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[Tater McTatums]

I've had my 2014 SR for just over two weeks now and I've had a curious issue with the regenerative braking on a few occasions. Typically I ride in Custom with all of the settings maxed with the exception of "engine braking" regen, which I have set to 0%. I've noticed that with a full charge the regen during braking will pulse on and off until the charge remaining drops to 99% or below. Any point 99% or below and everything works like normal. I've just been starting off in Sport until I use a bit of charge and its been a non-issue. I'm assuming that this is normal behavior but if it's not please let me know.

The malfunction I'm specifically referring to has occurred twice now, both when starting off with a full charge. During both occasions it was nighttime (slightly colder temps, approx. 45°F or above) and both times I had no regenerative braking whatsoever.  I tried changing modes, mainly because I know Eco has both engine braking regen and braking regen. Even in Eco there was no regen at all. The meter on the right hand side of the display confirmed that the bike was not performing any regen while this was occuring. The first time I rode until I got to a friend's house (about 6 miles) at which point it showed 94% remaining. I shut off the bike for a few minutes while I read through the manual and searched this forum, hoping to find someone else who had had this occur. My search turned up empty. I decided to just ride the bike and call Zero in the morning if it persisted. Upon turning the bike back on it showed 98% remaining (the bike was not plugged in while I was searching). When I rode away the regen was working like it always has so I chalked it up to a one time glitch. A few nights later I had it happen again, once again with a full charge. This time I just turned the bike off for about 30 seconds and when I turned it back on it was working fine. And during both times there was no warning light and nothing else seemed affected.

Is this a somewhat common occurrence or indicative of something more sinister? Granted I've only had it happen to me twice in ~900 miles. And since a quick reboot seems to solve the problem it's not a huge issue, albeit annoying. I'm mainly just curious if anyone with some more time with their bike has run into this.

[kensiko]

You need to have energy storage available to take out this energy. If the battery is full, no place to store it. So it's normal.

[Doug S]

As far as the pulsing at very high (99%+) battery SoC, that's normal...it doesn't want to overcharge the batteries, and they apparently didn't put any hysteresis on the threshold, so it pulses back an forth deciding whether it can or cannot charge the batteries any more. My bike does it every day, since the first 1/2 mile or so from my front door is downhill. Annoying but not serious.

As far as getting no regen at all, I've noticed it only a few times on my bike, and it always seems to be right after I've switched modes. But after a little while operating in that mode, it seems to finally operate consistently. Since I almost always stay in Custom mode, it hasn't happened to me very often.

[Richard230]

My 2012 S also would not provide regen until the battery charge dropped a bit.  My 2014 S does the same thing at 100% charge, then the regen will come off and back on until 99% shows on the meter, after which it functions as intended.  However, I have noticed the charge meter % jumping around a bit when the bike is turned off and then back on.  Usually it will drop a point or two when rebooted after being off for a while.  Once in a while it will jump a point, but I can't find any pattern to the change so I just don't worry about it, as my bike is functioning perfectly otherwise.   

[Patrick Truchon]

That makes sense.  Good to know though.  You figure that they would have put some logic into the regen braking system like:

At start up, test the battery.

• If the battery is above 95% turn regen off until the battery gets below 95%, then turn it on.
• If regen is on and the battery goes above 95% (because of regen), keep in on until the battery reaches 98% then turn it off.

A 3% difference between being turned on and off would probably avoid the pulsing.

Failing that, I guess one solution is to only charge the battery to 100% from time to time.

[Doug S]

A 3% difference between being turned on and off would probably avoid the pulsing.

That's what I was describing when I mentioned "hysteresis" -- that's what us engineers call it when there are TWO thresholds which overlap like that. It's like your furnace thermostat: when you set it to 68 degrees, it switches ON at 66 degrees, then switches OFF at 70 degrees, which keeps it from short-cycling. It's exactly what you're describing, and the Zero engineers should have done it that way.

[DynoMutt]

Another alternative might be to wire in a resistor to convert the regen-reclaimed power into heat when at/near 100%.  This has apparently been done with buses.

[trikester]

Yes to all of the above. But, there is another condition where you won't have any regen and there is nothing in the manual describing it.

SAFETY NOTE! If you come to a complete stop on a down-slope and then start out by just releasing the brake but not twisting the throttle you won't have any regen until you use the throttle once. This is a most common situation when dirt riding with steep hills and stopping to take a photo or gaze at the scenery. It can be pretty unnerving if there is a tight switchback coming up.

I have trained myself to always quick blip the throttle, to re-establish regen mode, when I start out from releasing the brake on a steep down-slope. For some reason, regen is disabled when the bike starts out from a complete stop by coasting without throttle. 

Trikester

[Tater McTatums]

Well I'm glad to hear that the pulsing is normal and the reasons for it make sense. I sort of assumed that's what it was but I figured it never hurts to ask.
In regards to the times of no regen, I tried coming to a stop and starting out again, changing modes, draining the battery down a bit, but the only thing that remedied it was to leave it turned off for a few minutes. Typically when I change modes, even while moving, I can feel and see the change in regen as soon as I press the mode button, as long as I'm not on the throttle when changing. A lot of the times when I'm coming down steep hills I'll just switch it to Eco to maintain speed and regain a bit of charge. There's a ton of deer in my area this time of year. I'd rather have the motor slowing my descent instead of the brakes in the event that I suddenly require them.

[trikester]

When changing modes while riding, the new mode doesn't take effect until the throttle is rolled off and back on again. When I change modes while riding I blip the throttle off to initiate the change.

Trikester