[electroniceric]

Hi all,
I've gotten increasingly interested in EVs and have rented Tesla's a couple times. I just bought a Pacifica plug-in hybrid and I have to say I'm pretty thrilled with it. We drive on electric about 90% of the time, but my wife doesn't have range anxiety and she's getting more turned on to EVs.

I'm now looking at getting a convertible 1987 BMW i325 - a car my wife used to own and still loves- as a present to her for a fun car, and wanted to see if I can could get some advice on converting it to plug-in hybrid. Full disclosure: I'll probably try to hire someone to do the actual install once I have a handle on what is feasible for this car - I'm pretty handy with software, data, and light carpentry but have never put a wrench to a car.

I'd love to achieve about 25-30 mi of range on electric. From what I've read here, the setup is likely to involve a rear axle electric motor (the car is RWD) and battery either under the seat or occupying part of the trunk. So in theory there is no change to existing gas motor or transmission.

What I'm confused about (or maybe I'm being unrealistic) is how to incorporate the electric motor into the existing transmission. My Pacifica has a complex dual motor setup where both electric and gas motors can fire together - truthfully it's a pretty impressive piece of engineering. For this conversion I'm imagining something much simpler. Honestly my starting point is a switch on the dash that changes the car from electric to gas. I can imagine some concerning aspects of this (e.g. what if you run out of battery at 65 MPH and need to switch in a hurry). Can the accelerator be set up to run these two systems independently?

Ideally it would be possible to add regen braking, but I suspect this may add cost/complexity .

Does anyone have thoughts or experiences to share? Would love to hear if anyone has been successful with this battery hybrid type approach.

Thanks!

Eric

 

[Electric Land Cruiser]

Nobody has successfully made a diy hybrid on this site that I know of in at least a decade or more of trying. My advice would be to make it fully electric as it will be easier. You can probably get it close to 100 miles electric range with the right setup. An EV conversion costs about $20k and up just for labor right now FYI.

 

[brian_]

From what I've read here, the setup is likely to involve a rear axle electric motor (the car is RWD) and battery either under the seat or occupying part of the trunk. So in theory there is no change to existing gas motor or transmission.

While it's theoretically possible, I've never heard of a vehicle in production with a final drive unit incorporating a shaft input (from the transmission) and one or more electric motors. Parallel hybrids for this configuration of vehicle place the motor-generator either between the engine and transmission, or between the transmission and the final drive unit (rear axle).

What I'm confused about (or maybe I'm being unrealistic) is how to incorporate the electric motor into the existing transmission. My Pacifica has a complex dual motor setup where both electric and gas motors can fire together - truthfully it's a pretty impressive piece of engineering. For this conversion I'm imagining something much simpler.

Only a pure series hybrid design would be mechanically simpler than the Pacifica Hybrid's power-split transmission... but of course you're ignoring the complexity of the existing BMW transmission because it is already there. The Pacifica Hybrid uses the same design as a Prius or similar Toyota models.

The best conversion would be to swap the existing transmission for the parallel hybrid transmission of a recent BMW hybrid... or just to sell the car and buy the hybrid instead. BMW uses hybrid versions of the ZF 8HP transmission.

Ideally it would be possible to add regen braking, but I suspect this may add cost/complexity .

Any system using a reasonable motor (not a series-wound brushed DC motor) can regeneratively brake; the challenge is coordinating that with the regular brakes... but coordinating the electric and other components is the big challenge in any hybrid, in every aspect.

 

[salesabbastrucks]

Hi all,
I've gotten increasingly interested in EVs and have rented Tesla's a couple times. I just bought a Pacifica plug-in hybrid and I have to say I'm pretty thrilled with it. We drive on electric about 90% of the time, but my wife doesn't have range anxiety and she's getting more turned on to EVs.

I'm now looking at getting a convertible 1987 BMW i325 - a car my wife used to own and still loves- as a present to her for a fun car, and wanted to see if I can could get some advice on converting it to plug-in hybrid. Full disclosure: I'll probably try to hire someone to do the actual install once I have a handle on what is feasible for this car - I'm pretty handy with software, data, and light carpentry but have never put a wrench to a car.

I'd love to achieve about 25-30 mi of range on electric. From what I've read here, the setup is likely to involve a rear axle electric motor (the car is RWD) and battery either under the seat or occupying part of the trunk. So in theory there is no change to existing gas motor or transmission.

What I'm confused about (or maybe I'm being unrealistic) is how to incorporate the electric motor into the existing transmission. My Pacifica has a complex dual motor setup where both electric and gas motors can fire together - truthfully it's a pretty impressive piece of engineering. For this conversion I'm imagining something much simpler. Honestly my starting point is a switch on the dash that changes the car from electric to gas. I can imagine some concerning aspects of this (e.g. what if you run out of battery at 65 MPH and need to switch in a hurry). Can the accelerator be set up to run these two systems independently?

Ideally it would be possible to add regen braking, but I suspect this may add cost/complexity .

Does anyone have thoughts or experiences to share? Would love to hear if anyone has been successful with this battery hybrid type approach.

Thanks!

Eric

Hi
The Mercedes S400 hybrid has an electric motor between the engine and the gearbox. I am not sure how it has been incorporated with the torque converter but the vehicle works smoothly with both the gasoline motor and the electric motor through a 7 speed automatic gearbox

 

[remy_martian]

Yes, it does. It has thousands of lines of software and dozens of engineers that make the magic happen...with that motor, with that engine, with that vehicle. A hybrid is way beyond the abilities of 95% of the people here and the other 4.999% are informed enough about the effort & scope to not waste their time doing it.

Nothing stops anybody from doing a full transplant from a donor car. But everything has to be transplanted, all harnesses, control modules, sensors, and driveline components and charging system and storage systems.

You keep seeking an answer you won't find. There is no "bolt a motor between the engine and trans" that will work nicely on the road as a hybrid vehicle does. If you want a hybrid, buy one.

 

[brian_]

The Mercedes S400 hybrid has an electric motor between the engine and the gearbox. I am not sure how it has been incorporated with the torque converter but the vehicle works smoothly with both the gasoline motor and the electric motor through a 7 speed automatic gearbox

Parallel hybrids which mount the motor between the engine and transmission typically omit the torque converter, using an enhanced first gear clutch to handle the slipping required to get moving from a standstill and assisting those starts with the motor; that's how BMW hybrids using ZF transmissions work. The Mercedes S400 only has a little 15 kW motor, like an early Honda Insight, or the "mildest" variants from ZF. It appears in this illustration from Mercedes that in this case the torque converter is retained, and the motor is mounted ahead of it, although what's connected to what and how is not clear.
Mercedes-Benz S 400 HYBRID: The CO2 champion in the luxury class, with an efficient hybrid drive system and lithium-ion technology

Duplicating this configuration - whether the ZF/BMW version or the Mercedes version - to anything close to the level of sophistication of the OEM version would be very difficult. Building something functionally similar would be practical, but still not easy... and much more difficult than just buying as a complete car.