Technical Mechanical Questions - Converting to Electric

"Quantumstate" wrote

I'd look around for another website focused on electric conversions and ask the question there.

My parking brake holds my 330xi perfectly adequately on any hill in Seattle. You won't do any better than that.

Even on your "electronically controlled" Jeep, it probably needs hydraulic power to operate. Every recent OD on an automatic transmission I know about is a planetary gearset integral with the transmission that is operated by hydraulics. Older ones (on '50s Chrysler products for instance) on manual transmissions were operated by electrical solenoids (as might be your Jeep).

An electric motor DOES NOT need an overdrive.

FloydR

ask the question there.

Well, of course I have. But there is simply not the raw mechanical depth I was hoping to find, so am turning to racing forums.

Most electric conversions are quite primitive. Essentially, I am trying to make one like a regular car.

AC electric motors do not, true, although DC motors need a tranny and OD would be nice. For any amount of freeway driving though, overdrive would save quite a bit of power. I am the first to think of this, but I do know OD would be quite desirable, if technically possible. Only question is, exactly how do they work?

Interesting project. I would disagree with your statement that you don't need a transmission. You can't really expect to run 15000 rpm through the stock driveshaft designed for less than half that value. So you either need to mount the electric motor closer to the new high ratio rear end or you need a fixed 2:1 to 3:1 reduction up front to keep the driveshaft speed in the range it was designed for. I guess you could leave the transmission in the car and just use 2nd gear all the time. It would be interesting to see how long it lasted. As far as a fixed ratio gearbox, the one in the Prius might just fit the bill and should be available in your local junk yard.

Max speed of the motor is 9,000rpm, but it is a good point. Anyone knoe what the normal second-gear ratio for a 325 is?

Where are you going to get AC power? Jim

Wouldn't he just need a really, really long extension cord?

I wish him luck. If this was easy, we'd all be able to buy one from BMW.

Probably a *big* inverter drive. These are dmaned expensive too, and need much cooling. I'm still curious as to where he's going to put the (many) batteries. I guess the original vehicle's 50/50 weight split will go to hell.

JB

Won't matter for a city only car - and that's all an all electric one will be.

Jim, AC power comes from an inverter, which converts battery DC to 3-phase AC for the Siemens motor. My conversion will be along these lines:

Tom, it's not that it's difficult. I am just trying to bridge that last gap to making it like a regular car. No, this is well within BMW's realm. Ever heard of the Solectria car? The electric S10 pickup? The GM EV1? All dead now, thanks to Big Oil's big money buying them off. See the movie, "Who Killed the Electric Car".

JB, battery technology has come a long way since you last checked. Lithium ions are a fraction of the volume and weight of lead-acid, and pack many times the energy. Check these:

which are what was used in the Eliica supercar: And check out this little monster: Here I thought we Americans were the only ones 10 years behind the times. Dave, electric vehicles don't have to be city-only. How's about a trailer, with an ICE engine, which actually PUSHES the electric car on long trips: or an Insight engine/generator trailer, which provides 10kW while theEV motor draws 7.2?

That should put the doubters to rest. Now, are there any automotive engineers in the house, who can help with my questions?

Are there any automotive technicians in the house?

You should maybe find out a bit more about the car you've got. The parking *brake* applies shoes to the rear brakes via a cable. Not really any good for handbrake turns but it should keep it on a hill. Speedos are electronically driven. Used to be from a sensor on the final drive and probably still is.

Since this is a BMW group and BMW don't make electric cars why would you expect to find a suitable one here? I'd guess there are far more suitable groups around since your questions are not really marque specific.

I don't have the car yet. We are considering this as the target car for a series of conversions.

I did expect that the parking brake is cable, but I also know that in the majority of modern cars the parking brake is inadequate on hills. It's a safety issue.

Sure, the speedo is going to be electronic, sure. Likely a gear-driven cable to a hall-effect sensor near the ECU. Well, I need to find another place to take off the gear, as we are trying to eliminate the tranny.

Dave, why are you asking me to defend myself, for asking mechanical questions about BMWs in the BMW forums? The purpose of a forum is to exchange information, and I am hoping to find some open-minded creative people here. That's all.

I would agree that if they are considering doing this mod on a BMW that they are in the right place.

There is no cable from the differential to the sensor. The sensor is mounted directly on the differential and reads the rotation of the ring gear.

I seem to recall (perhaps incorrectly) that the E46 speedometer is driven from one of the wheel ABS sensors.

JRE

We? You're not seriously suggesting this as a commercial venture?

Near every BMW is available with a manual transmission, and those which are have an identical handbrake to the autos.

Cable drive speedo. Gawd help us.

I'd try and find a milk float group. Do a Google if you don't know what I mean. Their technology will be right up your street.

Thanks Jack and JRE for your help with the speedo. Seems that will not be an issue with this model.

I'm wondering about my other questions now.

Maybe someone is willing to make some productive comments, unlike Dave, in his vain pride polluting this thread.