MG Drive Unit Reverse Engineering

[Jack Bauer]

One of the big projects I've worked on this year has been the MG drive unit. I'm not 100% sure which exact models and years of MG vehicle use this exact unit but am fairly sure the newer ZS and 5 are amongst them. It also "look" like some of the other drive units MAY use a similar control board but this has not been confirmed as yet.

I'm pleased to say that the V2 OpenInverter board now runs the drive unit in full FOC closed loop mode on the bench. I also have purchased a 2003 Volvo V70 to use as a test bed.

Anyway, for those interested here are some links and videos:

Github repo with lots of info: https://github.com/damienmaguire/MG-EV-Inverter

Videos :

[Jack Bauer]

Guess this was a giant waste of time then...

[Uppertown]

Guess this was a giant waste of time then...

I think it's an idea who's time will come, it's a neat unit, almost an electric diff it's so compact and I'm seeing plenty of MGs on the road so they should soon be plentiful and cheap at the breakers. Perhaps it will take off when we all come out of hibernation in the spring.

[Tomas]

What kind of power does this driveunit make?

[steveknox]

Do you have some basic dimensions for the drive unit? I'm wondering how easily it would fit in the subframe of a RWD car.

[vitecd]

Can I get the firmware, please?

[johu]

https://github.com/jsphuebner/stm32-sine/tree/MG_DU

Binary here, need to log in to github to see it https://github.com/jsphuebner/stm32-sin ... 5956937954

[Jack Bauer]

Thanks is the word you were stuck on.

[Beggernator]

I will say thanks. Have been looking at the rather attractive prices for the mg units and it's nice to see you have worked your magic again on getting things spinning.

[CMARAMLeaf]

This is fantastic! Lots of implementation possibilities from my point of view at least. I’ve been trying to figure out if it’s possible to make the version used by ram work in my truck. Looks like they’re quite similar.

[LRBen]

Scanned a drive unit today. From an MG ZS

Model is here:
https://grabcad.com/library/2017-2020-m ... ive-unit-1

[Jack Bauer]

So as I have never sold a single MG board and have given away the few boards I have in stock I decided to add all Kicad sources and production files to the GitHub repo here : https://github.com/damienmaguire/MG-EV- ... /tree/main

[crasbe]

I started a wiki page about the Drive Unit: https://openinverter.org/wiki/MG_MG5_Drive_Unit
It is very empty still, so if anyone wants to add some information, feel free

Yesterday and today I started to build a replacement for the funky parking lock actuator that is realized with a tree phase motor in the original application and a dedicated controller.
My plan is to replace that with a watertight NEMA 23 stepper (not the one in the picture, Beff Jezos didn't deliver it yet).

Hopefully this Drive Unit will gain some attention once Damien starts the V70 conversion and people notice it. It's a really nice, compact unit but yet very powerful.

[arber333]

I am late to the party, but i stumbled over some wiring and service information online that might help ...
https://openinverter.org/forum/viewtopi ... 789#p89789

[crasbe]

You can actually get access to all the MG service material for a couple of Euros for an hour. That is long enough to download all schematics, service manuals etc.
Only the parts catalogue can't be accessed unfortunately.

[Mouse]

Having obtained one of Damiens hugely popular MG ZS V2 Logic boards and lowballing a MG ZS inverter on Ebay thinking it was a perfect compact inverter solution for a large motorbike. I have instead successfully proved to myself there is more than one variant of the MG ZS inverter module. So to make the best of a bad situation I've compared them as best I can without getting the oscilloscope and volt meter out to see how internally different they are.

By visually inspecting Damiens MG ZS IGBT inverter driver (Left) and the one I have (Right) there are striking similarities and a few of subtle differences between them.

Obvious Similarities
Same shape but different sized PCB and mounting hols.
Same main interconnect cable & connector.
Same raiser cable from IGBT board.
Same IGBT Module : FS820R08A6P2B
Same Gate driver : MC33GD3100EK
The overall layout of the driver chips and isolation power supply transformers is very similar. As is their supporting components.
The driver for the AC power drive for the isolation transformers (8 pin chip and two power components, ) looks about the same but on the apposite side of the board.
The 5 pin under board component (Lower Right) and supporting components is present.

Obvious Differences
There is a number of absent / not fitted TVS / snubber type components on both high and low side drivers but the location of those vacant component pads are similar.
The riser interconnect connector is located on the opposite side of the board but is the same number of pins.
Similar 12 pin connector to motor resolver but uses separate connector and cable from the logic board and is routed internally to inverter / motor housing and not brought out on the main loom via the main connector for an external connection to the motor resolver.
There is a 16 pin device missing but there is a 8 pin device. Both located in the HV discharge resistor area but I've not looked at their part numbers or function any closer.

I'm left wondering if they are functionally very similar and the work Damien has done on reverse engineering and designing the MG ZS OE logic board can be reused simply by re-arranging the layout to fit the variant inverter with minimal changes or further reverse engineering effort.

[Jack Bauer]

It's worth plugging it in for a test for sure. Given the same driver chips the coms is likely the same which iirc was the longest part of the project as the full datasheet is behind some nda nonsense. Oh and yeah I recognise the dc link sensing setup. They use a spare analog channel on low3.

[Mouse]

I'd like to have a sanity check on some of the main voltages and signals on the interconnect cable before doing that.