Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

Had another look at the connector and I think it is OK to reuse. Also decided to leave all the connectors off during the initial build as they are difficult to remove without damage, difficult to replace and I don't know if the board actually works yet! Once the board is tested Ill hand solder them on. The soldering wont be quite as neat as reflowing them with the rest of the board but it seems a safer approach.

The PWM frequency on the F4 looks like it will be either 5.1kHz or 10.2kHz due to the increased core clock frequency. I would like to run it at 10.2kHz but not sure the Prius inverter will cope, any thoughts on this?

Also planning to change the way desat detection works. Given the Prius inverter seems so good at protecting itself I'm inclined not to immediately disable PWM (not a great idea if above base frequency) if the MG fault line goes inactive. Instead I'll limit the torque request and light the ECU error light. Again, any thoughts?
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by johu »

According to Damien Prius inverters rather like 5 kHz. But you can try that. Your control loop can still run at double that and adjust the turn off time.

You can also run any PWM frequency you like. I just chose powers of 2 to be able to shift rather than divide. Also the resolver frequency is tied to PWM frequency on the F1. You can loose all those constraints when doing a custom firmware.
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

Thanks. Is there any reason why 4.4 is always recommended for the Prius inverter rather than 8.8kHz? Was wondering whether the increased switching losses might cause power dissipation problems?

The control loop runs at twice PWM freq and the PWM is reloaded at the top and bottom count. Re the freqs they come from trying to keep the reload register to a power of 2, not essential with float support but still much neater!
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

Trying to get a handle on the effect of PWM frequency on efficiency, should really add the code to the simulator to get some accurate data but can't be bothered right now so some guestimates and rough calculations will have to do instead. Say a cruising load of 10kW and say this is equivalent to an average 100V drop across the IGBT and 100A through the IGBT during switching and a switch time, to the average point, of 1us, then that would mean that each switch event dissipates around 10mJ.

If the PWM is running at 4.4kHz then we have 4400 x 6 (IGBT) switching events per sec or 264W, this seems reasonable, 97.4% efficiency.

If we run the PWM at 8.8kHz then this would go up to 528W or 94.7% efficiency.

So doubling the PWM frequency would reduce efficiency by around 2.5% or a reduction in range from say 60miles to 58.4miles. Not huge but not worth doing if there is no real benefit.

Note - the above is probably an overestimate of the losses as all the phases won't be switching high current at once so the impact on efficiency is probably lower.

At the low power levels above power dissipation in the inverter is unlikely an issue. However if running at peak power of 100kW the power dissipated would be 2.6kW at 4.4kHz or 5.2kW at 8.8kHz. This could well start to be a problem depending on what the thermal impedance of the IGBT to coolant is. If we assume that a 100C increase is acceptable and that the load is equally shared then an impedance of 0.12C/W per IGBT module would be needed - definitely possible (commercial IGBT modules seem to be about half this for junction to the base) so should be OK at 8.8kHz PWM.

Given the low inductance of the Outlander motor I think running at a higher frequency would be a benefit. 6.25kHz works nicely for the current and angle sampling (a mid PWM trigger would allow 40us computation time before the next reload which is the max latency I'm aiming for) so I'll start with that. If there is still too much current ripple I'll increase the PWM frequency a bit more. This does mean losing the power of 2 for the reload value so instead I'll normalise all the Uq/Ud values to 1.0f and then scale them just before writing the value to the PWM registers.

Edit - writing the above has made me realise that rather than using the spare channel on the PWM timer to trigger the resolver and motor current sampling I should slave another timer to the PWM timer reload and use the output from that to trigger the measurements. This would remove the need to have the sampling at the midpoint, allow finer control of the sample point and also make the latency totally independent of PWM frequency.

Edit2 - When starting the above calculations I was just thinking about the effect of PWM freq on inverter dissipation so ignored IGBT resistive losses (don't change with PWM freq so not relevant) but then forgot to include them when calculating the power loss at higher power levels. I'd guess the IGBT resistive losses could easily be a kW or two at 100kW load so cooling is likely to be an issue with the 8.8kHz PWM.

Edit3 - Just had a look at the oak ridge report and the inverter efficiency varies from 99% to 92% (at 500V bus voltage) at high currents and this ties in reasonably well with the above numbers.
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by johu »

You surely got your math at hand :) The losses sound a bit much though, just from experience.

The double call per period doesn't depend on the period being a power of two. You just get one call each time the counter changes direction, if so configured.
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

johu wrote: Wed Dec 28, 2022 7:24 pm You surely got your math at hand :) The losses sound a bit much though, just from experience.
I tend to guess high and round everything up when doing sums like this so that doesn't surprise me. Would be nice to be able to run the PWM a little faster, even if just to get the whine outside the audible spectrum ;)

johu wrote: Wed Dec 28, 2022 7:24 pm The double call per period doesn't depend on the period being a power of two. You just get one call each time the counter changes direction, if so configured.
Yep, get that. The power of 2 just seems a 'nice' reload value but going to bin it and instead use whatever gives the frequency required.
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

Came across a list of OEM inverter frequencies while trying to find details of the Outlander inverter. Unfortunately it doesn't list that but it does cover a lot of other models so thought it worth posting a link to it :

https://e-nvh.eomys.com/what-is-the-swi ... wertrains/

Not sure of the accuracy but based on it the Prius and Leaf seem to be the exceptions running at 5kHz with all the others being 8-10kHz.
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by ChristerE »

Cool to see that there are several people who are interested in converting a Smart Roadster to electric operation. Have had a hold up in my building for 1 1/2 years.
My build consists of Smart Roadster 2003 and motor with inverter from a VW ID.3 have assembled it in place. The next step is to communicate with the inverter, where the plan is to use the power transistors from ID.3's inverter and openinverter.org Brain Board Rev 3. What remains is the adapter board for the IGBT transistors.
An early picture of the engine installation:
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

ChristerE wrote: Thu Dec 29, 2022 7:44 pm Cool to see that there are several people who are interested in converting a Smart Roadster to electric operation. Have had a hold up in my building for 1 1/2 years.
My build consists of Smart Roadster 2003 and motor with inverter from a VW ID.3 have assembled it in place. The next step is to communicate with the inverter, where the plan is to use the power transistors from ID.3's inverter and openinverter.org Brain Board Rev 3. What remains is the adapter board for the IGBT transistors.
An early picture of the engine installation:
Looking good :) Are you going to do a build thread, I'd be interested in seeing more details?

The motor looks like it fits well, the motor being forward of the driveshaft means that it clears the watts linkage and keeps the weight towards the middle of the car which is good. What are you plans for batteries and where are you going to put them? Has anyone reverse engineered the ID3 IGBT driver interface?

A little more progress on mine. All the bits are sorted out ready to hopefully assemble the board tomorrow. Have revised the terminal class in the firmware so that it will cope with the unidirectional RS485 comms (removed echo characters and added transceiver receive/transmit switching). Also ordered a USB/TTL to RS485 module so that I can talk to it from either the PC or ESP32.

Also the Heltec board that I'm hoping to make a keyfob remote out of turned up today. Only had a quick play with it but fairly impressed so far (not used the RF side just messing about with the display); the Arduino support and examples seem to be really good. This is where I'm up to with it (ignore the heat/cool icons and temperatures - I know they don't make sense!):
fobRemote.JPG
Can't decide whether to keep the Roadster graphic or just use it as a text display. The graphic is nice to have but it does take up a lot of display real estate making the text a bit on the small side.

I also have the LoRa transceiver for the car end and a spare Nucleo-64 (STM32F103) to hook it up to for testing so hopefully have the RF side working soon too.
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by ChristerE »

Pete9008 wrote: Thu Dec 29, 2022 10:00 pm Looking good :) Are you going to do a build thread, I'd be interested in seeing more details?

The motor looks like it fits well, the motor being forward of the driveshaft means that it clears the watts linkage and keeps the weight towards the middle of the car which is good. What are you plans for batteries and where are you going to put them? Has anyone reverse engineered the ID3 IGBT driver interface?

A little more progress on mine. All the bits are sorted out ready to hopefully assemble the board tomorrow. Have revised the terminal class in the firmware so that it will cope with the unidirectional RS485 comms (removed echo characters and added transceiver receive/transmit switching). Also ordered a USB/TTL to RS485 module so that I can talk to it from either the PC or ESP32.

Also the Heltec board that I'm hoping to make a keyfob remote out of turned up today. Only had a quick play with it but fairly impressed so far (not used the RF side just messing about with the display); the Arduino support and examples seem to be really good. This is where I'm up to with it (ignore the heat/cool icons and temperatures - I know they don't make sense!):
fobRemote.JPG
Can't decide whether to keep the Roadster graphic or just use it as a text display. The graphic is nice to have but it does take up a lot of display real estate making the text a bit on the small side.

I also have the LoRa transceiver for the car end and a spare Nucleo-64 (STM32F103) to hook it up to for testing so hopefully have the RF side working soon too.

I will come up with my own build thread in the future when I start building again.
The battery is planned to be in the front trunk, possibly there is a little space behind the driver's seat. Thinking of looking for the control signals for the IGBT interface on the existing Inverter.
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

ChristerE wrote: Sun Jan 01, 2023 4:31 pm The battery is planned to be in the front trunk, possibly there is a little space behind the driver's seat. Thinking of looking for the control signals for the IGBT interface on the existing Inverter.
This may be useful, it's a spreadsheet for calculating the front and rear weights for the Roadster (coupe version) based on corner weights I measured. It gives a spare weight (before exceeding Smarts axle weights) at the front of only 42kg which realy limits what you can put in the front in terms of batteries.

Most of the spare weight, after removal of the engine, gearbox and fuel tank, is at the rear. I'm hoping to fit the battery in the space between the rear subframe and the monocoque (looks possible on the side profile view but not actually taken things apart yet to have a look). Do you have any measurements from yours in terms of the space available there (particularly the height at the front where the fuel tank was)?
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

Quick progress update - not got the logic board board built, coordination is a bit shot at the moment so will have to wait a few more days.

I have got the LoRa board working. No pics though as it doesn't really look any different to the above but it is now correctly interrogating a remote 'car' node and then displaying car live data. A button press wakes it to request and display data, another short press updates the data and a long press triggers a preheat on the car and also updates the displayed data. Power consumption of the fob node is around 30mA when active and only 14uA when sleeping so even a 100mAh battery will give an 8month battery life and then it can be recharged by plugging into a USB port.

The 'car' node is currently based on a STM32F103 eval board and I've forked a driver repository for the LoRa transceiver and ported it over to the eval board (on my github if anyone is interested). This will eventually be developed into either a stand alone CAN bus node or be integrated into the VCU.

Still need to add security features to it (pre shared key to encode command data) but apart from that it's done. :)
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by mjc506 »

Nice! I really like the LoRa ideal, might have to steal it :)

wrt USB charging, how about a QI charge 'receiver' on the fob, and the charger base in the car somewhere? Although that'd sort of 'require' keyless ignition I guess.
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

mjc506 wrote: Tue Jan 03, 2023 10:35 am Nice! I really like the LoRa ideal, might have to steal it :)
Feel free :)

Quite impressed by LoRa. Having looked at RF stuff in the past and found it hard work (code for packet detection, noise rejection, NRZ/manchester encoding, modulation schemes,etc), and disappointing performance when it does work, LoRa is a breath of fresh air! All the functionality embedded into the transceiver reduces code to basic setup and then just writing packets to the chip at one end and then reading them out the other. In terms of performance it is also better than I expected - set to around half max Tx power and without antennas at all it works fine on the bench, with an antenna on just one node (I only have 1 antenna at the moment!) it works up to 10-15m (including through block walls in the house) so it looks promising for decent range outdoors with proper antennas on both nodes.

For anyone interested below is a summary of my findings while researching the LoRa options:
  • There are two versions of the modem chips, the SX126x and SX127x. The SX126x is newer, has 2dB more output power and uses around half the power. The SX127x has better Arduino library support. Both should have similar range/performance. I went with the SX126x due to the lower power and had to port a library over to the STM32 (see https://github.com/Pete9008/SX126x)
    Edit - The two should be completely compatible with each other so can be mixed on a network.
  • For the key fob end there are options based on the ESP32 and on the ASR650x. I went with one from Heltec (CubeCell series) that uses the ASR650x which integrates the SX126x modem and a PSoC 4000 micro (ARM Vortex M0 based) due to the much lower power consumption in both active and standby modes. Libraries are available for this on both Arduino and PlatformIO which have a very good set of examples covering most uses cases.
  • For the car end I struggled to find a transceiver module that uses the SX1262 (868MHz UK frequency version) and was easily available and ended up using the LR62E available from Digikey (https://www.digikey.co.uk/en/products/d ... E/13174291). The documentation isn't great and it needed a couple of library tweaks to get it to work (status message response and TXCO control) but seems to now work fine with the modified library.
  • Planning on using this antenna on the fob (https://www.digikey.co.uk/en/products/d ... -T/8593246 as it is very compact, not sure how much it will impact on range compared to a proper antenna though (specs say it should compare fairly well but not convinced).
Have now added AES128 encryption to the code so that the RF data looks completely random and the fob and car are also paired by the shared key (although what should have been a simple job took all day due to brain fog!) so going to call that done. Need to design an ABS case for it now.
mjc506 wrote: Tue Jan 03, 2023 10:35 am wrt USB charging, how about a QI charge 'receiver' on the fob, and the charger base in the car somewhere? Although that'd sort of 'require' keyless ignition I guess.
I like the idea but not sure it is worth it. A 300mAhr battery should fit in no problem which would give a battery life of almost 2years (assuming 10 operations per day) so the extra complexity doesn't seem justified. Thinking a little more though it would then have more power available and so could be used for keyless entry - just need to figure out how to bypass the Roadster immobiliser!
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by mjc506 »

Awesome info, thanks :)

Oh yeah, Qi charging totally overkill, the main advantage is that it'd "always" be charged so long as the car was used occasionally. I guess on the car side, a "signal strong + Qi charger drawing power" might be a sufficient 'ignition' signal but bypassing the imobiliser sounds... "fun"...

Feature creep hahaha
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

mjc506 wrote: Tue Jan 03, 2023 1:27 pm Feature creep hahaha
:lol: Tell me about it!

Came across the module while browsing the web a while ago and thought it worth ordering while available with no intention of doing anything with it yet. It turned up earlier than expected while I wasn't feeling up to doing anything too involved and thought trying it out would be a quick and easy, but still vaguely productive alternative. Feature creep then caught me out!
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by marcexec »

Pete, I think the LoRa remote keyfob is brilliant - maybe it deserves it's own thread?
(obviously to make it easier to steal - the idea, not the car! :))
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

marcexec wrote: Tue Jan 03, 2023 3:53 pm Pete, I think the LoRa remote keyfob is brilliant - maybe it deserves it's own thread?
(obviously to make it easier to steal - the idea, not the car! :))
It's the easier to steal bit that worries me, it's always easier to hack the security on something if you have the source code ;)

In all seriousness no problem sharing the code (I think it's pretty secure and I don't plan on sending anything important over it) but there's not much value in it at the moment. The fob end software is pretty much done and I have the outline of the car end but until the car end is integrated into a VCU, or into some dedicated hardware with a CAN interface, there is not a lot that can be done with it. It's something I plan on trickling along in the background so would expect something usable in 6-12months, maybe start a thread on it then?

The other thing I thought it could be used for, as well as the ability to pre heat or cool, is to be able to boost the batteries to 100%. My understanding is that charging to 100% is only harmful if the battery is then left in that state, if it is immediately discharged then the harm is minimal. Is that correct? If so then the ability to normally only charge to 80-90% to protect the cells but have the ability to boost half an hour or so before leaving could be quite handy on a car with a smaller battery pack?

The only other idea I'm toying with is whether to try and build the PCB from the standard car key fob into the back of the LoRa one so that a single fob can be used to both unlock the car and remotely access it?
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by marcexec »

Well, it depends on what "100%" is defined at, but yes, high voltage for longer duration is a problem.
Charging to 4.20V or so just before leaving isn't a problem.

I always explain that as batteries are based on a chemical reaction high temperature and high voltage accelerate the process (dendrites in this case).
Either is bad, both are very bad, multiply with time. That's why I try to charge my phone to less than 100% & our 2014 Leaf is basically only showing calendarial degradation as it's only charged to 100% (@4.08V I believe) about 10x per year (trips and free charging :D).
Same for the shitty 2012 Leaf modules on the motorbike - 65-70% now (unless some idiot exposes them to water spray from the front wheel).

Some reading on LiFePo, where it's even more pronounced as less calendarial degradation: https://www.powertechsystems.eu/home/te ... e-lifepo4/

BTT, does the BMS accept the 80/100% switch with CAN messages?
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

Thanks for that, confirms most of what I was thinking :)

Still got a fair bit of reading to do to get up to speed on batteries but yes I was thinking that 100% would be 4.20Vish.

Re the BMS it will do - once I've designed it! The plan is to integrate everything I need for the car into a custom VCU. So far my thoughts on it are:
  • Based on a STM32L496 processor (91uA/MHz when running, 2xCAN, 3xADC, 2xDAC, 6xUART, etc).
  • CAN1 - To interface to Smart's existing bus (only active when ignition on).
  • CAN2 - To interface to battery pack, inverter boost/DC:DC processor and charger interface (always active).
  • RS485 - To interface to external ESP32 module for web interface and data logging.
  • LIN bus 1 - 9600baud, I-Pace A/C expansion valve,
  • LIN bus 2 - 9600baud, I-Pace A/C ball valve and I-Pace expansion valve,
  • LIN bus 3 - 19200baud, VAG water heater, AC compressor and AC pressure sensor.
  • LIN bus 4 - spare channel.
  • 4 x PWM outputs - to suit Prius/Auris variable speed aux water pump speed control (inverter/motor loop, battery loop, cabin heat loop and spare).
  • 4 x PWM inputs - to suit Prius/Auris variable speed aux water pump status output.
  • 2 x 3-way water valve control outputs (interface TBD, battery loop mixing and spare).
  • LoRa transceiver - for remote keyfob.
  • Charger Pilot and Proximity connections interface.
  • Interface for external HV DC voltage measurement circuit (MAX22530 based)
  • 8 x 10k NTC temperature sensor inputs (A/C compressor outlet temp, expansion valve outlet temp, cabin evaporator temp, battery water temp, external temp, cabin temp + spare)
  • 1 x switch mode out to drive cabin heater fan motor
  • 2 x PWM out to drive cabin heater blower control module and radiator fan control module.
  • ? x analogue inputs - +12V battery voltage, cabin temp setpoint, cabin fan speed setpoint +TBD
  • ? x 3A? low side output drivers - TBD
  • ? x 3A? high side output drivers - TBD
  • ? x digital inputs - TBD
The idea is that when the ignition is off it will run in low power standby mode (hopefully less than 5mA) and keep an eye on the 12V battery (running the DC/DC as required) and provide a LoRa comms interface. When charging it will act as the BMS, set charge limits and control the battery heating/cooling. When the ignition is on it will manage the contactors, set charge/discharge limits, manage heating and cooling loops, climate control, etc.

Again this is very much phase 2 and is highly unlikely to be in the initial car. I've started on the schematic but it is another trickle it along in the background project. The list above is just to try to get it clear in my mind and if I've missed anything hopefully someone will point it out :)

Edit - changed fan control method above.
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by DkubusEV »

Sounds great 👍
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

Just had a thought re the above, for cabin heater fan control I was planning to build a brushed DC motor controller into the VCU, the trouble it that means routing the high current fan wiring too the VCU and having the heat generating and potentially electrically noisy PWM stuff inside the enclosure and close to the LoRa module, neither of which are ideal.

It occurred to me that I could use a standard off the shelf radiator fan control module, something like this, https://www.ebay.co.uk/itm/255606958284. I think it just has a PWM control input that controls the fan speed and if so it would be ideal and a lot easier to do.

Has anyone used something like this and if so did it work and can you confirm how they are driven?

Now I know everyone is asking why bother with this at all? Well firstly I would like to eventually be able to preheat/cool the cabin which needs electronic rather than manually switched control. Secondly I'd like to convert to climate control rather than manual control an thirdly the Roadster has a notoriously bad heater fan control switch which has a habit of melting both itself and the attached wiring, and mine already has, so it needs replacing anyway!
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by bexander »

Very interesting idea. In the C30 (my other project car) I think uses exactly the controller you linked to. (C30, S40, V50 and C70 uses the same platform, Volvo P1).
In the wiring diagram for my car it looks like this:
CoolingFanVolvoC30.pdf
(32.55 KiB) Downloaded 58 times
And then reading the pinout explanation for the 2.0D ECM pin A:B2:
image_2023-01-07_184426522.png
It shure looks like the ECM is just sending a 12V PWM signal to the fan controller. The fan controller is mounted very close to the fan motor in the car.
I do not have the C30 in the garage at the moment but I still have all parts needed to hook it up and maybe possible to measure the PWM frequency even if I don't have the IC motor and all the other signals to the ECM. Let me know if I should look into this when the car is back in the garage?
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by Pete9008 »

Thank you, exactly what I was hoping to hear.

Don't worry about trying to measure it, without everything connected up, and possibly the engine running, I doubt it will do anything but thanks for the offer.

What would be very useful is which wire colours go to which connector pins?

I'll get a used one on order and give it a try.
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Re: Smart Roadster (with Prius Gen3 Inverter and Outlander Rear Motor)

Post by bexander »

I was thinking that the ECM might send out an PWM signal even if not commanding any fan, but I guess you are right that it will not if the engine is not running.

My module looks very different but the connector looks like it might fit the module you linked to from ebay.
IMG_2212.jpg
IMG_2210.jpg
IMG_2209.jpg
IMG_2208.jpg
So my best guess is
ebay.png
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