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Makes And Models => Zero Motorcycles Forum | 2013+ => Topic started by: DerKrawallkeks on December 24, 2020, 12:49:11 AM
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Cyclic aging:
- Use (charge/discharge) is best with a warm battery (at least 10°C, up to 40°C improves battery life [A p.139]
- Charge slowly and not to 100% [A p.106]
- Avoid deep cycles, charge often [A p.139]
- Regenerative braking actually improves battery life [A p.139]
- Dynamic loads are not worse than constant loads [A p.140]
Calendar aging:
- Storage should be done cold (down to 0°C) and at lowest SoC practically possible [A p.71]
Yes, 0% would be the best, anything below 55% is good. Especially if you don’t check often, don’t stay too low, as your BMS drains the battery slowly!
- The battery actually recovers capacity if it is stored at low SoC! [A p.130]
(https://i.postimg.cc/WbVY9cx4/degradation-over-So-C.png)
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Hello everybody,
As you know, there’s a lot of conflicting information out there about how to treat your battery.
Many of the instructions are based on reasons like chemistry, usability, comfort, customer-attractiveness. Especially, I strongly disagree with Zeros official instruction to always keep the battery SoC high. It is purely meant to make it easy for the user and avoid warranty-cases, but at the cost of customers wearing out their Zero batteries way quicker than necessary, leading to unnecessary pollution due to toxic waste. I wanted to know the true facts about just the chemistry itself, what is best for the battery cells themselves.
After looking through many many papers on lithium-ion batteries (and especially NMC), I found two very useful ones:
- A: Ph.D. thesis “Aging of Lithium-Ion batteries in electric vehicles” – Dipl.-Ing. Univ. Peter Keil
- B: Paper “Calendar Aging of Lithium-Ion batteries” – Journal of the Electrochemical Society
I called these sources A and B.
They both provide great information based on extensive studies, with no manufacturer involved. Both papers have been published very recently (2016 and 2017). Since both papers are very long and might not be understandable without the necessary background, I wanted to condense the most important conclusions as short as possible into practical instructions. The papers contain much more interesting information, so if you want, I recommend reading them.
Aging mechanisms:
1. Calendar aging: Batteries age over time, no matter if they’re used or not
2. Cyclic aging: Batteries age when being cycled
Using 1000 full cycles causes similar aging as 15 years calendar life. Storage SoC has similar, slightly higher effect than cycle depth.
It is also interesting to note, that if you always charge your battery to 80% instead of 100%, after a several years someone always charging to 100% will have more range since he stores more energy overall, even though his battery degraded more.
This leads to manufacturers making recommendations like Zero does, to simply always keep it charged.
With that, don't forget that a less degraded battery can be charged to 100% anytime and deliver more range than a battery that has always been charged to 100%.
I might keep modifying this post a little bit.
If you have any questions, feel free to ask and I will try to answer them if I have the knowledge.
best regards
DerKrawallkeks
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I thought Zero recommends storage at 60%, and that when the bike enters storage mode (after being left for 30 days) it will actually discharge to that level if it's above it (and if the charger is plugged in it will charge up to that level once the SoC drops enough, to 30% I think). Also with the SR/F and SR/S they only charge to 80% or so by default and require an override to charge to 100%.
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Hey, thanks! That's true, for long term storage zero recommends below 60%. In the diagram I posted, there's a region at 60-70% above which the degradation is much higher. That's the area of the central graphite peak (in another diagram called the differential voltage spectrum). Doesn't matter what that is, it makes sense to stay clear of this area for obvious reasons. The problem is, the central graphite peak can shift around during battery life, so I'd maybe recommend staying below 55%, but Zero probaly knows what they're doing.
My conclusions for storage are for general storage, not just long term. Long term storage is usually done in winter, when battery degradation is low anyway due to the cold, so overall, storage degradation happens much more during riding season, even though the bike is not in permanent storage.
This is mostly meant so you can draw your own conclusions for what you want/can do.
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Are you aware of the actual, per cell, voltage of a Zero Farasis cell when deemed 'full'?
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Hey
according to the datasheet, Farasis cells designed to have a maximum voltage of 4,15V-4,2V.
In the Zero, they're only charged to 4,15V, which is a good measure to improve cycle life.
It does help, but there's a lot to be gained by not charging the battery all the way, if you're after battery life.
(https://i.postimg.cc/1zhR8tfH/charging-voltage-impact.png)
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4.157
The point being that people often look at studies like this without realizing that Zero already sort of caps the charge to 80%, instead of the full 4.2vdc.
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Hey,
4,15V is much higher than 80% SoC on a NMC battery, when 4,2V is considered fully charged.
(https://i.postimg.cc/t4tPRLgY/Voltage-vs-capacity.png)
But it does not really matter what the SoC is, because the voltage is what degrades the cell. It's good they only go to 4,15V
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That might explain why Zeros don't always cut out regen at 100%...
But never, ever store your Zero under 30%. That results in a dead battery very quickly.
-Crissa
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Even in this forum we've seen at least one person whose bike was stored at less than 20% and it never took a charge again... That was supposedly addressed in the most recent firmware updates but it was definitely a wake-up call...
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Thank you DerKrawallkeks, that was quite an informative post. I especially enjoyed reading some details in the A reference. I hope you don't mind me bringing links to these valuable documents in this thread. None of them are behind paywalls.
A: Ph.D. thesis “Aging of Lithium-Ion batteries in electric vehicles” – Dipl.-Ing. Univ. Peter Keil
https://mediatum.ub.tum.de/doc/1355829/file.pdf (https://mediatum.ub.tum.de/doc/1355829/file.pdf)
B: Paper “Calendar Aging of Lithium-Ion batteries” – Journal of the Electrochemical Society
https://www.researchgate.net/publication/304994376_Calendar_Aging_of_Lithium-Ion_Batteries_I_Impact_of_the_Graphite_Anode_on_Capacity_Fade/link/577f8ff208ae69ab8823ff4c/download (https://www.researchgate.net/publication/304994376_Calendar_Aging_of_Lithium-Ion_Batteries_I_Impact_of_the_Graphite_Anode_on_Capacity_Fade/link/577f8ff208ae69ab8823ff4c/download)
I look back at 19'000 km driven on a SR/F and what bothered me most with this technology is the significant loss of power (torque) as the SoC decreases. This, alone, would be for me a reason not to drive below 60%.
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I look back at 19'000 km driven on a SR/F and what bothered me most with this technology is the significant loss of power (torque) as the SoC decreases. This, alone, would be for me a reason not to drive below 60%.
That's really a byproduct of how the inverter is designed and programmed. In order to maintain the kW output the amps consumed has to go up as voltage drops. Ride a LiveWire down to very low in the pack and it still gives full power. I've never experienced what it does on any other electric motorcycle.
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The Harley is drawing less than half the current (300A versus 700A) so I guess more consistent performance is another advantage of using a higher voltage. For Zero to achieve the same they'd need to cut the power to SR or maybe even S levels (at that point you're not gaining anything, just giving up power at the higher SoC) or put the SR/F/S controller (and probably a few other bits) in the lower power bikes.
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The Energicas run even higher voltage than the LiveWire, and the Rinehart inverter is a beast and a half, but the LiveWire still outperforms anything I've seen at low charge. Like Folgers, it's good to the last drop.
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Ride a LiveWire down to very low in the pack and it still gives full power. I've never experienced what it does on any other electric motorcycle.
I never rode one but, now that you mentioned it, I do remember a reviewer mentioning what you wrote.
Funny how at the beginning, when I could test drive a demo SR/F for a couple of days, I thought I would probably not even need a Sport mode. In fact, the first few days I even remained in Eco mode but nowadays I have everything set a 100% and only use the Rain mode when caught in a bad storm.
Anyway, I suppose that getting a decreasing power from a diminishing SoC will in turn increase the overall battery longevity, or so I hope. As can be deduced from the comment of TheRan, one way forward around this limitation would be to increase the battery voltage above 100 V; so no firmware update will ever change that I am afraid.
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Hey,
thanks Zelidar for linking the papers! Luckily they're both free, I just found them on the internet.
@MVetter, sure when the voltage goes down, the battery amps must go up to maintain the same power. But what I think counts for all bikes, both the livewire, Zeros and all the other ones:
No matter the overall voltage and overall amps (livewire having lower amps due to higher voltage), the decision really is wether you design the bike to be able to handle some extra current or not.
To maintain full power: On the zeros, let's say it must handle 700A when full, but it would have to handle 800A when empty. On the livewire, it might be 300A when full and 350A when empty.
It's just a decision wether you spend the extra money to design the components to handle the extra load or not, no matter the absolut currents we're talking about.
What do you think of that thought?
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Oh of course, it's just presumably easier to have a drive train that handles higher voltage than higher current. Zero say the SR/F/S actually have a 900A controller so in theory it can supply the full 83kW down to 91V and 0% SoC is like 95V, so the limit must be the battery (or voltage sag drops it below 91V at a low SoC).
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A: Ph.D. thesis “Aging of Lithium-Ion batteries in electric vehicles” – Dipl.-Ing. Univ. Peter Keil
https://mediatum.ub.tum.de/doc/1355829/file.pdf (https://mediatum.ub.tum.de/doc/1355829/file.pdf)
This PDF is very enlightening. I read most of it. Everyone should read page 141 onward.
So basically keep the battery between 40-80% while riding (if that is enough range for you), and store at 50%. At least that's how I read it. The only part that concerns me is the storage of the battery below freezing, which mine is doing right now.
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Just don't charge it while freezing! ^-^
-Crissa
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Just don't charge it while freezing! ^-^
-Crissa
I discovered last year that if the battery is too cold, it won't charge at all. You have to take it out for a ride so it heats up and THEN you can charge it. The takeaway for me was make sure I put it away in cold weather with enough of a charge that I can actually take it for a ride before recharging it. 30% seems to be as low as you'd ever want to park it for a variety of reasons.
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@Valnar,
Don't worry about freezing temperatures, the Farasis Cells are rated down to -20°C in the official datasheet, so no problem.
Also (that goes for any lithium battery) the electrolyte is not water, but an organic solution. So it does not freeze at 0°C. Storing it around freezing temperatures is the best you can do! It's perfect.
What Crissa said is probably smart, don't charge at low temp if possible, or at least charge slowly.
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Bring you Zero indoors to snuggle warm to charge in cold weather! The electrolyte gets sluggish when cold and works best above body temperature.
-Crissa
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Bring you Zero indoors to snuggle warm to charge in cold weather! The electrolyte gets sluggish when cold and works best above body temperature.
-Crissa
Old thread, but isn't storage different? IOW, you want the batteries a bit cold for long storage, but warm for use.
-Don- Reno, NV
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Hey Don,
I'd say that's right, that's what I concluded in my first post of this thread, after reading the papers.
Just like you said, warm for use cold for storage. With very slow charging, it doesn't matter much I think :)
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Hey Don,
I'd say that's right, that's what I concluded in my first post of this thread, after reading the papers.
Just like you said, warm for use cold for storage. With very slow charging, it doesn't matter much I think :)
Yeah, the way I think of it is that cold turns the battery more "off". That way, longer storage, less drain.
A warm battery is more "on" and ready for performance, but more drain when not in use.
-Don- Reno, NV
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Bring you Zero indoors to snuggle warm to charge in cold weather! The electrolyte gets sluggish when cold and works best above body temperature.
Old thread, but isn't storage different? IOW, you want the batteries a bit cold for long storage, but warm for use.
Yes, that doesn't contradict what I said.
If you're storing a battery, you're not charging/discharging it.
-Crissa
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Yup. Like you said Crissa, the electrolyte looses its ability to move ions, the colder it gets. Also they can't move as well inside the anode/cathode material.
So for quick charging, it makes sense to have it warm.:) for slow charging (0,1C) with the onboard charger, it probably doesn't matter
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Well, it needs to be above freezing. You need the ions to move to charge, and if they don't move at all, well, that's bad, too.
-Crissa
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Yes, but the electrolyte doesn't freeze. It's not like at exactly 0, charging or use becomes impossible. The electrolyte is organic:)
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Yeah, it's worse: it doesn't freeze evenly.
-Crissa