How to solder the onimous shunt on the KU63
- Thread starter schwibsi
- Start date
rocwandrer
100 W
When it arrives, I plan to do the opposite mod and cut back some material from the shunt on a KU123 (and/or maybe the KU63) to get a lower amp limit, to protect my low amp-hour batteries. Any unintended consequences to be concerned about here?
friendly1uk
1 MW
gsl said:The question remains, why can't I get Rtune to work as intended? But if you could help, you would have done so...
I have read here that this topic was discussed on many occasions but I don't seen to be able to find those discussions in the search. Could you maybe point me to relevant threads so I can better understand the mod or find alternatives?
Thanks
I can't find anything on the subject either. Just this link offered here, that shows where R1 goes, and gives some value's. Then it goes on to say if that won't work, you need R2 aswell. But no comments on the spec or pictures of it's location. It's there on the schematic diagram though.
This thread has a second unrelated question about cutting the board during a different mod. It seems to of added some confusion. That or I should give up now.
Perhaps someone knows by now. Time is passing by...
friendly1uk
1 MW
Picking this and that from various post's, I have come up with this
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My understanding is the shrunk part of the diagram switch's 3 phases, and they all ground through that one shunt. The common rail above the shunt is where the samples are normally taken from. In an idle state this common rail is not far off zero volts, as its tied to it through that large shunt resistor. As currant starts to flow, voltage starts to increase on this common rail. Never amounting to much because it's grounded through that shunt, but still enough to measure. The higher the voltage, the more currant in the ecu's eyes. At some point it will see enough voltage on this common rail to start currant limitation.
What I have done is make a new common rail to feed the two small sensor circuits. It offers a proportion of the original common rails voltage. The proportioning being done with a variable resistor. We could use perhaps a 10 ohm variable. With the arm at the top, you would see full rail voltage. With it turned to the middle you would see only half the rail voltage. If of course you can see through the smoke. Yes.. with further thought I have missed a component. A fixed resistor in series with the variable on the ground side. To keep me further away from ground.
Must resist mixing beer with internet. It's looking right enough for now though
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My understanding is the shrunk part of the diagram switch's 3 phases, and they all ground through that one shunt. The common rail above the shunt is where the samples are normally taken from. In an idle state this common rail is not far off zero volts, as its tied to it through that large shunt resistor. As currant starts to flow, voltage starts to increase on this common rail. Never amounting to much because it's grounded through that shunt, but still enough to measure. The higher the voltage, the more currant in the ecu's eyes. At some point it will see enough voltage on this common rail to start currant limitation.
What I have done is make a new common rail to feed the two small sensor circuits. It offers a proportion of the original common rails voltage. The proportioning being done with a variable resistor. We could use perhaps a 10 ohm variable. With the arm at the top, you would see full rail voltage. With it turned to the middle you would see only half the rail voltage. If of course you can see through the smoke. Yes.. with further thought I have missed a component. A fixed resistor in series with the variable on the ground side. To keep me further away from ground.
Must resist mixing beer with internet. It's looking right enough for now though
friendly1uk
1 MW
Much time later..
I can see the light. The OP was linking to physically large resistors at 5 Watts. Such a size could go straight across the shunt. A 15mOhm resistor across the 5mOhm shunt, would by my reckoning, raise the 15 limit too 20. It would be about 4W being dissipated.
I'm still scratching my head over an R2 value, but firstly why it needs one. I have just about crunched every number I can think of, including the expected voltages at the cpu under a few conditions. It's an almost linear change to both when you solder. I will go through it again when I can hold my head up.
Anyone got a link I should see? I'm at a loss over this one.
I can see the light. The OP was linking to physically large resistors at 5 Watts. Such a size could go straight across the shunt. A 15mOhm resistor across the 5mOhm shunt, would by my reckoning, raise the 15 limit too 20. It would be about 4W being dissipated.
I'm still scratching my head over an R2 value, but firstly why it needs one. I have just about crunched every number I can think of, including the expected voltages at the cpu under a few conditions. It's an almost linear change to both when you solder. I will go through it again when I can hold my head up.
Anyone got a link I should see? I'm at a loss over this one.
friendly1uk
1 MW
I'm on it now. Finally pieced it all together. It was all out there (mostly from Jeremy) I just couldn't find it.
I will write it out here too.
The chip watch's the shunt with two separate circuits for two separate reasons. Pin 9 watch's and it is concerned with running currant. Pin 19 also watch's and it is concerned with over currant protection. If you mod the shunt to lower it's resistance, you effect both running currant and the over currant protection threshold. The R1 mod just effects the running currant. It is said that 3.3K would double the currant. I guess at some point, with some motors, your going to increase the possible surge currants so much that the safety circuit is unhappy with it. Meaning that also needs modding. That is the R2 mod. I would not be surprised if this R2 mod was purely academic principle though.
Just having a stab at it, I would say a 100K R2 value would give maybe a 10% increase in over currant threshold. My reasoning is that your making a voltage divider with R78. However, 10k and 100k are big. You might want to drop them both down 50%. I could do with this verifying, but I believe R78 is just currant limiting and the pin 19 is used to seeing full shunt voltage. So a divider is an easy solution.
I will write it out here too.
The chip watch's the shunt with two separate circuits for two separate reasons. Pin 9 watch's and it is concerned with running currant. Pin 19 also watch's and it is concerned with over currant protection. If you mod the shunt to lower it's resistance, you effect both running currant and the over currant protection threshold. The R1 mod just effects the running currant. It is said that 3.3K would double the currant. I guess at some point, with some motors, your going to increase the possible surge currants so much that the safety circuit is unhappy with it. Meaning that also needs modding. That is the R2 mod. I would not be surprised if this R2 mod was purely academic principle though.
Just having a stab at it, I would say a 100K R2 value would give maybe a 10% increase in over currant threshold. My reasoning is that your making a voltage divider with R78. However, 10k and 100k are big. You might want to drop them both down 50%. I could do with this verifying, but I believe R78 is just currant limiting and the pin 19 is used to seeing full shunt voltage. So a divider is an easy solution.
Great work in figuring it out, but, as you say, it's all academic when it comes to achieving higher currents.
I've soldered shunts on many low current controllers, taking them from 15 amps to as high as 24 amps, and I've never had a problem. Soldering the shunt takes seconds. I connect my watt-meter, solder a bit, power up the motor and apply the brake to slow it right down to measure the max current, then repeat until you get the value you want. The controllers are cheap anyway, so if it all goes tits up.you can buy a new one, though I've never had to. Cutting tracks and soldering resistors onto SM connections is not easy for the average amateur. Also, loads of people have done it on the UK Pedelecs forum, and I've never heard any of them ever report a failed controller.
What happens if you allow 24 amps continuous current, but don't increase the allowed surge current? What's the surge current set to? You could end up solving one theoretical problem, but create another.I know which method I'll continue to use in the future.
I've soldered shunts on many low current controllers, taking them from 15 amps to as high as 24 amps, and I've never had a problem. Soldering the shunt takes seconds. I connect my watt-meter, solder a bit, power up the motor and apply the brake to slow it right down to measure the max current, then repeat until you get the value you want. The controllers are cheap anyway, so if it all goes tits up.you can buy a new one, though I've never had to. Cutting tracks and soldering resistors onto SM connections is not easy for the average amateur. Also, loads of people have done it on the UK Pedelecs forum, and I've never heard any of them ever report a failed controller.
What happens if you allow 24 amps continuous current, but don't increase the allowed surge current? What's the surge current set to? You could end up solving one theoretical problem, but create another.I know which method I'll continue to use in the future.
Could you maybe post a picture, where these resistors are on a KU123?
I have an issue with my new controller. I added some solder, but it shuts down, when I open up the throttle to more than a quarter, when I'm on the bike.
When the rear wheel is lifted up, it will spin full-speed. However, when I start applying the brakes, it'll go up to close to 30A, and then make a noise shut down.
I plan to install 3077 fets and ultralow ESR capacitors, so the heat from 50-60A peak should be fine, but I think I need to change the resistor values to allow for the higher current.
I'll use a speedict mercury to adjust the current limits later. So anything up to 70A peak would be fine.
I have an issue with my new controller. I added some solder, but it shuts down, when I open up the throttle to more than a quarter, when I'm on the bike.
When the rear wheel is lifted up, it will spin full-speed. However, when I start applying the brakes, it'll go up to close to 30A, and then make a noise shut down.
I plan to install 3077 fets and ultralow ESR capacitors, so the heat from 50-60A peak should be fine, but I think I need to change the resistor values to allow for the higher current.
I'll use a speedict mercury to adjust the current limits later. So anything up to 70A peak would be fine.
Are you sure it's the controller shutting down and not the battery? The BMS also normally has current limiting unless you're using lipos. You can also get voltage sag in the battery at high current, which will also cause the BMS to cut off. You can pput a voltmeter on the wires between the battery and controller to confirm which is cutting off when you do your brake test.schwibsi said:
Current limiting by the controller is seamless. You don't know it's happening, and it doesn't shut-down anything.
It'll shut-down if it goes over temperature, but that takes quite a long time. The only other reasons I can think of are interrupted supply voltage, or ignition wire.
I've also had shutting down with a faulty hall connector, where the controller detected the fault, so was trying to switch to sensorless mode, but it needs the throttle to be re-initialised before it'll give power.
The noise bit is also worrying me, which, if coming from the motor, indicates a phase or hall problem.
A standard KU123 will give 30 to 32 amps without a soldered shunt.
It'll shut-down if it goes over temperature, but that takes quite a long time. The only other reasons I can think of are interrupted supply voltage, or ignition wire.
I've also had shutting down with a faulty hall connector, where the controller detected the fault, so was trying to switch to sensorless mode, but it needs the throttle to be re-initialised before it'll give power.
The noise bit is also worrying me, which, if coming from the motor, indicates a phase or hall problem.
A standard KU123 will give 30 to 32 amps without a soldered shunt.
friendly1uk
1 MW
I think the ku123 uses the same chip as the ku63. Both are pictured here: http://www.avdweb.nl/solar-bike/electronics/ku63-motor-controller.html#h0-1-19-ku123anbspmotor-controller
If they are the same chip, then that is where the resistors go.
I think something went wrong when you soldered your shunt. I suspect a timing issue the controller can work through when free wheeling.
IIRC the 123 can cycle through a set-up procedure which includes swapping halls around. You decide when it gets it right. If this is so, then It might of done things you don't know about. It's the 93 or 123, I forget which and also how.
If they are the same chip, then that is where the resistors go.
I think something went wrong when you soldered your shunt. I suspect a timing issue the controller can work through when free wheeling.
IIRC the 123 can cycle through a set-up procedure which includes swapping halls around. You decide when it gets it right. If this is so, then It might of done things you don't know about. It's the 93 or 123, I forget which and also how.
ezzpete
1 mW
I have a CON61 controller from GBK. This morning I opened it for the first time, and was surprised to see the shunt had already been soldered. Either the factory or GBK must have done it??
I've had a few controllers that have already been soldered too. It might be because they supply the same controller to someone else at a lower current - like 12 amps that used to be more common, so they solder it to get a 15 amp version. A lot of these controllers are assembled in small workshops, not massive factories.
