Hi Andy, my bet is that the motor is going over speed due to lack of load and the controller is shutting it down. My second guess is the incorrect resistance in place of the thermistor. A thermistor has a resistance at a certain temp. Try placing a resistor in the circuit to appear as a good thermistor.
@@TheInfoworks its the only reason I can think of for the motor starting, then stopping. Some kind of safety feature, for over speed . Eg. Chain jumped off. Any thing to do with the thermistor, I'd imagine would be a no start. Not start then stop. When working with single to three phase vfds on high starting torque applications, "motor silp" is critical. I imagine that the chainsaw is similar. Going over speed due to no load will cause problems!
Hello Andy, as this is probably designed to run a Lithium battery at 36V, are you certain that this middle terminal isn't a balance wire between the two banks of 18v cells? I.e. it should see a 50% voltage on this terminal for the saw to correctly operate? I only ask this because you have to keep Lithium batteries within certain voltages and discharging any bank of cells below their set voltage causes damage to the cells within and it wouldnt surprise me that these have a wire in the middle to make sure they dont discharge bank too much. Since you've shorted the wire one way or another, or not connected it, it probably cuts out because it doesn't see 50% voltage. Your comment about this being an AC motor is correct, it'll probably be what is called "brushless" in today's sales tech talk. Brushless has the benefits of it being quieter.
I know nothing of Qualcast chainsaws, Andy, but I have met thermistors in smaller batteries - and also thermistors in general - they are not always a very low resistance when cold - you can get all sorts that start at a resistance and go up when hotter, or NTC types which start high and go low. So perhaps the controller in this saw is looking for that thermistor to be within a particular range of values before it's happy to drive the motor (properly). Just an idea. Maybe someone has this exact battery and could measure the cold resistance for you - good luck ! Cheers, Dave
Dave, thanks for your thoughts. I've tried several thermistors from various battery drills, they are all direct connection when cold. I assuming this is why a direct connection to negative gives some motor function and so this brings into doubt the motor controller, cheers
@@TheInfoworks Ok Andy - I have never measured the thermistor in a drill batt, so I have learned something ! (will measure my two when I am out in the workshop next) It's just possible that Qualcast haven't used exactly that type of thermistor though, if you had some other plain resistors to try in there rather than a dead short, you may get lucky. Actually a pot (variable resistor) of 1k or 2kohms would be a good test setup. I was going to ask how you have an unused saw but with no battery - I see it was an ex demo model - that's explained that ! Dave
@@noakeswalker Dave, yes it was a display unit, so it may be that it never worked, but the thermistors gave a direct connection with a continuity test, maybe about 1 ohm. Another comment suggests that the circuit sensors no load on the motor. This I think is worth investigating by putting the chain back on. Lets see what Lee does, Cheers
Just another thought Andy - there isn't a switch on the chain brake sending a false 'stop' signal back to the controller is there ? It's hard to see on the video. Just mentioning it in case you hadn't thought of it ! (if you do get it going, let us know the cause in another video if you'd like) Dave
Dave, yes it has an isolation switch to cut all power when the lever is forward, yep, checked that but thanks for the thought. I will keep in touch with Lee and bring an update, cheers
I have the same problem. The 3rd pin is marked "ID" on my lawn mower that uses the same battery that you need ( I don't have a battery either). My concern is that it is giving some digital ID signal to the tool to tell it it is the correct battery. Apparently Qualcast is the budget arm of Bosch, so maybe some answers lie there.
Further investigations by me. The motor is 2 wire, so you can bypass the clever electronics and just hard wire a battery to the switches. Also, I tried connecting the 3rd "ID" pin with a 10kOhm resistor, which is a common resistance for power tool battery thermistors, to ground and then to plus, no success. I also tried giving the pin zero, 18V and 36V, no success. I think it is doing some digital communication that I will find difficult to trick, so going to bypass the clever board.
@@elastoplastscavenger Hi, thanks for your info, it leaves a huge dis-satisfaction when companies lock out the customer. It starts with security screws and passes on to unobtainable pass words, and then this sort of pointless malarkey. Apple of course are one of the worst. You buy, and we let you use it for the moment. Cheers
@@TheInfoworks Hi Andy, I watched this yesterday and pondered it overnight. If the motor is indeed 3 phase then it must have some sort of a variable frequency drive between the battery and the motor. I played with 3 phase washer motors in a video a while ago. give them ac and they will dance, I think you did this too. add a cap and you can smooth out the dance. Presumably there is no harm in lashing two of the 3 wires to a variac and bringing it up to a low voltage gently, on ac. DC on a 3 phase ac motor acts as a brake. quite magic, so maybe this is a safety feature or a function to brake the motor/chain. If the VFD is pooched and it is getting a straight through DC voltage to the motor it may cause it to move a fraction of a rev (presumably to the nearest 1/3?) and then lock/brake. A simple test for this could be to spin it by hand before applying power and then add the power and see if the motor is braked. the downside is that if this is so then you need a new motor controller. I am getting 2.1kw on my partial solar system on these sunny days!
@@bootsowen Owen, yes lots to learn about battery powered tools and VFD inverters seem to be the way forward, many forklifts use the technology as the motors are more powerful and smaller. Great you are seeing some real solar generation benefits, that's enough to run a washing machine inc. the water heating, cheers
Hi Andy, my bet is that the motor is going over speed due to lack of load and the controller is shutting it down.
My second guess is the incorrect resistance in place of the thermistor. A thermistor has a resistance at a certain temp. Try placing a resistor in the circuit to appear as a good thermistor.
Tom, thanks for your thoughts, Lee will be reading these comments and working out what to do, no load, there's a thought, cheers
@@TheInfoworks its the only reason I can think of for the motor starting, then stopping. Some kind of safety feature, for over speed . Eg. Chain jumped off.
Any thing to do with the thermistor, I'd imagine would be a no start. Not start then stop.
When working with single to three phase vfds on high starting torque applications, "motor silp" is critical. I imagine that the chainsaw is similar. Going over speed due to no load will cause problems!
@@tomscum61 Thanks for the extra input, it's great and shows a real benefit of UA-cam, cheers
Hello Andy, as this is probably designed to run a Lithium battery at 36V, are you certain that this middle terminal isn't a balance wire between the two banks of 18v cells? I.e. it should see a 50% voltage on this terminal for the saw to correctly operate? I only ask this because you have to keep Lithium batteries within certain voltages and discharging any bank of cells below their set voltage causes damage to the cells within and it wouldnt surprise me that these have a wire in the middle to make sure they dont discharge bank too much. Since you've shorted the wire one way or another, or not connected it, it probably cuts out because it doesn't see 50% voltage.
Your comment about this being an AC motor is correct, it'll probably be what is called "brushless" in today's sales tech talk. Brushless has the benefits of it being quieter.
Philip, this comment has just popped up late. In this case we are certain it' a single battery pack, cheers
I know nothing of Qualcast chainsaws, Andy, but I have met thermistors in smaller batteries - and also thermistors in general - they are not always a very low resistance when cold - you can get all sorts that start at a resistance and go up when hotter, or NTC types which start high and go low. So perhaps the controller in this saw is looking for that thermistor to be within a particular range of values before it's happy to drive the motor (properly). Just an idea. Maybe someone has this exact battery and could measure the cold resistance for you - good luck ! Cheers, Dave
Dave, thanks for your thoughts. I've tried several thermistors from various battery drills, they are all direct connection when cold. I assuming this is why a direct connection to negative gives some motor function and so this brings into doubt the motor controller, cheers
@@TheInfoworks Ok Andy - I have never measured the thermistor in a drill batt, so I have learned something ! (will measure my two when I am out in the workshop next)
It's just possible that Qualcast haven't used exactly that type of thermistor though, if you had some other plain resistors to try in there rather than a dead short, you may get lucky. Actually a pot (variable resistor) of 1k or 2kohms would be a good test setup.
I was going to ask how you have an unused saw but with no battery - I see it was an ex demo model - that's explained that ! Dave
@@noakeswalker Dave, yes it was a display unit, so it may be that it never worked, but the thermistors gave a direct connection with a continuity test, maybe about 1 ohm. Another comment suggests that the circuit sensors no load on the motor. This I think is worth investigating by putting the chain back on. Lets see what Lee does, Cheers
Just another thought Andy - there isn't a switch on the chain brake sending a false 'stop' signal back to the controller is there ? It's hard to see on the video. Just mentioning it in case you hadn't thought of it !
(if you do get it going, let us know the cause in another video if you'd like) Dave
Dave, yes it has an isolation switch to cut all power when the lever is forward, yep, checked that but thanks for the thought. I will keep in touch with Lee and bring an update, cheers
I have the same problem.
The 3rd pin is marked "ID" on my lawn mower that uses the same battery that you need ( I don't have a battery either). My concern is that it is giving some digital ID signal to the tool to tell it it is the correct battery.
Apparently Qualcast is the budget arm of Bosch, so maybe some answers lie there.
Further investigations by me. The motor is 2 wire, so you can bypass the clever electronics and just hard wire a battery to the switches. Also, I tried connecting the 3rd "ID" pin with a 10kOhm resistor, which is a common resistance for power tool battery thermistors, to ground and then to plus, no success. I also tried giving the pin zero, 18V and 36V, no success. I think it is doing some digital communication that I will find difficult to trick, so going to bypass the clever board.
Also, all the markings on the printed circuit board yield no results on Google.
I should note that I am working on a tool from the same family but it is a hedge cutter with a 2 wire DC motor.
@@elastoplastscavenger Hi, thanks for your info, it leaves a huge dis-satisfaction when companies lock out the customer. It starts with security screws and passes on to unobtainable pass words, and then this sort of pointless malarkey. Apple of course are one of the worst. You buy, and we let you use it for the moment. Cheers
3 wire motor? Seen the same issue with some domestic DC fans, think about how a quadcopters work and I bet the ESC is gone mate!
You could test the windings too, but I doubt you own a 50v insulation tester.
Hi, thanks for the thoughts, as this is an ex display unit and never used it could quite have a faulty controller, cheers
@@TheInfoworks Hi Andy, I watched this yesterday and pondered it overnight. If the motor is indeed 3 phase then it must have some sort of a variable frequency drive between the battery and the motor. I played with 3 phase washer motors in a video a while ago. give them ac and they will dance, I think you did this too. add a cap and you can smooth out the dance. Presumably there is no harm in lashing two of the 3 wires to a variac and bringing it up to a low voltage gently, on ac.
DC on a 3 phase ac motor acts as a brake. quite magic, so maybe this is a safety feature or a function to brake the motor/chain.
If the VFD is pooched and it is getting a straight through DC voltage to the motor it may cause it to move a fraction of a rev (presumably to the nearest 1/3?) and then lock/brake.
A simple test for this could be to spin it by hand before applying power and then add the power and see if the motor is braked. the downside is that if this is so then you need a new motor controller.
I am getting 2.1kw on my partial solar system on these sunny days!
@@bootsowen Owen, yes lots to learn about battery powered tools and VFD inverters seem to be the way forward, many forklifts use the technology as the motors are more powerful and smaller. Great you are seeing some real solar generation benefits, that's enough to run a washing machine inc. the water heating, cheers