Dual Motor Question

[death by bacon]

So I've inherited some spare parts and was wondering if this dual motor setup is possible:

Rear Hub
250w Motor
36V Battery 15ah
15A Controller

Front Hub
1000W Motor
48V Battery 12ah
30A Controller

Can I make a splitter for the Throttle and the PAS and connect them to both setups? Am I gonna catch on fire and go to heaven? If it works, are there any caveats or dangers/things to watch out for?

TLDR I want to use 1 throttle and 1 PAS to control 2 hub systems (front and rear) with different voltage and amperage

Thank you

 

[E-HP]

You could run both, but it's more than likely, one motor will be doing virtually all the work at any given time. With one throttle, the throttle will be covering a range of 0V-36V to the motor for the rear, and 0V-48V for the front. Each electric motor has a motor constant that determines how fast the motor spins for each volt provided to it. That's what it means when you hear folks mention a fast wind motor or slow wind motor. Unless you know the motor specs, you may need to test each motors to approximate their motor constant (kv rating). You may or may not be able to have both motors contributing over their full range using the voltage splitter that you are contemplating, but probably not.

The PAS can't be split, since it's a digital signal. You didn't mention if both controller have the ability to adjust PAS assist levels, but there's likely not a way to feed both controllers the same PAS input and have them provide the right voltages to the motor for their RPMs to match over the full range, or maybe not for any of the range.

If you want to invest some $, then you could get a cycle analyst, use it to control PAS (and convert it to a throttle output), then use the voltage divider, which could work if you're lucky. I'm guessing with a couple of feedback loops, you could create/program a solution using Arduino if you're into that.

I don't know for sure, but I believe there are other requirements for getting into heaven than dying in an ebike fire.

 

[fill]

Or build 2 bikes one with greater range but a lower top end speed and the 2nd for shorter urgent dash runs Remember you cant have too many e-bikes.. just not enough room in the garage to keep em all

 

[Chalo]

Remember you cant have too many e-bikes.. just not enough room in the garage to keep em all

/Living room

/Bedroom

Bathroom not recommended due to condensation issues.

 

[E-HP]

/Living room

/Bedroom

Bathroom not recommended due to condensation issues.

Plus you don't want regen anywhere near a toilet.

 

[Chalo]

The PAS can't be split, since it's a digital signal.

I'm not so sure about that. It's still just a Hall sensor signal, inherently analog at the sensor level. I think if you connect signal and GND to both controllers, and +5V to only one controller, just like you should do with a split throttle, then both controllers will do whatever they do with a PAS signal.

 

[E-HP]

I'm not so sure about that. It's still just a Hall sensor signal, inherently analog at the sensor level. I think if you connect signal and GND to both controllers, and +5V to only one controller, just like you should do with a split throttle, then both controllers will do whatever they do with a PAS signal.

Yes, but I mean he can't proportionally split the signal like he can with an analog throttle signal/voltage.

 

[amberwolf]

Yes, but I mean he can't proportionally split the signal like he can with an analog throttle signal/voltage.

Sort of irrelevant, since all the PAS does on 99.9999% of systems is tell the controller to turn on and drive the motor at the full amount for the selected assist level****. Not really any way to get a proportional response out of that regardless of how you were to split the signal (like using a flipflop, coutner, or other digital logic to divide the frequency of the pulsed signal, etc).


****amount= whatever that controller's assist level setup is designed to modulate/limit: speed, "torque", or some more complicated combination thereof.


If it was like the Cycle Analyst or any other Cadence-PAS control scheme that actually varies output based on the cadence (pedal rotation speed), then you could "split" the signal using either an MCU (arduino, PIC, Rpi, etc) or PWM hardware (555) or logic gates/counters/etc, depending on exactly how the specific PAS sensor works and what signal the controller's PAS input is designed to accept. (there are several different potentially incompatible types of PAS sensor signals).


The "simplest" (quickest to setup/wire/get working, without having to design and build and code things) way to split a PAS cadence signal, to actuallly proportionally control different systems on a 2WD, is to use a CycleAnalyst v3 from ebikes.ca on each controller, and use the same PAS signal (and same throttle signal if you're using a throttle too) fed into both. (The throttle and PAS no longer go directly to either controller)

Then setup each CA as needed to make that system do what you want it to do in response to the inputs. That can even include more response by one to the throttle, and less to the PAS, and the opposite by the other system.


It's more expensive to use the CAs to do this...but for any random set of hardware, it's probably the fastest easiest way to do that.

If you can buy specific hardware to create a setup, then there are a number of open-source firmwares you can flash onto various controllers (lishui, kt, etc) to directly give them similar capabilities.