Made good progress on the CV axles this week. Have fully dismantled and cleaned the outer Roadster CV joints, and the inner CV joints on the BMW i3 axles. The BMW end of the axles looks fairly straightforward with a set of 32 splines, but a potential issue is that the inner race on the Roadster CV ...

A bit off-topic from BMW i3 inverters, but for anyone needing to take the inner CV joints on the i3 motor apart, the cage, inner race, and balls are retained by an internal snap ring that runs around the inside lip of the housing, indicated by the arrow on the image below. Easily removed with a ...

Offside front subframe clamp now complete and motor fully supported. The tube coming off the motor mount ended up 15mm lower than expected so had to modify the top half of the mount to move the bushing carrier down. The base of the mount is also a bit close to the subframe seam.

Have since realised ...

Offside frame done and everything fits reasonably well, though some of the bolts are a bit tight bringing it all together. Going to make a few tweaks to the CAD a mm here and there to improve the fit in case anyone else decides to build one.

Removed the skateboard that the drive unit's been sitting ...

Started welding the motor mounting frames this weekend. The main crossbar that picks up the two existing rear engine mounts is complete, and the driver's side frame that picks up the front engine mount and bolts to the right hand side of the i3 drive unit is almost done. Just a couple of corner ...

Designs for the driver's side engine mounting frame are now done after two month hiatus. Have built in a mix of steel and 3D printed parts to confirm fit. Current plan for the offside front mount is to bolt a clamp around the subframe to avoid having to weld anything on, finalising the design for ...

Using CAN signals from the SAM unit, which already reduce the torque requested from the motor based on the wheel speed sensors if the ESP is enabled. Still working on the engine mounts, once those are done will get back to the CAN testing. Pete9008 has some good insights here: https://openinverter ...

The plan for the driver's side motor mounting frame is to run a transverse tube between the two rear engine mounts and then a longitudinal bar to the front engine mount, picking up the three bolt holes in the motor housing. Have started cutting the steel parts, will post pics as it develops.

The ...

Updated estimate of max tractive force on dry asphalt is 4300N (1270Nm of driveshaft torque) based on the front/rear weight distribution of 44%/56% (max axle loads of 465/610kg) and assuming weight of 878kg from the car's operating instructions (includes allowance for engine fluids and 75kg driver ...

Sounds good!

Bear in mind that the motor mounts see driveshaft torque reaction not motor/engine torque. The higher ratio of the Roadster box 1st gear balances things up a bit and the mounts will have been designed to handle that. The i3 is likely still higher but probably not by enough to worry ...

Janosch was down this week to check in on progress so we started setting up hardware to get started on sorting out CAN bus communications.

Have ordered a spare MEG (ECU), mainly to salvage the connector for a replacement ECU build to link the roadster's SAM unit to the openinverter and throttle ...

3D printed mockup of the offside engine mount to check geometry and bolt spacing. Planning to get these laser cut from 3mm steel then welded together with steel standoff tubes. Driver side mount is more complicated.

Got the rear subframe and dedion tube back from the paint shop a couple of weeks ago, now reassembled in typical driving position to start work on the motor mounts.

The clearance front and rear is quite tight, so also had to remove a tab/lifting eye from the back of the transmission housing to ...

Measured 4.7K across the pull-down resistor on the mosfet gate today, so will be swapping the series resistor on pin 35 of the Harwin connector for a 100 Ohm. That should limit current to ~50mA while minimsing voltage division.

johu wrote: ↑Sun Apr 28, 2024 4:20 pm I should check my board and find out why it works without the patch. Where on the board is that part of the circuit?

It is located on the underside of the gate driver board, tip of the blue arrow below:

Upon reflection, it looks like there is a pull-down resistor on the mosfet gate, so might reduce the gate series resistor to 100R to avoid creating a voltage divider that reduces the gate voltage too much. Will pull the gate driver board out again next weekend and try to measure the pull-down ...

This is the final fix I've implemented after testing.

Pins 33 and 34 on the Harwin connector are both connected to the 5V 500mA output on the openinverter board. Added a 10K resistor between Pin 34 and 35 to provide power to pin 35 and the mosfet gate on the gate driver board.

Possibly it would ...

Reviewed motor position in the subframe again today. Current thinking for the motor mounts is:

-Run a box section across the two rear mounts
-Run another box section from the rear box section to the forward engine mount, with a laser cut plate picking up the various mounting holes on the side of ...

Today I ran the motor again, this time powering pin 35 on the Harwin connector with 5V from the openinverter board via a 10K resistor and registered no current draw on the multimeter.

Will plan to use this setup going forward as seems safer to use the regulated power supply on the openinverter ...

With the motor back in the subframe and the aircon mounts out the way, it now appears there's (just) sufficient space for it so will be getting on with designing/fabricating the mounting frames.

Great work CJW, looks like we've managed to cobble together a working inverter! I feel it would be a good idea to put some kind of gate resistance inline (10R?) but probably not expressly necessary.

Interested with respect to the parameters, I thought that at some stage there was an i3 variant ...

Air conditioning compressor mounts removed...

Finally got the motor spinning successfully with the drop-in board so next step is to figure out how to fit it in the sub-frame and get a set of mounts made. It's quite a tight fit, hoping to be able to get everything in without having to modify the cross-frame to create more space. Aware that the ...

Parameters used for the successful bench test attached. Notes below:

-firmware version 5.32.R-foc, with Johanne's code mod applied separately to disable err_out pin that was preventing SPI comms
-24V test voltage from a pair of lead acid batteries
-no contactors, so parameters for precharge and ...

Had a go at tracing pin 35 on the gate driver board and looking up datasheets to get a better idea of what's going on here with a view to hopefully confirming that a 12V supply to this pin is correct. Information below with the caveat that I have a fairly basic understanding of electrical circuits ...