BionX throttle limiting issue

[3DBeerGoggles]

Hi, I have a bit of a... weird one here.

I have a BionX G2 motor system with 350W hub installed on the 20" front of a tricycle (don't ask me why, it's how I found it), so naturally it's a throttle based system. The battery pack was toast so I added two DC-DC converters (12V and 5V), terminated the Canbus lines to the battery with a resistor, and powered it off a LiFePo4 pack I already owned. This means the system powers on, motor runs on throttle, and so on - just no regen or battery level indicator.

So on to the problem - when I enter the console codes to see what the max speed and max throttle speed are (which isn't adjustable, oddly), they both show 32kph. However, the motor rolls off power when it it 22kph, even if you have the wheel spinning freely.

Any ideas?

Edit: Is it perhaps hitting an RPM limit? 32kph on a 26" rim is roughly 265ish RPM, which works out to... 23-24kph hmmm. If so, any way around it?

 

[amberwolf]

If it is hitting the RPM limit, then the only bypass (other than programming, if possible) I can imagine is if there is a separate speed sensor in the motor (or on the wheel) than just the position sensors used for operating the motor. If the controlller is in the motor (probably) then the sensor would probably be in there, too.

If there is, then you could put a "divider" between it and the controller, that halves the number of pulses the controller sees per wheel revolution.


If it uses the position hall sensors for speed data, this won't work.

 

[3DBeerGoggles]

Yeah, it's an integrated controller with hall effect sensors AFAIK. What's weird is that these motors are known to hit RPMs high enough to go 40-50kph on a 26" rim (with the limiter disabled), so I wouldn't expect any issues getting up to 32kph with a 20" rim based on the math there. Just seems weird they'd set the limit at 32kph on the controller but it still drops the drive off down at 23kph

I wish I could find an affordable solution to checking the programming on this, for all I know I could spend $200 on a canbus adapter only to find it makes no difference!

 

[amberwolf]

Does it have a place you can set the wheel diameter? If so, what is it set for?

IF it's set for 26" then what you see makes sense, but if it's set for 20", it's not.

If the system was built for a 26" wheel, but the motor was simply relaced into a 20" wheel, then that's probably why it's setup this way, and would just need to be set for the correct wheel size. (or have the speed restriction changed or removed).

If you look around in the various BionX threads, you might be able to find one of the people here that already has the adapters, software, etc., and could check / fix this. I know there are at least a couple of people that do.

 

[3DBeerGoggles]

Oh joy - I checked the tire circumference setting that's available on the console, and it was set for a 24" wheel, so it's actually going... 18kph, confirmed per my GPS

I set it to the correct diameter, and now the speedometer reads accurately but it goes no faster. I have to wonder if it's a combination of what you're describing - perhaps the menu I can access without the dongle only corrects the speedometer but doesn't affect the limiter's speed calculation. I suspect I'd need the dongle to tell the wheel it's a different size.

The hard part is trying to find someone I could try to borrow/rent/buy used the dongle from...

 

[guelao78]

Have you tried doing a calibration of the throttle? Search for ''bionx throttle calibration".
Would it be possible that you post some photos and information of the battery hack you did? Thank you.

Miguel

 

[3DBeerGoggles]

Yeah, I gave that a go too - no change. I have a BionX Bike Interface on the way, so I'll be poking around the internals to see if I can find a setting to blame there.

 

[3DBeerGoggles]

BBI Found the problem!

Console had rim and speed limits set properly, but the motor was set to 26" instead of 20" AND with a 25kph limit.

 

[amberwolf]

Glad it was "easy" (even if it required extra hardware to get to those settings).

 

[3DBeerGoggles]

Yeah, if nothing else it goes to confirm that replacing the OEM battery with my bodge job doesn't hurt it