mount.
Right now the chainsaw is a paperweight.
Thanks M8. I bought the saw & also the battery & charger. I have a heap of Ozito Batteries & was hoping to use them too haha. Cheers
If you're able to log the signal coming out of T1 and T2 pins of the genuine battery with an oscilloscope that would be a great help to getting us closer to solving this mystery.
Unfortunately I don't have the battery nor am oscilloscope to play with
@edrift: He has the battery - excellent! Also pls look for voltage and resistance on those pins. It could be something quite simple
@edrift
Hi, I now have the battery :-) I have no idea about anything Electronic please bear with me. I have feelers out for someone in my area who has an oscilloscope. If & when I find the person, exactly what do I ask them to do ? When you say log the signal is there a print out of the info ?
CheersNice one.
Probably a few things to check on the battery:
- Resistance (impedance) between T1 vs T2, T1 vs ground, T2 vs ground, T1 vs positive, T2 vs positive
- Using the oscilloscope, probe T1 vs T2 to see what signal (if any) is produced
If it's a PC/phone connected oscilloscope then you'll be able to get a screenshot.
Else you'll need to take a photo of the oscilloscope screen.Best case scenario is that #1 yields meaningful results.. This is because reproducing impedance is easy for the layperson to do (under guidance).
Worst case (and I suspect it to be this) is that #2 yields results and you see a Digital signal (pulses) coming off T1/T2.
This means one would have to be able to generate the same copy of that signal to feed into the chainsaw to use it.
That requires specific hardware and custom coding. More for the engineer than the layperson.
It would not really be cost effective to go down this route unless you already had an Arduino or similar microcontroller to work with.Thanks for the info. Will try to get it sorted asap.
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@edrift: If you can follow the traces, does it go to a semiconductor of some kind? If yes, you will be able to look up the inputs.
BTW kudos to you, you are really going for it!