[SimonRafferty]

This is something I've pondered for a while! How possible is it to convert a 'modern' car?

I've read several dicussions about whether to try & simulate the sensors on the engine to fool the ECU or to replace the ECU altogether - with no clear winner between the two. Both seem difficult.

I decided to go for a third option! Most critical vehicle systems will work OK without the engine actually running - ABS, SRS, EPAS, Body controls etc. This is important in case your engine stalls on the highway - you still need steering & braking to work properly.

My solution is to insert a CAN Bridge between the original ECU and the rest of the vehicle. Filter out the messages for speed, rpm, engine temperature which may be read by other systems to change their action. PAS usually provides more assistance at lower speeds. ABS only functions at higher speeds for example.

The filtered messages can be replaced with values derived from the EV controllers and injected into the bus. I've done some preliminary work on this on a 2021 Polaris General Although this is relatively simple compared to most vehicles (only one CANBUS, 3 ECU's). My 2005 Range Rover Sport has 3 CAN networks & 16 ECU's. I've reverse engineered (hacked) a lot of that too!

I think a lot of the problem is fear of the unknown, rather than it being technically difficult. It is, though, much easier to convert a stone-age vehicle & not have to worry about all the computer stuff. Reverse engineering takes time, even if you know what you're doing

I probably wouldn't embark on this if it were my first EV conversion. Even though, this is still a challenge. Luckily, I like challenges!

 

[SimonRafferty]

The problem is that you need a working car for generating most of those messages. Many conversions start out de-ICED or are bought as DOA.

If it still has the ECU in place - that will give you most information, even without an engine.

 

[SimonRafferty]

I agree, the current crop of PDM's are really good! That most likely takes care of the BCM side of things. Then you can either replace the dash - or delve into CANBUS to try to control it.
In practice, you still need to add some kind of display for things like cell voltages, temperatures, SOC etc. However, you can buy these pretty much ready built.

 

[SimonRafferty]

What if we took everything out and rewired from scratch? Build a new system that incorporated the the Battery Management System, etc.

It's definitely an option - but it's quite a big job! Modern cars have one hell of a lot of wiring!

The bits that will make it difficult are ABS / Traction Control / ESP, Maybe power steering, maybe Air-Bags, maybe suspension control (less likely).
Most of the above are designed to be fault-tolerant and will continue to work even if the engine is not running / broken / totally missing! That's why I took the approach of leaving the ECU in place to start up the ABS Controller.

 

[SimonRafferty]

is that many people who consider these projects simply don't understand how modern cars work, and the intricacies of all the subsystems.

That's very true. I've worked in this field for a major vehicle system manufacturer - but still find a lot of it bewildering!

It just depends on what you want to do with your time and money.

However, this is a DIY Electric Car forum - so I guess most on here are interested in building rather than buying! For me, I've been looking for an OE EV for about a decade, but still haven't found one that meets my needs! A Cybertruck or the electric F150 are close - but neither are likely ever to come to Europe and wouldn't fit on the roads if they did!