Hello, i was wondering if i could wire a high amp toggle, on/off 2 pin switch onto 2 shunts in my 60a controller (3000w motor 52v 40ah battery), with one wire soldered onto each one, and than be able to switch on and off the shunt mod whenever i want. would this work?
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Shunt mod, but you can turn it on and off?
- Thread starter _Jo
- Start date
Daniel James
New here
long answer YES, short answer NO. lol.....
Care to elaborate?
docw009
Minor legend
The length of your wiring and switch will have too much resistance to work as a shunt,
There is a way to do it, but requires a little reverse engineering. Most controllers measure the current by sensing the voltage across a shunt resistor that is taking the entire battery current. One side goes to ground. The other side has a sensing line that goes to the microprocessor. Usually there is an op-amp between the sensing line and the uP. You can increase the current limit by placing a voltage divider on the sensing line (which is very low current). The divider can be switched or variable. Below is a diagram showing an adjustable 0 to 2x boost setup. You could place a switch across the top resistor to make it switchable. You need to cut the existing sensing line on the board to insert the divider. The sensing line is typically a very small trace.
One advantage is you don't need to change the main shunt resistor.
One advantage is you don't need to change the main shunt resistor.
Hmm i imagine that if we had fat enough cables/switch, it could function. If distance is very sensitive, maybe the switch could be located on the controller.
Daniel James
New here
i dont see why you couldnt put a switch on each shunt if you wanted to, my first controller had 3 shunts on the circuit board, it was good the way it was,,, put an extra one, that would probably trick the controller into thinking its sending less when iits sending more amps...
8AWG copper is about 0.6 mΩ per foot so if the switch is a foot way, that’s 1.2 mΩ. Typical shunt value for these controllers is around 1 mΩ. You could use the wire itself as the shunt mod by measuring out how much wire to parallel with the internal shunt(s); shorter wire, more power.
8awg is pretty thick!
I think maybe the switch itself would add a lot of resistance and you would need a huge one to overcome that.
What about using a mosfet? you can get them with a resistance ( when on ) in the 1 mΩ range. 5v exists in many obvious places on the controller to engage it.
With two 1 mΩ shunts in parallel, would we have an effective 0.5 mΩ?
I think maybe the switch itself would add a lot of resistance and you would need a huge one to overcome that.
What about using a mosfet? you can get them with a resistance ( when on ) in the 1 mΩ range. 5v exists in many obvious places on the controller to engage it.
With two 1 mΩ shunts in parallel, would we have an effective 0.5 mΩ?
The resistance of the switch and wires will be in the same ballpark as the shunt. The switch resistance will tend to vary depending on how the contacts touch and not be consistent. Copper wire also has a bigger temperature coefficient than a typical shunt resistor, so your current limit will drop a little as it heats up.
The FET idea is interesting, but not sure how that would behave in real life. It might need a heat sink. You could probably estimate things by looking at the datasheet.
The FET idea is interesting, but not sure how that would behave in real life. It might need a heat sink. You could probably estimate things by looking at the datasheet.
lnanek
Power poster
Isn't the shunt mod just a method to trick a non-programmable controller into outputting more amps? Seems like it would be pretty easy to just do the mod, then modify your throttle to have a switch to not use the full voltage range for your low speed mode instead of using a different shunt for low speed mode. There's plenty of threads about modifying throttle ranges using resistors and potentiometers.
Maybe your question is part of the answer. The OP didn’t explain why he wants to have this ability. I assumed to control current/power. If the cheap controller were speed based, then the throttle mod would limit speed, but if it used current control, then it could limit current/power. But, if he has a controller with a display, programmable or otherwise, the power readings of the display would be inaccurate with the shunt mod. With the switchable shunt mod, he could run normal, with accurate display readings, but flip to full power “who cares what the power is” mode when he needs it. Anyway, just a possible reason, the actual context may make more sense.
Great discussion so far. Fechter is right about some flaws with the switch, even if you pull it off.
In my case, i usually have a very hot tune but occasionally want to turn it down and pedal more, but neither a throttle nor PAS provide a good option to say, cut the power in half while i pedal furiously.
It's becoming more common for controllers to be torque based.
I've read a lot of things about hall sensor mods but never seen anyone actually do one.
Since the ol' '3 speed switch' seems to have gone extinct in controllers, it would be good to have a known good configuration that works on a majority of common 3 wire throttles
In my case, i usually have a very hot tune but occasionally want to turn it down and pedal more, but neither a throttle nor PAS provide a good option to say, cut the power in half while i pedal furiously.
It's becoming more common for controllers to be torque based.
I've read a lot of things about hall sensor mods but never seen anyone actually do one.
Since the ol' '3 speed switch' seems to have gone extinct in controllers, it would be good to have a known good configuration that works on a majority of common 3 wire throttles
The cheap dumb controllers still have them. I’d like to find one that has a pushbutton speed control as well. Everything now seems to use the more dangerous type that automatically engages when keep a constant speed. I probably won’t get any controllers without the 3 speed since it’s simple and does what I want without a bunch of button clicking.
Yes, i want a mode where i can just go ham when i want, and turn it off when i dont want to ruin my controller
Cause I need the extra torque a shunt mod gives me.
I get what he's talking about.
I also want a power level that changes from bike power to moped power, dependent on a switch.
I know of zero good quality programmable controllers that have this feature. Please correct me if i'm wrong.
I also want a power level that changes from bike power to moped power, dependent on a switch.
I know of zero good quality programmable controllers that have this feature. Please correct me if i'm wrong.
TPEHAK
Regular
INNOTRACE Shrimp does it. You just select the support level with the buttons on the Bafang display and it limits the maximum power depending on the support level you selected with the display.
TPEHAK
Regular
You can buy it on JLCPCB. If you want to save money you can buy bare PCB with stencils on JLCPCB and solder it home.
Here are the motor controller purchase instructions
Here are the motor controller purchase instructions
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lnanek
Power poster
Shouldn't Grin's [CycleAnalyst or maybe even just headless Super Harness] + MF switch accessory control + [Phaserunner or Baserunner controllers] be able to do this? Maybe even with any generic controller if you use Grin's external shunt.
My CycleAnalyst is often in diagnostic mode with the little lower case letters, like "awst" or whatever, and whatever is limiting things capitalized. So I assume it could be setup to limit amps and capitalize A. I think I've seen it has selectable modes as well, although typically used for when you plug a different battery in. So it should be possible to setup two different battery modes with different max amps and select between them with the switch.
I've actually programmed my Baserunner from my Android phone on the handlebars before too to change max battery amps when plugging in a battery blender or whatever as well. That's not one touch, though.
_Jo, what exact controller do you have?
I still see some cheap controllers with the 3 speed switch.
One of my bikes has one that you can program each of the 3 speeds for different current limits (and speed limits). I have all the speed limits disabled and just have 3 current limits. This works well in practice. The lower limit will keep the motor from overheating longer (and be in the legal range).
I still see some cheap controllers with the 3 speed switch.
One of my bikes has one that you can program each of the 3 speeds for different current limits (and speed limits). I have all the speed limits disabled and just have 3 current limits. This works well in practice. The lower limit will keep the motor from overheating longer (and be in the legal range).
Just leave the shunt mod in place and take control of your throttle hand to not cook your controller. Say you switch the shunt mod on. At some point your brain kicks in to shut it off before you cook the controller. Use that same brain signal and direct it to your throttle hand, and ease up on it.
