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Old 07-08-2016, 01:05 PM   #1 (permalink)
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Dual complete Leaf drivetrains in parallel?

Hello all,

So I've been asking about high voltage systems and paralleling OEM EV motors on a single controller, but I've got a different idea now that sounds - to an ME at least - easier to accomplish, and uses almost all OEM parts as well, to get the same goal: more power.

I'd like to figure out how to run two Nissan Leaf motor/inverter systems in parallel, as well as 2 or more battery packs, possibly also chargers, AC systems, etc. depending on how large the vehicle I put them is. 160kW/560N.m. (215hp/420 ft-lb) should be plenty, similar to a stock early 90’s Ford 351W truck engine. (I am currently considering a 1992-1993 Ford Bronco due to having an NHTSA 4*/5* frontal crash rating without any airbags. 1994 added a driver airbag for a 5*/5* rating, but we’re talking about a 23 year old truck, and wiring harnesses corrode, new airbags are ~$1500, new sensors are ~$250 if available, etc.)

There's a few folks out there who are adapting complete Leaf drivetrains into alternate vehicles and figuring out how many of the OEM bits are needed to keep the system happy enough to still run, so that’s pretty straightforward. The not-yet-figured-out bits are how to integrate the Leaf brake controller into the vehicle’s braking system, so as to get the feedback needed for regen braking. Current theory is that no regen other than throttle-off will be available without the brake controller interfaced. That ought to be figured out before I get a budget, so not worried about that yet.

So, what all is involved in slaving duplicate devices together on a single CANbus? I think EVTV is working on hacking the CANbus commands so they can run the motor/inverter (and other parts like chargers, AC, etc.) standalone with their GEVCU device. That might be the path forward, but if there’s an easier way to “clone” signals or “spoof” the CANbus so that added devices are slaved to the original devices, that would (maybe?) allow using all stock Nissan parts and code.

I can also see the same techniques used to make an AWD dual-motor Leaf, by grafting a second front subframe in place of the rear suspension to hold the second complete drivetrain. The harder part would be figuring out where to put a second battery pack (to handle the current draw – stock pack is rated 90kW and that’s not enough for two 80kW motor/inverters) and how to deal with the extra weight of it – might need to turn the car into a 2-seater.

Thoughts?

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Old 07-11-2016, 07:23 PM   #2 (permalink)
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Quote:
Originally Posted by cajunfj40 View Post
There's a few folks out there who are adapting complete Leaf drivetrains into alternate vehicles and figuring out how many of the OEM bits are needed to keep the system happy enough to still run, so that’s pretty straightforward. The not-yet-figured-out bits are how to integrate the Leaf brake controller into the vehicle’s braking system, so as to get the feedback needed for regen braking. Current theory is that no regen other than throttle-off will be available without the brake controller interfaced. That ought to be figured out before I get a budget, so not worried about that yet.

So, what all is involved in slaving duplicate devices together on a single CANbus? I think EVTV is working on hacking the CANbus commands so they can run the motor/inverter (and other parts like chargers, AC, etc.) standalone with their GEVCU device. That might be the path forward, but if there’s an easier way to “clone” signals or “spoof” the CANbus so that added devices are slaved to the original devices, that would (maybe?) allow using all stock Nissan parts and code.
So - running 2 Leaf controller/motor/drivetrains, and ABS feedback/regen braking ... with one or two battery packs and chargers, inside one vehicle with one throttle? And keep all OEM parts.

A single throttle into the GEVCU, and the GEVCU sending that signal to the same inverter address on two different CANBUs channels .. sounds like it might work. The brake pedal would need to work the same way, and both controllers can keep their own motor encoders, wheel encoders (or whatever they use to determine wheel speed) and deal with their own braking.

The brake light signaling could be an OR of the signals from each controller.

Quote:
I can also see the same techniques used to make an AWD dual-motor Leaf, by grafting a second front subframe in place of the rear suspension to hold the second complete drivetrain. The harder part would be figuring out where to put a second battery pack (to handle the current draw – stock pack is rated 90kW and that’s not enough for two 80kW motor/inverters) and how to deal with the extra weight of it – might need to turn the car into a 2-seater.
Leaving the entire drivetrain stock .. * 2 .. and keeping them split except for the GEVCU and a couple of relays for the brake lights ... I can' find any holes in that at the moment.

The GEVCU code may need some tuning to put more braking on the 'front drivetrain' so that the rear end does not swing out during hard braking ... perhaps a fairly minor set of code?
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Old 07-13-2016, 08:21 AM   #3 (permalink)
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When you mentioned grafting subframes, that got me thinking about grafting the complete subframe into the frame of your intended Bronco. I assume that the track width of the Leaf is as much as a foot narrower than that of the Bronco, so that will probably be a non-starter.

Taking out all of the conventional drivetrain underneath leaves lots of room beneath the Bronco for installing custom mounts for the batteries there. Just how tall is a Leaf pack, anyway? According to one source it's just under 11" high, by about 4 by 5 feet. You might have difficulty fitting two down there. I guess break the other one up and salt it around the vehicle, mostly under the hood.
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Old 07-14-2016, 04:54 PM   #4 (permalink)
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Quote:
Originally posted by thingstodo: So - running 2 Leaf controller/motor/drivetrains, and ABS feedback/regen braking ... with one or two battery packs and chargers, inside one vehicle with one throttle? And keep all OEM parts.
That about sums it up, yes.

Quote:
A single throttle into the GEVCU, and the GEVCU sending that signal to the same inverter address on two different CANBUs channels .. sounds like it might work. The brake pedal would need to work the same way, and both controllers can keep their own motor encoders, wheel encoders (or whatever they use to determine wheel speed) and deal with their own braking.

The brake light signaling could be an OR of the signals from each controller.
I would use just one set of wheel encoders and duplicate the outputs - this isn't likely to be a "one transaxle per end" conversion.

Quote:
Leaving the entire drivetrain stock .. * 2 .. and keeping them split except for the GEVCU and a couple of relays for the brake lights ... I can' find any holes in that at the moment.
Sounds good to me!

Quote:
The GEVCU code may need some tuning to put more braking on the 'front drivetrain' so that the rear end does not swing out during hard braking ... perhaps a fairly minor set of code?
I wouldn't know on the coding. Sounds like a "digital brake bias" controller. Not really something I want to fiddle with, though.

Quote:
Originally posted by elhigh: When you mentioned grafting subframes, that got me thinking about grafting the complete subframe into the frame of your intended Bronco. I assume that the track width of the Leaf is as much as a foot narrower than that of the Bronco, so that will probably be a non-starter.
Not what I intended - I'll twin the motors into a single gearbox and run through a transfercase. A Nissan Leaf has 24.9" tall tires ~810 revs/mile, and is governed to 95mph. I intend to run 33" or 35" tires ~611 to 576 revs/mile eventually. One OEM motor/gearbox at each end (IRS conversion in the rear needed, custom half-shafts all around, too) would have me geared at 126 to 134mph top speed. Way too fast! Dual stock drivelines 1 each fore/aft is for stock height or lower tires only. A Fiat 500 has 23" tall tires ~877 revs/mile. Packaging would be interesting, but it would absolutely rip to 88mph.

Quote:
Taking out all of the conventional drivetrain underneath leaves lots of room beneath the Bronco for installing custom mounts for the batteries there. Just how tall is a Leaf pack, anyway? According to one source it's just under 11" high, by about 4 by 5 feet. You might have difficulty fitting two down there. I guess break the other one up and salt it around the vehicle, mostly under the hood.
I'd be repackaging the batteries - it is the OEM wiring hookup that is important for functionality. I'd make a box or boxes similar in concept to the OEM ones in terms of how well sealed and their degree of protection as needed to contain them where I think they'll fit best. Gas tank location, between the framerails in the rear, under the hood, etc. Generally as low as possible but still above the bottom of the framerail so they can hide behind a skidplate.

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