Another Bionx question

[Good Twin]

Hello, somewhat long time lurker here, could use some advice. I searched the forums but couldn't find a clear answer for my question that is this.
I have a pair of older Trek 7200’s with 350W direct drive motors, 40V, 11S4P battery packs which are mostly dead. The batteries in the pack are Sony’s with no BMS that I could find.

On one of the packs I removed the battery and brought the leads out externally and connected a 36V, 8 amp battery and for the most part is works except when going up a hill the motor quits which i suspect is due to a low voltage cutoff. I think that this is the older I2C bus system if that makes a difference.
So the question is can i hook up a 48V battery pack and not let the magic blue smoke out? Will these old bionx motors work when overdriven voltage wise?
Thanks

 

[lnanek]

Every bionx hub (which all have integrated controllers inside them as well) I've ever tried has taken 48v upgrades fine.

AFAIK they only made one controller mostly and just didn't populate some of the MOSFETs on the weaker ones. So the controllers differ in the amount of current they can take before overheating, but not the voltage. I've heard later controllers even upgraded the FETs to 100v capable instead of 60V, but not the caps, unfortunately.

I've only tried CANBus capable ones, though. Never old enough to be I2C. I've never fed that extra voltage into the batteries either. There is a special firmware you can flash that lets you set Vmax higher too.

 

[Good Twin]

Thanks, that is what I was looking for, appreciate the help.

 

[Cephalotus]

This is a CAN bus system. There is a BionX BMS (usually Typ 5.2) inside those battery packs, it just lacks balancing cables or single cell voltage monitoring. ( actually i once have seen an 11s BionX batery using the 13s 48V BMS with modification)

I strongly advice against connecting these 11s / 40V BMS with a 13s battery.

I asume Inanek is taking about replacing 36V/40V Bionx batteries with 48V Bionx batteries which have their own 48V BMS. This works fine with most BionX system, but can kill the very old 26V or 22V drives, but those have become rare these days.

But you just want to connect the new battery to the old BMS.

Use a 11s battery! (add your own BMS with single cell monitoring)

Your old packs with LMN cells will now have super high internal resistance, so a 11s pack with modern cells will be a very significant improvement.

 

[lnanek]

Personally, I just leave the old Bionx battery alone except connecting the negative wire to the new battery (to establish a common ground). Then I just connect the new battery to the motor. Currently running a 20Ah 52V battery on a Bionx motor hub that way. The Bionx battery just powers some DC-DC converters it has internally for the electronics with this setup, so isn't stressed.

It's true I started with one of those 36V rear rack Bionx batteries with a BMS as well AFAIK, though. Never had something old enough to not have a BMS. Later I replaced that Bionx battery with a 48V Bionx downtube battery from a Grace Easy.

Original motor I got for free with a broken torque sensor:

Original 36V battery I got for free:

Grace Easy 48V battery someone wanted to get rid of because it was beeping and original G2 console and throttle I got for free:

Current 52V battery just connected to motor except for negative wire to the Bionx battery (blue arrow):

I can actually pop a fuse into a fuse holder on a positive wire to connect the two batteries through an ideal diode as well, but I've never gotten the 52V battery low enough for the diode to activate .

Latest project is trying to figure out if I can get a CycleAnalyst to read a magnetic PAS wheel signal and output an analog voltage similar to a throttle signal on this torque sensor connector to control the Bionx motor through PAS:

I've heard some of the old bottom bracket torque sensors Bionx was compatible with used to output 2.5V +/- something, for example. CycleAnalyst should be able to be setup to output a throttle signal starting from 2.5V instead of the normal hall sensor range of 0.8V-4.2V...