Electric vehicles (seasonal rambling) Featured

When you design something, you draw boxes around bits of it. There is a philosophy and an architecture behind it.

The idea is, you don't EVER want 400V on the left, to show up on a failure, on any component (in the cabin or even under the hood) on the right.

+-------------------------+ +-------------------------------+ | 400V battery | | 12V Battery | | |---- OptoIsolators? ---| | | Inverter/Charger/Regen | | Lighter for your smoke | | | | Car radio | | Electric Motor(s) | | ContactorToEnable400VSystem | +-------------------------+ | | This box waterproof!!! | Computers + Sensors | Orange colored big wires +-------------------------------+ to impress Fire Department!

You don't want a fault from the HV system, to show up inside the car. If the 400VDC to 12VDC buck converter you designed to drive the lighter socket develops a short from primary to secondary, a person sticking their finger in the lighter socket could be electrocuted.

The "box" on the left has to be water-tight, so first responders jumping into a river to rescue your electric ass, are not the recipients of a 400VDC shock. DC is a bastard for your muscles. If a technician was working on a BEV and shows signs of electrocution, I would kick him with my safety boot -- never reach out and rescue someone with your two bare hands if you expect to be able to escape or let go. The DC through your muscles can keep muscles clenched.

This is how the other day, there was some video from a city that just had a flash flood. One car driver had water all the way up to the door glass on the car, and right up past the front grill and at bonnet level, and he drove (still under power) from the flooded street into a less flooded parking lot. That is only possible with an electric car.

While you can fit a "snorkel kit" to ICE vehicles, usually the intake on a snorkle kit is a pipe rising up the side of the vehicle, demonstrating to you as the driver, what your limit on snorkel operation is. The car driving with the water up to the glass, that would be too high for a snorkel terminating under the bonnet metalwork. A snorkle kit has a valve on it, such that if the vehicle rolls or tips, the potential for water to enter the pipe can be stopped, before the engine ingests it. But the car in the video, had no such pipe up the side. There were no bubbles for exhaust coming from the back, either :-) That wasn't an ICE.

When you drive a BEV, that's a modern marvel. And it's a marvel for all the things you cannot see and did not think about.

I don't know a thing about designing cars, but I can certainly think of some boxes to add to such a *dangerous* piece of kit. Think how much effort it takes, to prevent 400V from ever contacting anything in the environment... If you smash the vehicle into a brick wall, I expect the contactor fails open, but I don't know if the water tight integrity of the battery box modules can be guaranteed. There will still be some situations where the Fire Department are in mortal danger on a river rescue.

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You have to learn all about this stuff, to keep customers safe.

When you design PCBs for the computers in cars and the like, part of the review of your design, includes checking creepage and clearance around interfaces that deal with nasty voltages. More of your time can be spent in a review, impressing your peers with the care you've taken, than with the computer parts that really needed review. So when as an engineer, you work on s*it like this, that consumes big bites of your time. You have to read up on the topic, and be good enough at it, to defend yourself in an audience of experts.

It's like when you make an idle comment about "Time" in a USENET group (maybe you were making a joke about Time), and a Time Lord shows up :-) Same thing.

Paul

Thanks for the link. I watched it right through and learned a lot.

In message snipped-for-privacy@4ax.com, at 18:15:09 on Tue, 6 Jan 2026, Scott snipped-for-privacy@gefion.myzen.co.uk> remarked:

400v not so much.

FWIW 'FADEC' and 'fly by wire' are different things. The pilots had time on the 737 (presumably 737-300 at that point) and A310, which have FADEC, ie there was a 'ECU' between the controls and the engines (instead of a flight engineer who was previously a human ECU). By 1989 I think FADEC was common, and crew would have been trained on emergency situations on it in the simulator.

But the A320 was the first airliner with fly by wire, meaning in addition to FADEC there was also an ECU between the control input (sidestick) and the control surfaces. Older FADEC aircraft like the A310 had a yoke with mechanical pulleys connecting to the rudder, elevator, ailerons, etc (with hydraulic assist, like a car with power steering).

Those two computers would communicate, allowing the flight control ECU to tell the engine ECU what to do in certain circumstances. That's something that was new in the A320 family.

Theo

Good, thanks - this explains it.

ROFL. Thats because it is just a standard golf floorpan and drivetrain with a different body.

We were talking EVs! VW ID.3, ID.4, ID.5, ID.6 and ID.Buzz are all rear drive.

nib

I think it is more to do with the weight distribution. Many years ago I was commuting in a Hillman Imp, and that had the engine in the back driving the rear wheels. One snowy morning I set off to work and the steering felt rather light though still usable and the rear wheels dug right through the snow and it just went. Where I was working at that time was at the top of a 1 in 9 hill, and I was one of only 11 cars that got there that morning.

I imagine the VW Beetle would have been similarly OK in snow, but I have never driven one of those.