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Discussion Starter · #1 ·
Not your usual EV question + some ignorance on my part. I'm currently (no pun intended) wiring a 96V / AC50 / Curtis1238e in a home-built hybrid sports car with ICE rear drive, and EV front drive for added torque under acceleration. My goal is to have the two throttles physically linked (cable on ICE to PB8 on EV) and configured to have the EV power "on" at higher throttle (accelerating), regen "on" at lower throttle (cruising). I'm an EV newbie and the use of an electric motor is an experiment, so I could use some guidance / suggestions about the regen idea. Any thoughts?
 

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This appears to me to be what Chevrolet is doing, in principle, with the upcoming C8 Corvette hybrid.

That said, it seems a bit dangerous to have a passively modulated electric throttle via mechanical linkage, though you could bias it, perhaps, for controllability during bad traction conditions. It'll need testing and tuning.

Many EV's are front wheel drive, so having the front wheels only do regen is not unconventional.
 

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Discussion Starter · #3 ·
Thanks for the comment. The EV system will be switched. Also, I could eventually use a throttle position sensor and other data from the ICE system for a more sophisticated setup. For now, a simple question - how will regen behave in this scenario? A techie at the motor supplier suggested that regen is "on" when the throttle is reduced and not requesting higher speed from the motor, but I'm not sure I understand what he meant.
 

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That's part of the tuning I talked about.

The EV system will need to be dominant when not charging, so regen will come on when you let off on the throttle, and the ICE will need to be dominant if you want to charge the battery by regen, meaning the electric motor is always in regen.

Switching it off may not be a good idea as kicking it on and off while rolling might fry the controller with the voltage the motor can produce by merely turning.
 

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Yeah, agreed that you would not want to literally turn the controller on and off as it needs precharge time and such to turn back on, but with some custom code (not easy to get access to with Curtis/HPEVS) it could have some inputs mapped to disable all drive and regen under certain conditions.
In a recent post cricketo was discussing the deadband settings in Curtis throttle menu, which means you could have the EV system not demand drive torque until higher level of throttle pedal input. There is also a brake pot input which, in combination with "neutral braking" settings could mean you could set up the controller to have no neutral braking regen and only activate it during brake pedal input. Having regen on at cruising as you mentioned is not the way I would go as it is less efficient than drive current with these setups and causes more heat in the motor/controller also, meaning a fairly inefficient vehicle. Rely on the regen to charge the pack only at braking would be the cleanest setup IMO.
 

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That would be true for an economising hybrid, but in a performance booster you'll suck out a lot more than regen ever could put back in. The PHEV C8 claims almost no fuel economy gains, just performance boost.

So, you are taking excess power from the ICE (through the road) and storing that for performance boosted acceleration or bringing a loaded truck up to speed.
 

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This is a well-established design - engine-only for rear wheels, electric-only for front wheels - but it generally doesn't work very well, so it is not common. The best-known example would be the BMW i8.

Some vehicles such as the Acura NSX look like this, but are significantly different because they also have a motor-generator for the rear axle.

My goal is to have the two throttles physically linked (cable on ICE to PB8 on EV) and configured to have the EV power "on" at higher throttle (accelerating), regen "on" at lower throttle (cruising).
For now, a simple question - how will regen behave in this scenario? A techie at the motor supplier suggested that regen is "on" when the throttle is reduced and not requesting higher speed from the motor, but I'm not sure I understand what he meant.
That's not how EV accelerator ("throttle") controls are typically used. They don't set a speed target; instead, they are interpreted as a torque or power request. If all you connect to the electric motor controller is a pedal signal and some sort of regen request based on pedal position, you're setting up a system that uses power to drive the motor at high accelerator pedal positions and generates at low positions... all the time. While you drive slowly the engine will be working to drive against the motor which is acting as a generator.

One reason that hybrids are rarely done as DIY projects is that the control system required to make it work well is too complex and difficult.
 

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Discussion Starter · #9 ·
Thanks for all the feedback and thoughts. I think I may have a workable solution to test "cruising speed regen".
(1) Link the ICE and EV throttles to open simultaneously.
(2) Set the EV controller for low percentage neutral braking regen,
(3) Adjust the wiper voltage at the throttle deadband threshold high enough to start demanding EV torque when the ICE throttle is opened more than for normal acceleration or maintaining cruising speed.
(4) Use throttle mapping as needed to manage the EV torque curve.

Conditions for success include (1) the ICE has adequate "surplus" energy (hp) at cruising speed to not be power compromised, (2) the controller prevents overcharging, and (3) the motor or controller don't get too hot.

Simple backup plan would use a momentary switch to turn on low percentage braking regen manually while cruising along.
Cheers!
 
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