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[Doug S]

Well, I did it. I wanted to see if I could get from my home in El Cajon, CA up to Julian (a local mountain resort/tourist trap/apple pie hotspot) and back on my 11.4 SR, and I can...but just barely. After sweating out the last ten miles or so of the 90-mile roundtrip, doing 35 mph in 50 mph zones, I wound up pushing the bike the last 100 yards or so to my driveway. Fortunately it is a light bike, it was only 85 degrees and god knows I need the exercise. I won't do it again (although PlugShare tells me there's a "Don's Market" in Santa Ysabel that has a CHAdeMO/J1772 recharging station, which makes them sound pretty EV friendly....hmm....).

I'm a little concerned that discharging the batteries that deeply may have done some damage, so I'll be watching pretty closely for several days to see if my commute sucks the batteries down any faster. I think it's fair to assume the engineers don't allow the batteries to discharge into real danger territory, but all my years of battery experience (I'm an EE and I do design with batteries occasionally) tell me that the deeper the discharge, the shorter the battery life. I doubt a single event would do much damage, however. I normally treat my batteries very well.

Why do we seem to feel the need to do that? Is it just human nature that when confronted with a limit, we feel compelled to push it? I've ridden up to Ramona, part way up the hill, several times, and it's a great, enjoyable ride. I don't even care that much for their apple pie (they oversweeten it there for my taste), why did I feel the need to go up to Julian? I just had to know, I suppose.

[kensiko]

At 0% SoC I assume the battery is still at 1.4 kWh so about 12%. I think it should be safe but you need to plug it as soon as possible, which is what you did.

[scZero]

Its not bad for the battery discharging it low.  It is if you:

-Let the battery sit at the low charge (SOC) for a long time, more than a day. You really want to charge it ASAP.
-Where very hard on the throttle pulling hard amps out of the pack at the low SOC
-Was very very hot out and the pack just sat for  hours and hours.

Honestly the packs need to be fully charged and discharged (at least down to 10-20%) so that the BMS has the true full/empty capacity of the pack.

[trikester]

(although PlugShare tells me there's a "Don's Market" in Santa Ysabel that has a CHAdeMO/J1772 recharging station, which makes them sound pretty EV friendly....hmm....).

I drive past that Don's Market every time I go from my home on the coast to my desert cabin, which is quite often. I should stop in and see if I can locate the charging station.

At this point I don't have quite enough capacity (Zero FX) but almost, to ride from my cabin, up through Julian (43 mi), and down to Santa Ysabel (another 7 mi). But if I do in the future that could be handy. Of course I would have to have the ability to use that fast charge. My round trip from the desert side would be close to the same distance that you did.

Trikester

[Doug S]

...that could be handy. Of course I would have to have the ability to use that fast charge.

Somebody really needs to do something in Ramona; that would make the whole mountain much more accessible to us EVs. It might even get me off the fence about plopping $1700 down for the CHAdeMO adapter. Being able to reasonably ride up to visit my folks/brother in OC isn't QUITE getting me over the hump about spending that kind of money, especially given that many of the CHAdeMO units seem not to be useable.

[dkw12002]

Been there, done that. If you leave the bike on and push with eco set on regen with off-throttle, you can build up some regen after a bit too. After pushing and probably more important...coasting a bit after the bike stopped... it got recharged a little and I was able to ride the Zero S a little more (1 block) after a reboot.  Sort of like in The Princess Bride where Westley was only MOSTLY dead instead of all dead.

[Doug S]

Been there, done that. If you leave the bike on and push with eco set on regen with off-throttle, you can build up some regen after a bit too. After pushing and probably more important...coasting a bit after the bike stopped... it got recharged a little and I was able to ride the Zero S a little more (1 block) after a reboot.  Sort of like in The Princess Bride where Westley was only MOSTLY dead instead of all dead.

Hm. If you leave it turned on, the headlight stays on, which is a 50W draw IIRC. Also the 12V converter, the dashboard, all the controllers...let's be conservative and say 60W total. So in addition to moving the bike, you have to supply an extra 60W just to break even, let alone some more to provide any regen. Lance Armstrong, at his drug-fueled maximum, could provide maybe 700 watts of power for a fairly short amount of time. This out-of-shape 52-yo would have a hard time just breaking even. Obviously a downward slope helps, but I was headed uphill, which would tip the balance even farther against me.

But I abbreviated my experience. Here's the full details of the end of my ride: At maybe 1000 yards from home, I still had 3% showing, which I felt pretty good about...I'd been losing a percent in maybe a half mile or so for a while. But as I turned right and started ascending the penultimate (not very steep) hill, the display immediately dropped to 2%, and I had very little power under my right hand. That seemed fine; by this time I had just a few hundred yards to go, and I figured the controller was cutting back power to help me stretch the last little bit of my range. But within a hundred yards or so, it ticked to 1%, and I lost all power, coasting to a stop maybe 300 yards from my driveway. Honestly, I felt a little offended that the display still showed I had 1% SoC available, but it wouldn't give me anything. But there were only maybe 100 yards of mild uphill, followed by 30 yards or so of mild downhill, and then a couple hundred of mild uphill to my driveway. Not terribly daunting, but first let's see if I'm truly empty. I turned the key off, then on. Still showed 1%, no response to the throttle. Power cycle it again, still 1% and no response. Otay, Panky, time to get off and start pushing, for which I turned the key off. After reaching the top of the first hill, just 100 yards or so, I got back in the saddle, turned the key on....and it gave me power! I stayed on it, not wanting to upset anything, through the few yards of downhill followed by the couple hundred of uphill to my driveway. It stopped again just as I turned into my driveway, but at that point I was overjoyed to push it the last 10 feet.

So. It certainly didn't regen while I was pushing it uphill with the key off. I'm thinking that while I was pushing it, in the absence of any load, the cell voltage recovered a tiny bit (which batteries do), passed some threshold and the controller gave me just a little bit of a last gasp. I'm wondering if your experience was similar?

[ultrarnr]

Next time you have a very low SOC left take a look at some other numbers. Like how many miles you have went and the Wh/mile. Multiply that to see just how many Kilowatt hours you have really used. I think there is a chunk of that battery you are not going to be able to touch so just because you think you have completely discharged your battery you really haven't. The BMS is not going to allow you to completely drain that battery. Zero has a 5 yr/ 100,000 mile warranty on the battery pack. I am confident they realize people are going to drain their battery's down from time to time and they they aren't going to take a risk on that damaging the battery. Having a BMS that shuts the bike down completely before damage can occur due to low SOC is one way to do that.

[Doug S]

I am confident they realize people are going to drain their battery's down from time to time and they they aren't going to take a risk on that damaging the battery. Having a BMS that shuts the bike down completely before damage can occur due to low SOC is one way to do that.

Agreed. I'm an EE and I wouldn't even consider NOT limiting the discharge to some reasonably safe value. I checked the app this morning, and it showed the battery SOC to be 100%, and gave my kWh as 10.82 rather than the 11.4 "nameplate" value, but it also showed only 92 Ah in the battery pack. Since I know the capacity of the cells in the pack is 25 Ah (http://electricmotorcycleforum.com/boards/index.php?topic=3231.0), and there are four in parallel, 28 in series, I should show 100 Ah of capacity in the pack. I'm guessing the 8 Ah difference is the reserve below which the BMS will not allow the batteries to be discharged.

[Richard230]

When I ran my 2014 power-tank S down to empty, the display read 0% and it came to a complete stop without any warning.  I was going uphill at 25 mph and the bike just stopped.  After letting it sit for 30 seconds, it would move another 20 feet.  I tried pushing it, but the hill on my street is pretty steep and I just could not push the bike more than a few feet without having a heart attack.  Eventually, I made it up the hill and into my driveway by stopping to let the battery recover and then moving 20 feet, when it would die and I would wait for the pack to recover again.  I did this about 10 times and managed to get home.  But it was really close to having to walk home, get a long extension cord and finding a neighbor who would let me plug into their outlet for 30 minutes. I got lucky that day.

[dkw12002]

Battery recovery rather than recharging is probably what I experienced too when I was able to go a block after the bike stopping even though I pushed and coasted. On my 2011 Zero S, when I would stop with say 3 bars showing, then after a while get back on the bike and boot up, 4 bars would be showing often. Was that battery recovery too?

[trikester]

But it was really close to having to walk home, get a long extension cord and finding a neighbor who would let me plug into their outlet for 30 minutes. I got lucky that day.

I guy I knew owned a Stanley Steamer in his antique car collection. He told me that they didn't condense the used steam and recover the water to use again. It suffered from very low mileage per gallon of water. So it was common practice in the old days for the driver to carry a container that he could use to stop at people's homes and ask for water for his boiler.

Maybe our electrics are becoming the modern equivalent of the Stanley Steamer. Will we be carrying 500 foot extension cords instead of water cans?

Trikester

[ut-zero]

I ran out of electrons one town over and had to push the bike to a construction site.  Asked them if I could plug in for half hour or so and they didn't mind.  It's good to know exactly where empty is, but I've been a little more careful about my range since then.

[Richard230]

But it was really close to having to walk home, get a long extension cord and finding a neighbor who would let me plug into their outlet for 30 minutes. I got lucky that day.

I guy I knew owned a Stanley Steamer in his antique car collection. He told me that they didn't condense the used steam and recover the water to use again. It suffered from very low mileage per gallon of water. So it was common practice in the old days for the driver to carry a container that he could use to stop at people's homes and ask for water for his boiler.

Maybe our electrics are becoming the modern equivalent of the Stanley Steamer. Will we be carrying 500 foot extension cords instead of water cans?

Trikester

When I was in high school one of my friend's dad had a sideline overhauling Stanley Steamers in his garage.  I had no idea those things were so big - and quiet, too.  But I do recall the amount of steam that followed the Stanleys.  The humidity in the neighborhood must have gone up 25% when those things were being tested out.   

[benswing]

As I've followed this thread I've been trying to figure out whether I prefer a little wiggle room after the indicator reads "empty" (like on my bike) or whether it would be better to know exactly when the battery will stop supplying juice (like on the 2013+ bikes). 

For example, on my latest trip (on a 2012 Zero S) I went 12 miles past the last battery bar indicator without any diminished performance.  (I was taking it very easy and tested to see if I could still accelerate.)

I do like having a little extra distance to go after that last battery bar is gone, but there is also something nice about being more confident in the actual range of the bike.