Repairing a shunt on a mainboard

General Discussion about electric bicycles.
ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Repairing a shunt on a mainboard

Post by ebike11 » Apr 18 2020 1:21pm

HI guys
I have a 50A controller and unfortunately I have to lower the amps rather than increasing the amps that most people do via shunt mod. There are 3 shunt bars side by side. I snipped off a small part of one on the shunt but I still needed to lower the amps because the battery pack that I have only has cells with a continuous discharge of 30A. Its a small build for another bike. I tried snipping a bit more off from the shunt bars but I accidently severed the remaining 2 bars and there is a gap in the center. What could I use along with solder to make the connection again? The original shunt bars are pretty stiff.
Thx

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 19 2020 12:19am

Anyone have to do this before?

docw009   100 kW

100 kW
Posts: 1328
Joined: Aug 02 2015 7:43am
Location: Chicago area suburbs.

Re: Repairing a shunt on a mainboard

Post by docw009 » Apr 19 2020 11:38am

Why not copper wire?

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 19 2020 12:58pm

docw009 wrote:
Apr 19 2020 11:38am
Why not copper wire?
Yes i will try tomorrow and solder
So the controllet stopped working after all 3 shunts were cut. Is that a normal thing for it to do?

User avatar
DogDipstick   10 kW

10 kW
Posts: 717
Joined: Aug 19 2018 12:39pm
Location: Fleetwood Pa

Re: Repairing a shunt on a mainboard

Post by DogDipstick » Apr 19 2020 2:13pm

viewtopic.php?t=31643

Best shunt mod thread I have found yet. Explains alot on how they work typically.

... and by cutting all three... you would increase resistance and reduce current (to zero apparently lol).
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Waddyamean? You cant tell me how many amperes/Ft.^2 of the plate ?!?!? WTF. :x :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

markz   100 GW

100 GW
Posts: 10873
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: Repairing a shunt on a mainboard

Post by markz » Apr 19 2020 3:03pm

Shunt are sense wires, the less shunt material the less current while the more shunt material (soldering equal amounts to each shunt) the more current. I would have just cut one shunt out of the 3 to reduce to 2/3 of total. So if your controller was 45A, it would now be 30A, is my best guess. They would be in parallel, so 10//10=5 and 10//10//10 is 5//10 is 3.33 total so cutting one out is 10/10=5 so more resistance. Parallel resistance equation^^^^^^^^^^^^^^^^^^^^

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 29 2020 12:30am

DogDipstick wrote:
Apr 19 2020 2:13pm
viewtopic.php?t=31643

Best shunt mod thread I have found yet. Explains alot on how they work typically.

... and by cutting all three... you would increase resistance and reduce current (to zero apparently lol).
Yes when I cut one and tested, the bike ran fine. Then I cut the other 2 shunts in half causing a gap and the bike never moved when the throttle was twisted. I soldered the shunts together, but still nothing. Would something have caused no power signal to the motor? maybe cutting all 3 shunts allowed something else to malfunction?
I see no burnt marks on the board

bww129   100 mW

100 mW
Posts: 35
Joined: Apr 14 2020 7:44am
Location: Lancaster PA, USA

Re: Repairing a shunt on a mainboard

Post by bww129 » Apr 29 2020 5:23am

Obviously you don't know what value the shunts were, but have you searched to see if someone else has reported their value? What controller is it? Can you post a picture of what they look like?

If the controller is trying to read the phase current but you effectively changed the resistance to infinity then the voltage across it will be high and could activate the hardware protection, assuming it has that.

I would have expected that bridging each shunt with solder would have temporarily restored operation as long as nothing else was damaged.

User avatar
MadRhino   100 GW

100 GW
Posts: 7009
Joined: Sep 03 2010 5:28pm
Location: Montreal QC Canada

Re: Repairing a shunt on a mainboard

Post by MadRhino » Apr 29 2020 6:37am

The 5v circuit may be defective now, first thing to test.

Cutting all the shunts was not the best idea of the month. :wink:
To restore (at least one), I would have soldered on it a jumper of copper wire about the same gauge.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 29 2020 7:56am

bww129 wrote:
Apr 29 2020 5:23am
Obviously you don't know what value the shunts were, but have you searched to see if someone else has reported their value? What controller is it? Can you post a picture of what they look like?

If the controller is trying to read the phase current but you effectively changed the resistance to infinity then the voltage across it will be high and could activate the hardware protection, assuming it has that.

I would have expected that bridging each shunt with solder would have temporarily restored operation as long as nothing else was damaged.
its a 72V greentime controller 45A model, but I cant find it in his store now
Yes I bridged with solder but Im assuming something else must have got damaged :(

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 29 2020 7:59am

MadRhino wrote:
Apr 29 2020 6:37am
The 5v circuit may be defective now, first thing to test.

Cutting all the shunts was not the best idea of the month. :wink:
To restore (at least one), I would have soldered on it a jumper of copper wire about the same gauge.
Yeah, not the best idea for sure. I did solder after the damage was done but nothing.
Where is the 5V circuit usually located?
i can upload of the opened controller if needed thx

User avatar
dogman dan   100 GW

100 GW
Posts: 35732
Joined: May 17 2008 12:53pm
Location: Las Cruces New Mexico USA

Re: Repairing a shunt on a mainboard

Post by dogman dan » Apr 29 2020 8:23am

Time to just buy a new one, to use while you work on this one. Unless you have a spare already.

User avatar
MadRhino   100 GW

100 GW
Posts: 7009
Joined: Sep 03 2010 5:28pm
Location: Montreal QC Canada

Re: Repairing a shunt on a mainboard

Post by MadRhino » Apr 29 2020 8:43am

Yep, good to have spares, for a commuter especially.

Test the 5v circuit on throttle, or phase red/black
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

User avatar
amberwolf   100 GW

100 GW
Posts: 30787
Joined: Aug 17 2009 6:43am
Location: Phoenix, AZ, USA, Earth, Sol, Local Bubble, Orion Arm, Milky Way, Local Group
Contact:

Re: Repairing a shunt on a mainboard

Post by amberwolf » Apr 29 2020 4:38pm

FWIW, the shunts *are* the battery-negative connection for the controller.

Without the shunts, there's no power.

Wiring across the shunts restores power but leaves the controller unable to know how much current is flowing, and thus unable to protect itself against overcurrent, and vulnerable to failure upon any usage.

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 29 2020 9:37pm

dogman dan wrote:
Apr 29 2020 8:23am
Time to just buy a new one, to use while you work on this one. Unless you have a spare already.
ok ill try it

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 29 2020 9:37pm

amberwolf wrote:
Apr 29 2020 4:38pm
FWIW, the shunts *are* the battery-negative connection for the controller.

Without the shunts, there's no power.

Wiring across the shunts restores power but leaves the controller unable to know how much current is flowing, and thus unable to protect itself against overcurrent, and vulnerable to failure upon any usage.
thx for the info!

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 30 2020 2:27am

MadRhino wrote:
Apr 29 2020 8:43am


Test the 5v circuit on throttle, or phase red/black
phase red/black? the phases wire are green, blue and yellow

User avatar
MadRhino   100 GW

100 GW
Posts: 7009
Joined: Sep 03 2010 5:28pm
Location: Montreal QC Canada

Re: Repairing a shunt on a mainboard

Post by MadRhino » Apr 30 2020 3:11am

ebike11 wrote:
Apr 30 2020 2:27am
MadRhino wrote:
Apr 29 2020 8:43am


Test the 5v circuit on throttle, or phase red/black
phase red/black? the phases wire are green, blue and yellow
Sorry. Brain fart. I meant halls red/black.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

markz   100 GW

100 GW
Posts: 10873
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: Repairing a shunt on a mainboard

Post by markz » Apr 30 2020 5:05am

Unless there is something "great" about your controller, some feature that stands above the rest then just buy a new controller to suit your voltage and discharge amp requirements. Then you can go to www.mouser.com and by some shunts, guessing as to what ohmic (resistive/resistor value) it was stock. It will be a low ohmic value, like 0.10 or a 0.05 ohm or something along that lines, very low.

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 30 2020 5:18am

MadRhino wrote:
Apr 30 2020 3:11am
ebike11 wrote:
Apr 30 2020 2:27am
MadRhino wrote:
Apr 29 2020 8:43am


Test the 5v circuit on throttle, or phase red/black
phase red/black? the phases wire are green, blue and yellow
Sorry. Brain fart. I meant halls red/black.
tested and I have 5v in both places. its weird why there is no signal..tested motor halls and coils. they are also both good
Its gotta be in the controller

User avatar
MadRhino   100 GW

100 GW
Posts: 7009
Joined: Sep 03 2010 5:28pm
Location: Montreal QC Canada

Re: Repairing a shunt on a mainboard

Post by MadRhino » Apr 30 2020 7:46am

Maybe you did mod the shunt resistance enough so, that the Amp signal is now reading a value that is out of the controller program setting.

I agree that you should have a spare controller to ride the bike while you are playing with this one.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 30 2020 8:21am

MadRhino wrote:
Apr 30 2020 7:46am
Maybe you did mod the shunt resistance enough so, that the Amp signal is now reading a value that is out of the controller program setting.

I agree that you should have a spare controller to ride the bike while you are playing with this one.
hi
in other words, i put too much solder over the shunts?
also this controller has no programming capabilities or bluetooth

User avatar
fechter   100 GW

100 GW
Posts: 14985
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

Re: Repairing a shunt on a mainboard

Post by fechter » Apr 30 2020 10:29am

Most controllers I've seen use something like a LM358 to measure the voltage across the shunt. Normally the input would be millivolts, but if the shunt resistors were all open circuit, the LM358 (or whatever is looking at the shunt voltage) could see full pack voltage and self-destruct.
"One test is worth a thousand opinions"

User avatar
MadRhino   100 GW

100 GW
Posts: 7009
Joined: Sep 03 2010 5:28pm
Location: Montreal QC Canada

Re: Repairing a shunt on a mainboard

Post by MadRhino » Apr 30 2020 10:58am

ebike11 wrote:
Apr 30 2020 8:21am
MadRhino wrote:
Apr 30 2020 7:46am
Maybe you did mod the shunt resistance enough so, that the Amp signal is now reading a value that is out of the controller program setting.

I agree that you should have a spare controller to ride the bike while you are playing with this one.
hi
in other words, i put too much solder over the shunts?
also this controller has no programming capabilities or bluetooth
No, If you had lowered resistance of the shunt, the controller would be working, only not ‘knowing’ it is feeding higher power. But, if you raised the resistance of the shunt too high, the controller program could shut the power off, thinking the max Amp setting is attained or busted.

This can happen if you had replaced the copper shunt material with solder that has a higher resistance (lead has only 7% of copper conductivity, thin is about 15%). Normally we do the opposite. I mean we are ADDING solder to the copper shunt, to lower the shunt resistance slightly, or add an extra shunt to lower resistance considerably. This is tricking the controller thinking it is feeding power within its limit setting, when it is really feeding much more. Now, bridging with solder, you may have tricked it thinking it had reached the limit, even at rest.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

ebike11   100 kW

100 kW
Posts: 1469
Joined: Nov 16 2013 8:01pm
Location: far away

Re: Repairing a shunt on a mainboard

Post by ebike11 » Apr 30 2020 12:04pm

MadRhino wrote:
Apr 30 2020 10:58am
ebike11 wrote:
Apr 30 2020 8:21am
MadRhino wrote:
Apr 30 2020 7:46am
Maybe you did mod the shunt resistance enough so, that the Amp signal is now reading a value that is out of the controller program setting.

I agree that you should have a spare controller to ride the bike while you are playing with this one.
hi
in other words, i put too much solder over the shunts?
also this controller has no programming capabilities or bluetooth
No, If you had lowered resistance of the shunt, the controller would be working, only not ‘knowing’ it is feeding higher power. But, if you raised the resistance of the shunt too high, the controller program could shut the power off, thinking the max Amp setting is attained or busted.

This can happen if you had replaced the copper shunt material with solder that has a higher resistance (lead has only 7% of copper conductivity, thin is about 15%). Normally we do the opposite. I mean we are ADDING solder to the copper shunt, to lower the shunt resistance slightly, or add an extra shunt to lower resistance considerably. This is tricking the controller thinking it is feeding power within its limit setting, when it is really feeding much more. Now, bridging with solder, you may have tricked it thinking it had reached the limit, even at rest.
Thanks for that info MadRhino..hmm so I guess maybe I should remove all of the large glob of solder and start over. Maybe bridging the shunt gap with thin copper wire instead of bridging the gap with solder??

Post Reply