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[Manzanita]

What, there isn't a recent thread where I can whine and complain about range!?! I guess I'll have to start one!

Greetings Zero owners, I'm back, and as whiny as ever.

I had sold my 2014 Zero S with power tank two years ago... and about a month ago I bought it back, with only a few hundred miles more on it, now at about 24,000 miles (bought it back for the same price I sold it, $5k). My reasoning is I now I have new job that is 25 miles from my house, and they have an entire line of free chargers in front of my building, mostly unused. I thought for sure the bike could go both ways on a single charge and thus I'd be getting "free gas" (and could justify another motorcycle!)

Well, uh, long story short, both times I tried to do a full loop on a single charge (50 miles total), even riding conservatively (55-60 mph or slower, with 75% at that speed and 25% slower) I ended up with the bike showing zero percent charge 5+ miles before reaching my destination. When I did it riding back to work it was super stressful because if it died I would have been late to work and it is a new job. Way more exciting than I needed it to be, but I did make it to work. I was pissed, because I was riding very conservatively, and (at least on this and most days) don't go above 60 mph. (Btw I weight 165 lbs and the bike has a windscreen)

Today riding back home I had quite the experience:

The bike went from 47% SOC (102 volts) (I had stopped half-way for 1+ hours on my way home) to 3-4% SOC (voltage unknown) in about 2.5 miles going 60 mph on flat ground(no exaggeration) and I still had 8 miles and a 2000+ foot climb to get back home. Basically I rode 5-6 miles uphill with the display showing 0% SOC, going 45-55 mph, with some power limiting, but still able to go 45 mph up until the last mile or so.

I made it home without the bike dying... but I wanted to know how large the "empty tank" was... as an experiment, I kept going up the hill, figuring I could turn around and roll back down even if it dies now. So it went about a mile more and it finally died. When I got home the phone app showed the battery at 97 volts (sitting for an hour or so it went up to 98 volts and showed 14% charge).

So is this normal behavior? I looked up the graphs on the wiki page ( https://zeromanual.com/wiki/File:Soc_vs_voltage.png ) and I guess that's what it shows, and the bike is shutting off at 97 volts. So that is a hard limit? I have the memory of people on the forum saying that 87 volts was the magical "empty" voltage number. No?

Actually I have been taking screenshots of my app with the bike having gone 25 miles (either to work or to home) and voltage ranges from 104-106 volts after 25 "easy" miles.

Some questions:
1) is my apparent rapid discharge while riding normally (47% to 3% in less than 3 miles) a sign of a battery problem or just some weird SOC calculation issue? 

2) How about going from full charge to 105 volts in 25 "medium" miles (55 mph)?

3) I have screenshots showing 14% SOC at 98 volts and on a separate occasion, 15% SOC at 103 volts. why such a big difference in voltage at the same SOC?What other parameter figure into the SOC number? Cell balance?

4) Reading the wiki page on the Zero battery made me realize that even if I can do both directions on a single charge, it would make sense to charge the bike at home and at work to improve battery longevity... or is there enough buffer to where the effect of riding to 97-98 volts is not going to make a major difference in battery longevity? The cost and trouble are actually minimal, mostly I'd just be losing bragging rights of saying I don't pay anything for "gas"...

5) Will my SOC display become more accurate now that it "knows" how far the bike can go before hitting the shutoff voltage?

Thanks in advance,

-Alan

[MVetter]

What's your cell balance, listed in milliVolts (mV), showing in the app? Check the app at 100%, 50%, and at 0% or as low as you want to get. Report back here.

[Manzanita]

From my app screenshots:
At 97 V = cell balance 219 mV
At 98 V = 89 mV
At 102 V = 14 mV
At 105 V = 58 mV
At 106 V = 12 mV
At 115V = 2mV
(all measurements while not charging)

So cell balance is a measure of the worst cell voltage difference, and so indicates when a cell is going bad? These don't seem that bad (considering 0.2 volts of 100 volts is a 0.2% difference). What is your take?

The bike is taking a full 10 hours to charge (with one external Delta-Q, onboard charger is dead) showing ~900 watts on the app = 10 x 0.9 = 9 KWh. Maybe subtract 10% for charging efficiency and say 8 Kwh battery charge is 100% full from empty... how accurate is that as a measure of true battery capacity? How does this compare to other bikes?

[MVetter]

It's an indicator of a bigger problem. The worst you've recorded may be 219mV, but it could be an even greater disparity. A friend of mine had a pack with a bad cell that would basically hit a 500mV spread at 50% SoC; he only had half a usable pack.

I think you might be at the stage where it's worth downloading your BMS logs for parsing and seeing just how bad it might be. Fire up your app and download the logs. Send the files to this website: https://home.hasslers.net/zerologparser/

From there you can start looking through and becoming familiar with which cell(s) are acting up and how badly.

[rgutt]

Your battery is leaving the conversation. That spike to 58mV at 105V shouldn't be there. And though I expect cell imbalance to increase at depth of discharge, pushing 100mV, or in your case, exceeding 200mV, isn't good.

If the battery showed good characteristics before you sold it, it's likely your intermediate owner didn't do a good job of storing it, either holding it at excessively low or high states of charge. Either one is detrimental to battery health, and since the battery is already 9 years old ...

[Manzanita]

I think you might be at the stage where it's worth downloading your BMS logs for parsing and seeing just how bad it might be. Fire up your app and download the logs. Send the files to this website: https://home.hasslers.net/zerologparser/

From there you can start looking through and becoming familiar with which cell(s) are acting up and how badly.

Thanks your input and help MVetter!

Here is the section of the BMS log of the 5 minutes where I went from 47% to 4%, riding at 55mph on a fairly flat road:

03798     07/20/2023 20:51:18   Discharge level            011 AH, SOC: 47%, I: 27A, L:3524, l:3578, H:3558, B:034, PT:039C, BT:043C, PV: 99102, M:Bike On
 03799     07/20/2023 20:51:18   SOC:4450,8284,11958,22770,48,36,47,22
 03800     07/20/2023 20:51:18   Discharge cutback          82%
 03801     07/20/2023 20:51:18   186A
 03802     07/20/2023 20:52:18   Discharge level            012 AH, SOC: 42%, I: 18A, L:3474, l:3538, H:3545, B:071, PT:039C, BT:043C, PV: 98492, M:Bike On
 03803     07/20/2023 20:52:18   SOC:4723,8057,12232,22770,47,25,42,26
 03804     07/20/2023 20:52:18   Discharge cutback          69%
 03805     07/20/2023 20:52:18   157A
 03806     07/20/2023 20:53:18   Discharge level            012 AH, SOC: 33%, I: 15A, L:3419, l:3489, H:3534, B:115, PT:040C, BT:043C, PV: 98053, M:Bike On
 03807     07/20/2023 20:53:18   SOC:5029,7451,12540,22770,45,12,33,28
 03808     07/20/2023 20:53:18   Discharge cutback          54%
 03809     07/20/2023 20:53:18   121A
 03810     07/20/2023 20:54:18   Discharge level            012 AH, SOC: 25%, I: 20A, L:3378, l:3459, H:3515, B:137, PT:040C, BT:043C, PV: 97374, M:Bike On
 03811     07/20/2023 20:54:18   SOC:5290,7008,12802,22770,44,7,25,31
 03812     07/20/2023 20:54:18   Discharge cutback          51%
 03813     07/20/2023 20:54:18   116A
 03814     07/20/2023 20:54:34   Discharged To Low          012 AH, SOC: 22%,         L:3332,         H:3493, B:161, PT:040C, BT:042C, PV: 96593
 03815     07/20/2023 20:55:18   Discharge level            013 AH, SOC: 14%, I: 23A, L:3305, l:3419, H:3479, B:174, PT:040C, BT:042C, PV: 96077, M:Bike On
 03816     07/20/2023 20:55:18   SOC:5692,6589,13205,22770,43,2,14,38
 03817     07/20/2023 20:55:18   Discharge cutback          40%
 03818     07/20/2023 20:55:18   91A
 03819     07/20/2023 20:56:18   Discharge level            013 AH, SOC:  4%, I: 31A, L:3204, l:3416, H:3429, B:225, PT:040C, BT:042C, PV: 94192, M:Bike On
 03820     07/20/2023 20:56:18   SOC:6156,6412,13675,22770,40,1,4,48
 03821     07/20/2023 20:56:18   Discharge cutback          22%
 03822     07/20/2023 20:56:18   49A

I have no idea how to interpret this.... what is this telling me?

Is there a guide to interpret the line "SOC:6156,6412,13675,22770,40,1,4,48" and the line
 "Discharge level            013 AH, SOC:  4%, I: 31A, L:3204, l:3416, H:3429, B:225, PT:040C, BT:042C, PV: 94192, M:Bike On"

Although I can't be certain the previous owner was keeping it at 60%, he was aware that that is the best charge to store it at, and he said he was doing it... the first few years I was keeping it charged to 100% and plugged in when not in use, since that is what Zero was recommending... but in terms of discharging it to the lower SOC's that was rare, I pretty much kept it above 30% SOC. Most the mileage on the bike was from a 12 mile (each way) commute, which was pretty easy to do that round trip and get back home with 40% SOC.

Is having the power tank an issue? How does the power tank cells appear on the BMS log (or does it)?

[MVetter]

I can break down some of it because I remember some of it but not all of it. Let's go over the part you highlighted.

Discharge level            013 AH, SOC:  4%, I: 31A, L:3204, l:3416, H:3429, B:225, PT:040C, BT:042C, PV: 94192, M:Bike On

Pack capacity listed as 13 Amp Hours (AH)
State of Charge (SoC) 4%
I: value might be how much current the bike was pulling at that time. 34 Amps? Not sure.
L: value is the cell with the lowest voltage. In this case 3204 or 3.204 volts.
l: shows median cell voltage levels 3416 or 3.416.
H: shows the highest cell value at 3429 or 3.249 volts.
B: is the balance value of 225 which is the disparity between the lowest and highest cells.
I believe the PT and BT values show the coldest and hottest cells in Celsius.
PV stands for Pack Voltage of 94.192vdc.

In a perfect world you want all your cells within a few mV of each other. At the top end of the pack, when the bike attempts a balance cycle, it tries to get all the cells as close as they can. A pack is only as good as its weakest cell, because it cannot allow cells to dip outside the acceptable voltage parameters. Even if all your other cells are in great shape, if one guy is at the bottom end cutoff of 3.2vdc, which is below Zero's acceptable parameters, the bike is going to basically say "sorry this is below where we can go we have to stop".

Really if you just watch that B: value you can see the delta between the cells grow at an uncomfortable rate. In a perfect world it wouldn't really change at all, but at 47% you've got a 34mV imbalance, and by 33% that has grown to 115mV. It's basically quadrupled.  The larger problem is that Zero's batteries are fully potted in epoxy, so you cannot just disassemble a pack and service a cell. I'm sorry to say but your pack is on its last leg. Basically within 5 minutes one of your cells dropped like a stone from 3.524vdc to 3.204vdc while the rest of them didn't. They held at 3.578vdc to 3.416vdc.

[Manzanita]

Your explanation clarifies so much!

3.2 volts per cell is really what "empty" is. I understand that the differential number is just another way of stating that, but conceptually it is much more clear to me if you see that voltage as the "floor" where the bike is on the verge of shutting down. The the 3.2V cell limit was the missing piece of info for me.

Here is what the log shows around when it died: 03851     07/20/2023 21:04:00   0x05 0xd9 0x0b 0x8d 0x0d 0x2a 0x29 0x75 0x7d 0xf2 0x00 0x00 0xee 0x71 0x01 0x00 0x00 0x00 ???
 03852     07/20/2023 21:04:00    - DEBUG: Cells - 3433, 3338, 3437, 3344, 3352, 3445, 3451, 3447, 3451, 3469, 3386, 3450, 3440, 3415, 3451, 3297, 3398, 3375, 3403, 3286, 3033, 3338, 3370, 3415, 3361, 3309, 3417, 3391
 03853     07/20/2023 21:04:18   Discharge level            022 AH, SOC:  1%, I: -1A, L:3165, l:3209, H:3519, B:354, PT:042C, BT:040C, PV: 96626, M:Bike On

Functionally what this means is I have a bike with significantly reduced range. But with my one-way commute 25 miles and with the ability to charge on both ends, does this mean the battery pack is going to continue to rapidly degrade to where I can't do this commute, or will I be able to go years doing this 25 mile commute (charging at both ends) with no problem?

[MVetter]

354mV, oof. Keep in mind while that, yes, you've got that 3.2 value in your head as empty it's not quite that simple. That's a good general target or starting point, but it can vary with cell chemistry and also any soft caps imposed by the manufacturer.

For example the BMS in Zero bikes likes to keep the cells between 3.39vdc and 4.157vdc. You can tell because there are 28 cells in series, and those values correspond to the empty/full values.

3.39 x 28 = 94.92 vdc aka ~0%

4.157 x 28 = 116.396 vdc aka ~100%

You *could* attempt to do a little more digging. See I don't know if the weak cell is in your Monolith or Power Tank. You could attempt to narrow that down because if you found the Power Tank to be the culprit you could, pardon my French, just toss that bitch. Not literally, though. If you feel so inclined, pop your tank plastics off and disengage the giant Anderson connecting the Power Tank. You may need to find the blank cable end that goes on the wiring harness when people don't have Power Tanks in order to operate it; I can't remember. There are settings in the MBB where you can disable that and I had that overridden on my SR.

Anyway, if this behavior persists with the Power Tank gone, it indicates the problem is in your Monolith and there's very little you can do other than carefully ride it using the top half of the pack. If the problem is in the Power Tank, get rid of that and your range should jump back up.

[Manzanita]

Thanks again for your input, I appreciate it. Does anyone else have any experience or data regarding bikes that have this issue--do they slowly degrade, or does the existing problem mean it is going to rapidly deteriorate to being unusable?

As-is, I am okay with having 25 miles of real range, that's all I need. Below that it is a paperweight for me, but I suppose it may have value to someone who only needs 10 mile range... as long as the rate of range degradation isn't quick, it is usable.

I guess I will find out, and will report back here...

[DerKrawallkeks]

The only thing I can add here, is that my bike (2013 S with a 2015 battery) keeps cell balance to 10-20 mV at 97 V, and only If I go lower it'll start to drift significantly. I think unfortunately at least one cell in your battery is dying..