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[protomech]

I coasted down a .. probably 15% grade today @ 25 mph, regen was useful for holding my speed down the grade. Suspect it has little real effect, but need some better instrumentation to verify.

Even riding the same route twice under the same conditions, the regen effect will probably be lost in the instrumentation margin of error. Maybe you could use distance to the disappearance of a certain bar, although I don't know how repeatable that is.

[flar]

flar mentioned a whining sound. Any owners hear that?

That could probably have been just as easily explained by really hard pads on a drilled rotor come to think of it, so don't read too much into that comment...

[flar]

I just found this on the Zero S "features" page:

• Quad-level regenerative system recharges the power pack when decelerating
• Re-gen level is increased during brake application vs. “neutral” deceleration
• Both braking and “neutral” re-gen levels are set higher in Eco vs. Sport mode

It would be nice to see a breakdown of when the "quad" levels come into play.  Does that mean that there is regen while coasting on Sport?  Does braking induce more than one additional level of regen?  I could see the easiest breakdown would be based on the 2 switches (eco/sport vs. brake light) simply being 2 binary bits that choose a level with the throttle switch being an enable switch:

T = throttle switch on
E = echo switch on
B = brake light switch on

T- E* B* = no regen
T+ E- B- = regen level 1
T+ E+ B- = level 2
T+ E- B+ = level 3
T+ E+ B+ = level 4

Or maybe the middle two could be the other way around?

[protomech]

There's at least two levels of regen braking before you hit the actual brakes IIRC. Sport does regen while throttle is in the neutral position, but the amount of regen is no more than half that in Eco mode.

It's difficult to distinguish regen braking from normal braking.

[dkw12002]

What would convince me regeneration was working was if a bar CAME BACK as I was braking going down a hill. My battery displays regenerative stopping. If I have 4 bars, stop and turn off the bike, then in 20 min. start up again, I have 6 bars. I'm convinced this is no quirk either cause the 2 bars I gained do not suddenly disappear. Something has happened in the chemistry that has produced some more energy from the batteries, I think. By the way, this happens with my e-bikes and even an electric weed wacker but to a much less degree. After a rest, you gain some energy. If I ever thought I was going to run out of battery and had 10 miles to go, I would stop the bike, wait a while, then continue. I think this might give you some extra electricity to limp home although I don't know if it would be good for the battery.
 

[Richard230]

Speaking of regen, yesterday I had my bike fully charged when Ieft my home. I live at the top of a 1/4 mile long hill and keep the throttle closed all the way down. I had my bike on Eco mode and noticed that the regen drag jerked off and on down the hill. It did the same thing while coming to a stop at an intersection a short distance further. But on my way back home, after draining the battery pack of a couple of bars, as I was riding down another steep hill, I did not notice the jerking any more.  My guess is that the fully charged battery pack was not happy accepting the current created by the strong Eco mode regen until the pack had discharged somewhat. It appeared that the controller was cutting it on and off until pack had been partially discharged.

I might add that I do not notice the same jerking, under the same circumstances, when in Sport mode.

Having owned an electric motorcycle without regen, I can tell you that the Sport mode does generate drag (and I assume power at the same time) when the throttle is closed. My first non-regen GPR-S would really coast with the throttle closed and felt very much like a two-stroke with the throttle off - or a standard motorcycle coasting with the clutch pulled in. There is definitely more drag, even in Sport mode, compared with coasting in "neutral".

Finally, I can tell you that regen provides very little power replacement during your ride, compared with not having it.  My second GPR-S had regen set at 100% and the most I ever saw was a 3% power generation over a long ride with lots of hills. Most of the time the power generated was less than 2%. So don't expect regen to extend your range by much. Mostly what it does is to cut down on your brake pad wear and make the bike feel more like a 4-stroke IC motorcycle. 

Keep in mind that the vast majority of your ride is with your throttle open and not closed. Even when the regen is activated, the amount of power produced is much less than the amount of power consumed by the motor. Regen helps some, but not much.

[Lipo423]

The BMS is definitely "managing" the situation here, and avoiding potential over-charging your battery.
As I have said in a different post I own 2 Tidalforces (Electric bicycles) these bikes were made in 2002-2004 and they did have regenerating braking, cruise control, and probably the quietest electric motor I have ever seen in my life.
Regerating braking is more a "marketing thing" or braking thing than a real advantage, you normally get around 10% back to the battery, no more. When designing the system you have to be carefull as the current raises suddenly, and drops the same way...it is very difficult to manage such changes without putting the battery at risk, so you end up with little current back to the battery.
I only remember once when I was riding this bike (it had two regenerating settings, one when riding over the max. set speed and another one -harder- when braking)recovering 20% of energy in a +20% grade 7 Km downhill.

[protomech]

My bike doesn't regen at all in Eco mode when it's pulled hot off the charger. It takes maybe a half mile before I start to notice regen effects. The same thing applies to the Nissan Leaf btw - part of why the Nissan Leaf has two piston front brakes that in normal use are barely used.

An electric motorcycle (540 lbs with rider) with a 8 kWh pack can tolerate a much higher regen current than a e-assist pedal bike (300 lbs with rider) with maybe a 200-500 Wh pack.

Compare an EV car vs EV bike, vehicles start from rest, accelerate to 40 mph, then regen brake (50% KE back into pack).
1. Nissan Leaf uses 300 Wh for the mile. KE = 256 kJ or 71 Wh. Say 35 Wh back into the pack or 12% regen.
2. Zero S ZF9 uses 100 Wh for the mile. KE = 39 kJ or 11 Wh. Say 5.5 Wh back or 5.5% regen.

The controller, motor or battery may be a further limiting factor. The EIG cells I think Zero is using have a maximum recommended 0.5C charge rate .. though they may be able to accept a higher charge pulse from regen braking.

Without a tool like a cycle analyst I think it's hard to say how much you actually are getting back. I suspect it's on the order of 3-5% at best.

[dkw12002]

Even then, if the slowing down results in a slight charge, this may not equate to more distance because had you not slowed down, the bike would have gone faster and used less energy getting up to speed at the bottom of the hill.  It is only if there is a stop sign at the bottom of a steep hill, or with stop and go traffic that you would actually gain anything from regenerative braking.

Speaking of e-bikes. I get really great range with mine because I seldom stop at stop signs and I cut across parking lots making the distance and stopping time shorter than if I were riding a motorcycle or car. While riding an e-bike in this manner is not legal, I have never yet seen anyone stopped on a bicycle for anything. They ride on the sidewalk, don't stop at stop signs, do U-turns, cut across parking lots, etc.  Even if you did get stopped, you would not lose points on your license because you don't need a license for an e-bike. The police could still fine you and confiscate your bike of course, but this is very unlikely. The fact bicycles are ridden by children and still thought of as a toy works to your advantage in this regard.  Something to think about if you do a lot of in-town riding only.

[flar]

The EIG cells I think Zero is using have a maximum recommended 0.5C charge rate .. though they may be able to accept a higher charge pulse from regen braking.

With 3 accessory quick chargers you end up charging the ZF6 pack in 1.8 hours.  Given the non-linear nature of the charging, it is probably a bit higher than 0.5C for that first hour, no?

[protomech]

My onboard charger typically charges between 850-950W and appears to be ~93% efficient, so probably delivers 800-850W to the pack.

Three additional accessory chargers would bump the charge rate to 3.2-3.4 kW.

For a 5.3 kWh battery that's a 0.64C charge rate (0.43C for the 7.9 kWh battery).

I would suppose Zero has either qualified the battery pack for those charge rates beyond EIG's specifications, has a slightly tweaked chemistry for higher charge, or limits the chargers when 4 are connected.

@dkw, you're correct that you're most efficient by slowing via coasting instead of regen. In a world of stop lights and traffic you don't always have the option to coast to a stop. The gate I go through each day is on a 55 mph restricted-access road and has posted 35 mph and 25 mph speed limit signs approximately 0.25 miles before the gate. In practice traffic moves at 60-65 mph and in morning traffic people will ride on your ass at that speed until the 25 mph speed limit sign.

If traffic permits, my Honda Insight can slow from 55 mph through regen only by starting approximately 0.35 miles out from the gate. It has a maximum regen of 50A (144v system voltage), or about 7 kW slowing ~2000 lbs. Probably around 7C into the ~6 Ah pack.

The Zero can slow from 55 when I hit the 25 mph sign (maybe 0.15 miles from the gate?) .. maybe 4 kW + drag slowing 540 lbs.

[Richard230]

I might have mentioned this before, but my sepex GPR-S was programmed from EMS with 100% regen and came with a Cycle Analyst display. I once got the bike up to 70 mph (that big motor was not happy about that) downhill, touched the brakes to activate the regen and the CA showed that the motor was producing 60 amps (at 80 volts) into my 50 Ah battery pack. But that generation only lasted a few seconds until the drag slowed the bike down to 50 mph (30 amps) and then 10 amps at about 30 mph. The problem is that this power is only generated when you are slowing down and you just don't do that for very long, compared with the length of your typical trip.