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Because they report voltage, current, torque and RPM (and I trust those values reasonably), I'm able to calculate the kinetic power and electrical power. The difference between those two values should approximate the efficiency of the #startergenerator.
So I quickly threw together a plot of the efficiencies at various RPM and torque levels. Both for the driving and generating mode.
I honestly expected a bit more, but I guess they are more optimized for torque and other factors :D

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A scatter plot of roughly logarithmic curves.
The best one approaching 95% between 1800 and 3800 RPM.
The higher the torque, the worse the efficiency gets. — A scatter plot of roughly logarithmic curves. The best one approaching 95% between 1800 and 3800 RPM. The higher the torque, the worse the efficiency gets.

Same scatter plot, but for the generating mode.
Also pretty logarithmic, and the curves are more clearly defined.

There is a clear dip in efficiency after around 3800 RPM.
That's where the inverter switches from driving the stator with sinusoidal PWM to a simple block commutation. (Further regulation is then done with the excitation current of the rotor, I suppose)

Some points are over 100%, maybe because the data points are being measured during a (slow) acceleration and not steady-state, but idk. — Same scatter plot, but for the generating mode. Also pretty logarithmic, and the curves are more clearly defined. There is a clear dip in efficiency after around 3800 RPM. That's where the inverter switches from driving the stator with sinusoidal PWM to a simple block commutation. (Further regulation is then done with the excitation current of the rotor, I suppose) Some points are over 100%, maybe because the data points are being measured during a (slow) acceleration and not steady-state, but idk.

LeoDJ

@LeoDJ@chaos.social · last year

I spent many dozens of hours losing track of time in #Ghidra (I swear, it's worse than #Factorio)

Until I had figured out the #CAN message handling, signal parsing and where and when which #DTC codes get set.
With that knowledge I could figure out, slowly but surely, what the #startergenerator needs to run.
Even #FBS4 was pretty trivial to circumvent (a single 1 written to the right memory location via #XCP)

And after implementing the ~25 CAN messages in my STM32 code I finally got this today:

LeoDJ

@LeoDJ@chaos.social · last year

There's still a lot left to do.
I need to implement the #XCP stuff into the STM32 firmware, so it can run the #startergenerator stand-alone.
Stuff like:
- Checking the firmware version on the ECU, so it doesn't poke the wrong memory address
- Reading and parsing the status of the motor
- And actually controlling the motor properly instead of just sending it a hardcoded 1 Nm torque request :D

And then also cleaning it up enough, documenting and testing it thoroughly, so it can be published.

LeoDJ

@LeoDJ@chaos.social · last year

We also did a max RPM test of the #startergenerator using one of @patagona's rescued Pylontech batteries, because the 20A of my 1kW lab PSU weren't enough :D

I set the torque limit to 0.7 Nm (out of 55), no RPM limit and let it rip :D
It reached a peak of 43A (~2kW) at the end of the acceleration, settled at 25A (~1.2kW) and reached a peak RPM of 13400.

It was a bit scary tbh :D
(Not sure if the video accurately captured the sound it made)

(Pylontech thread: https://chaos.social/@patagona/113149877881417810 )

LeoDJ

@LeoDJ@chaos.social · last year

The general control loop is also pretty impressive, the engineers at #Bosch SEG definitely did their job well.

The lowest limit I can set is 6 RPM and it runs buttery smooth.

And it has insane amounts of torque. If you hold the pulley really tightly, it slips out of most strong hands at around 6-7 Nm (as reported via the CAN status messages).

This will be really fun once put into some small vehicle :D

(It can also recuperate really well, but can't run in reverse at all)

#startergenerator

LeoDJ

@LeoDJ@chaos.social · 4 weeks ago

Today, I've built a "temporary" test stand, so I can hopefully test the (thermal) performance of the #startergenerator in the coming days.

It was a welcome excuse to finally dabble in some metalworking again :D

Also, those belt tensioners really need quite some force.

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Two starter generators, bolted to square metal tubing, connected with a belt. The left starter generator features a belt tensioner.

Same setup as the last picture, from another angle

Cinematic photo of a single starter generator, seemingly "balancing" on a single mount (but actually being held by the bolt).
Shot by @twizzarak@chaosfurs.social — Cinematic photo of a single starter generator, seemingly "balancing" on a single mount (but actually being held by the bolt). Shot by @twizzarak@chaosfurs.social

LeoDJ

@LeoDJ@chaos.social · 5 days ago

Finally got to do some dyno runs with the #startergenerator this week.

As I'm able to vary many factors (target drive torque, generating torque, RPM and time), I tested many variations.

tl;dr: They definitely deliver on their 12.5 kW promise, but the stator gets hot quickly, especially at low RPMs and high torque.
I couldn't test the full 55 Nm, only up to 36.6 Nm, as that's the generating limit.

I'm still amazed by the engineering of those things. So much data and protections :D

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Manawyrm | Sarah

@manawyrm@chaos.social · last month

@LeoDJ Did you ever try to use it as a generator? I happened to stumble across a half-broken gasoline power generator, and am wondering if I should try to put one of these into it.
The starter could also act as a starter for the motor, giving it a super fancy extra feature...

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