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.WRONG----Reduction gear losses are only a few percent. Synchronous motors (like the LEAF uses) are mid 90's percent efficient when either delivering power to the gears or generating power. Since there are small losses, the regeneration from going downhill will not quite match the energy to go up the hill. The difference is not large if the speed is kept the same going both ways.alozzy wrote: ↑Sat Sep 24, 2022 12:00 am Any amount of regen results in considerable losses...
An EV's motor is at best 80% efficient at converting electrical energy to mechanical output at the drive shaft. Then, there are some losses in the gear box too.
When regen kicks in, the EV motor becomes a generator, converting mechanical energy at the drive shaft back to electrical energy stored in the pack. However, most EV motors aren't as efficient at acting as a generator vs a motor.
In a perfect system, regen recovered energy would be the power originally drawn from the pack times the square of the motor's efficiency.
So, assuming perfectly symmetrical efficiency (unlikely), if 10 kWh of energy is drawn from the pack to accelerate a vehicle from 0 to 30 mph, then regen would at best put back 10 * 0.64 = 6.4 kWh back into the pack when decelerating from 30 mph to 0 mph.
But, EV motor's efficiency isn't linear at all speed either. Then there are the gearbox losses to consider...
I would guess that if you can get 50% regen efficiency average (so 70% motor and gearbox efficiency combined), that's pretty good.
I've had conversations with people who swear that they can go up a hill and come back down again and end their trip with "almost the same pack SOC". It's laughable that they think that's even close to possible.
Note that with cruise control, the car will do regen on downhill sections or when slowing down with adaptive cruise. If you want higher efficiency, you need to learn to coast in neutral at the right times. Doing that can definitely beat cruise control on longer trips, unless the highway is dead flat and you never change speed. Coasting downhill is super efficient, unless you go so fast that increased air drag cancels any gains.
I think you're drinking the Nissan kool-aid with respect to efficiency - peak efficiency maybe, but I am skeptical that average efficiency is as high as you state.(EV) losses can be broken down into approximately 10 percent of the source energy from the grid lost in the charging process, 18 percent lost to the drivetrain motor components, up to 4 percent lost to auxiliary components, and another 3 percent lost solely from powertrain cooling and other vehicle systems.
I was under the impression that the E-pedal only used friction brakes at the very end of braking, once you've reached a very low speed, in order to bring the car to a complete stop and then keep it from creeping.
E-pedal doesn't actually use full regen until your speed is under some threshold. Try it out on the Interstate doing 70 mph and just let go of the accelerator and watch LeafSpy, it limits regen to the same amount as B mode until your speed is low enough to engage a higher regen (and then your brake lights come on too). I'm not sure of the speed, maybe under 50 mph you get full regen? I think it was that way on purpose because full regen at Interstate speeds just mean someone will crash into the back of you every-time.GAXIX wrote: ↑Thu Oct 27, 2022 10:17 amI was under the impression that the E-pedal only used friction brakes at the very end of braking, once you've reached a very low speed, in order to bring the car to a complete stop and then keep it from creeping.
At what other times does the e-pedal use friction brakes? During max regen?
It took me a while to get the hang of using neutral, but wow, you're right. This coasting in neutral can make for some very impressive efficiency gains. I managed a max of 7 mi/kWh on my normal 19 mile one-way trip (slightly downhill direction, maxxed 5 mi/kWh on the uphill direction), never got that good before.
