Video on 80% charging, "Good or Bad?"

[MetricUSA]

They suggest a large final charge...

 

https://www.autoevolution.com/news/li-ion-batteries-in-electric-vehicles-will-last-a-lot-longer-thanks-to-a-neat-trick-178697.html

[mrelwood]

4 hours ago, MetricUSA said:

They suggest a large final charge...

 

https://www.autoevolution.com/news/li-ion-batteries-in-electric-vehicles-will-last-a-lot-longer-thanks-to-a-neat-trick-178697.html

They actually talk about a quick large discharge current at the end of the charge.

[RagingGrandpa]

5 hours ago, MetricUSA said:

https://www.autoevolution.com/news/li-ion-batteries-in-electric-vehicles-will-last-a-lot-longer-thanks-to-a-neat-trick-178697.html

The method for reactivating the lithium anode involves providing a big surge in discharging current at the end of a charge cycle. This moves the isolated lithium ions toward the anode. The higher the discharging current, the faster they move and the more efficient the process is. The results of the study have been validated with multiple test batteries and through computer simulations.

The study showed the lithium ions in a real battery could be recovered by simply changing the charging protocol. This should be enough to extend a battery’s life by as much as 30%. Recycling the lost lithium ions also lowers the risk of the battery catching on fire. This could be a real boon for second-life batteries used in residential energy storage systems.

 

An interesting concept... but we'd need more specific information to apply this to EUC batteries safely, in order to give time for balancing to complete. An important step in balancing is the 'rest' time after the charger is disconnected, where the bleed resistors finish lowering the high-voltage cells.

On 3/22/2021 at 10:38 AM, RagingGrandpa said:

so:

• undervoltage cells benefit from leaving the charger connected longer (extend CV phase)
• overvoltage cells benefit from letting the pack rest after disconnecting the charger

https://forum.electricunicycle.org/topic/22109-passive-balancing-a-simulation/?do=findComment&comment=360341

[mrelwood]

4 minutes ago, RagingGrandpa said:

An interesting concept... but we'd need more specific information to apply this to EUC batteries safely,

Since the aim of the concept is to prolong battery lifetime, there are no reasons to apply it to EUCs any more than there are for 80% charging. We simply don’t use the batteries long enough for any prolonging to matter.

[Tawpie]

It's important that in the full writeup, they started with an island of isolated lithium in the battery and that the big discharge moved the lithium island 'nanometer by nanometer' by (presumably) redepositing lithium on the end closest to the anode. It's an interesting theoretical exercise but also not ready for prime time.

Edited January 11, 2022 by Tawpie
clarify by using the same terms as their paper

[lagger]

I have looked the video and have some points. Layman can damage their cells this way but I will try to explain why its not utterly bad idea and when you can benefit from it.

Most of the Li-ion cell datasheet cycles values are around 500 cycles to achieve 80 % State of Health (SoH). 1 cycle means an energy discharged that equals to rated energy so 10 times discharge of 10% SoC equals to 1 cycle. The aging of the cell is non-linear but until 80 % it goes pretty much linear. Around 80% it starts to go down the hill. Also the internal resistance wont be good so you might be closer to cutoffs and wont get the torque you need with battery of low SoH.

Other thing is that for example my V10 does only 30 km on 1 charge. I have already 5500 km on that wheel so thats roughly 200 cycles and I am not really a daily commuter. I know people that have 15000 km on a single wheel.
But yeah If you have a wheel that has a big reserve in power and range maybe losing some SoH wont make you concerned and wont affect your commuting but on the other hand you could also very easily keeping your battery happy (when you know how to). I am riding like 90 % of the V10 capabilities so I am limited by its performance at the moment.

In your graph you say that the companies give some reserve for the cells so you are not discharging the cells from 100 %-0 % but rather 100 %-20 %. Thats not such in many cases.

Typical Li-Ions have characteristic like this (its example):
102 %  4.25 V (not best for longetivity)
100 %  4.2 V
5 %      3.0 V-3.3 V (this is always tricky part)
0 %      2 V

Now think about the imbalance between cells in battery pack and the fact that most of the EUCs let you go to something like 3.1-3.3 V. Its like 95 % of available energy in the cell and the imbalance might make that you completely discharge some of the cells -> permanently damaging them -> damaging them even more in next cycles (positive feedback loop). So yeah I agree with you in video but the case studies are inconclusive because it wasnt mentioned how deeply they were discharging how they behaved to the battery. Of course not balancing at all is a battery kill in long run and also some thermal runaway probability is increased. Some packs are better some worse, some might be nicely balanced and will take longer for the deviation to be problem.

Another thing is how to determine something like 80-90 % charge. When fast charging this might be little bit problematic. When charging normally its easier but still you need to be sure that your EUC reports realistic SoC values. If you are charging an EUC and the SoC over time between (20-90 %) doesnt look close to linear either the charging is "interesting" or the mapping of SoC to voltage is way off. But in general if you charge to 80-90 % its not that big of a deal but charging only to 70 % because of bad SoC indication would cost you some useful energy.

Regarding the tips in the end, I add some more that are missing and extremely important:
One of the biggest thing is not to deep discharge the battery if not necessary (going bellow 30 %) https://www.cedgreentech.com/article/how-does-depth-discharge-factor-grid-connected-battery-systems. Charge it back to some reasonable value if possible. Lets say if I am commuting I know that the wheel would make the ride to work and back on 1 Charge but in the long term I would unnecessary deep discharge (stress) the battery and lose SoH.
Also you shouldnt charge the battery when its too hot just after some heavy dynamic ride. Its best to wait an hour. They dont like high temperatures overall for longetivity so keep them cool if possible and dont let them burn when sun is shining.
You can normally charge the lithium cells above 5 Celsius but never bellow freezing. Normally people wont have their EUC in these freezing conditions. When coming back from a ride when freezing that doesnt mean the battery is also freezing.

So to wrap it up.

It can certainly help but wont do for many and maybe not significantly enough. If you know what you are doing and think that you can benefit from than you can do it.
But you need to have in memory that you should NOT deep discharge the cells because they might not be perfectly balanced and it also doesnt help them in long run. Also let the BMS balance the cells after some cycles by charging to 100 % and letting it there for few hours. How many cycles is a tricky question. Some low quality packs might need to be balanced every 3-5 times. Some might be well OK for 10 times. It also depends how deep you discharge your battery. When discharging only upper 50 % you can go with imbalanced cells little longer. I am doing it like 5-10 cycles on my pack and the battery life is still good after 200 cycles.

[mrelwood]

1 hour ago, lagger said:

I have looked the video and have some points.

Thank you, both for watching the video as well as for your comments.

I haven’t been able to confirm how the charge cycles should be calculated when stopping at 3-3.3V, so you could be right in that riding the battery all the way to empty is actually 95% of a full cycle, and not 80% like I suggested. Although, this doesn’t change how people should approach 80% charging.

If all goes well, your V10 will be past 14000km once you have reached 500 full charge cycles. I think that’s an incredibly respectable amount, and still have 80% of the SoH left!

 Worth reminding that my 840Wh 16S had it’s first battery failure at 4000km because I often charged only to 80% and only balanced the battery every 10th charge.

 And someone had a battery failure on their 1556Wh 18XL at 2000km because of only charging to 80%.

 

I’ve heard a few people mention the damage that batteries can get from being discharged to 3.15V, but I haven’t yet read anything that would’ve convinced me that I should take it into account when using my wheel.

And more importantly, I have deep discharged both my previous MSX (14000km) as well as my current V11 (6300km) numerous times, many times far enough for it to completely prevent me from riding any longer. Despite of this, the range figures I get haven’t decreased enough for me to notice.

 So, I understand the theory behind the warning, but unlike with 80% charging, I have yet to see anything that would suggest “deep discharging” to actually be harmful for an EUC.

[lagger]

As I mentioned due to covid and current EUC situation I am riding my V10 on its peak performance so I am really trying to keep it happy especially if it doesnt cost me anything and know what I am doing. I understand the argument. For someone the benefit is not significant or its better not to do it if unsure. There are many users with different needs. Wouldnt say its generally bad.

Regarding deep discharge I posted link in that comment. There is also physics / chemics behind that.

Many people do deep discharge and its one of the worsts things to do and easiest to avoid together with unnecessary exposing the battery to high temperatures.

Another thing is as you mentioned with balancing. Going to 0% SOC (realistically the cells will be around 5%-10%) on a wheel mean that slight imbalance will degrade the already weak cells so thats another reason why not to go that deep with a (multicell) batterypack.

Anyway, even  iPhone will give you notification when your battery is at 20 % so you dont deep discharge. It is really a fact that you can read a lot about.

[mrelwood]

1 hour ago, lagger said:

It is really a fact that you can read a lot about.

I’m sure I can, just like I can about 80% charging. But until I’d clearly see the actual harm of deep discharging in EUCs as opposed to my experience which tells me that it doesn’t seem to be very harmful at all, it doesn’t make sense for me to start warning others about it.

Btw, I consider the iPhone’s 20% and 10% battery warnings to be in place to prevent the phone from turning off without notice. Just like a car warns you when the gas tank gets below a certain level, yet it doesn’t harm the car one bit. The iPhone manual doesn’t warn about running the battery below 20%. Though I’d be interested in knowing what the actual 0% and 100% voltages are on mobile phones.

Edited April 13, 2022 by mrelwood

[lagger]

But Apple also charges based on your usage pattern. It will charge only to something like 80% and then wait until it expects usage and charge the last %s.

Anyway, look at figure 6. it gives some nice data showing different life based on different depth of discharge for Li-Ion batteries
https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

[mrelwood]

21 minutes ago, lagger said:

Anyway, look at figure 6. it gives some nice data showing different life based on different depth of discharge for Li-Ion batteries
https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

Did you notice the units on the X axis? Just like the benefits of 80% charging, at the expected lifetime of 500 cycles (14’000km for V10, 38’000km for RS/V12, 70’000km for Sherman) the differences are very very small. I don’t see it as a viable danger of preliminary battery wear even on paper, let alone in practice. Zero reason for me to act upon.

[Tawpie]

1 hour ago, lagger said:

But Apple also charges based on your usage pattern. It will charge only to something like 80% and then wait until it expects usage and charge the last %s.

This is 'correct' for a single cell battery, but not for a pack of batteries stacked in series. That's where we were initially misinformed... you cannot treat our packs the same way you treat a single cell, our packs need a different protocol.

[lagger]

4 hours ago, mrelwood said:

Did you notice the units on the X axis? Just like the benefits of 80% charging, at the expected lifetime of 500 cycles (14’000km for V10, 38’000km for RS/V12, 70’000km for Sherman) the differences are very very small. I don’t see it as a viable danger of preliminary battery wear even on paper, let alone in practice. Zero reason for me to act upon.

The scaling is interesting but the behavior is clear. There is significant improvement and if it wasnt, why EVs are utilizing the battery pack only between 85-25%?

4 hours ago, Tawpie said:

This is 'correct' for a single cell battery, but not for a pack of batteries stacked in series. That's where we were initially misinformed... you cannot treat our packs the same way you treat a single cell, our packs need a different protocol.

Yes, thats why I wrote that long text. Its individual and you should not do that many consecutive times. Importantly when doing it, you shouldnt deep discharge the pack. Because of that imbalance the deep discharge can be a killer in long run as the pack utilization is like 90-95% in our EUCs so you can easily fully discharge -> kill the weak cells. So deep discharge is something where I would be very careful when it comes to EUC battery packs.

[mrelwood]

7 hours ago, lagger said:

The scaling is interesting but the behavior is clear. There is significant improvement

… only after well past what anyone has put their EUC through. At the common range of 100-200 cycles the improvement is minute. That makes it detached from the realities of owning and riding an EUC.

7 hours ago, lagger said:

and if it wasnt, why EVs are utilizing the battery pack only between 85-25%?

- The battery for an electric car can cost more than $10000.

- An electric car aims for a lifetime of several hundreds of thousands of miles. Expected charge cycles are roughly at around 1000. For EUCs 200 is already an extremely rare occurrence.

 There’s absolutely no point in dancing the steps that will improve the range noticeably after 10000 miles if the wheel will never be ridden more than 5000. Especially when it drastically inhibits the usage of the wheel.

 When you buy a wheel with 1800Wh of battery, you either use the full capacity now which slowly decreases to 80% during the first 10000 miles, or you try to prolong the battery lifetime by voluntarily decreasing your range to 60-80% from day one. It simply doesn’t make any practical sense.

Edited April 14, 2022 by mrelwood

[Richardo]

I want to go off topic here to say i love seeing a discussion(or argument) about what technical tradeoffs are practical in context here in our fun hobby outlet. 
 

I have those same discussions all day at work and i guess I love it. 

[lagger]

2 hours ago, mrelwood said:

… only after well past what anyone has put their EUC through. At the common range of 100-200 cycles the improvement is minute. That makes it detached from the realities of owning and riding an EUC.

Not really, the benefit is there form the start but its not that visible due to scaling. It looks like for the analysis they used some chemistry lasting 2000 cycles but maybe scaling could by applied for our cells. Anyway as I mentioned, one thing is this effect but there are other possibly worse effects for a multi-cell packs. Affecting the life of weakest cells in the pack. Also if you are a not really caring user and sometimes leave your battery at home for days at 0-10% its far worse then when you leave it at 25% but that comes to habits and probability. By these other effects it is possible to kill the battery very soon even faster than in these ideal world charts. When some of the cells get deep discharged by incident.

 

2 hours ago, mrelwood said:

- The battery for an electric car can cost more than $10000.

- An electric car aims for a lifetime of several hundreds of thousands of miles. Expected charge cycles are roughly at around 1000. For EUCs 200 is already an extremely rare occurrence.

Thats true, they also want to have more freedom to choose how much energy is available even if the battery is degrading but its also well known in the industry that deep discharging is not good for battery. EUCs are still not well established and there was a Covid situation where commuting to work wasnt much of an issue. I personally expect more mileage now. At the moment I am at 3000 Km / year. 5000 km / year could be possible when life get back to normal. Then I would degrade the battery in 2-3 years. Yes, thats a v10 but its not really that much km as someone might have thought.

 

2 hours ago, mrelwood said:

 There’s absolutely no point in dancing the steps that will improve the range noticeably after 10000 miles if the wheel will never be ridden more than 5000. Especially when it drastically inhibits the usage of the wheel.

 When you buy a wheel with 1800Wh of battery, you either use the full capacity now which slowly decreases to 80% during the first 10000 miles, or you try to prolong the battery lifetime by voluntarily decreasing your range to 60-80% from day one. It simply doesn’t make any practical sense.

We are in circle here, it comes to who can benefit. Someone with 2000 Wh battery has low benefit but its easier for him to not deep discharge normally. But on the other hand, why I would be deep discharging the pack on daily commuting when I can arrange the charging in such a manner that I will go 85% - 35% keeping the battery happy most of the time while having good performance. Sometimes charging to 100%.

Again, I am not saying its something you should do. I am just saying that its not black and white and certainly it has benefits and some can really benefit and it will cost minimum effort when know what to do.

[mrelwood]

1 hour ago, lagger said:

Also if you are a not really caring user and sometimes leave your battery at home for days at 0-10% its far worse then when you leave it at 25%

Yes, storing the battery empty or full is bad, this was mentioned in the video as well.

1 hour ago, lagger said:

5000 km / year could be possible when life get back to normal. Then I would degrade the battery in 2-3 years.

From what I’ve seen in the forums and our local community, 650Wh wheels like your V10 are really not the ones that people who ride as much as 5000km a year would use. One could say that you might be using your wheel past it’s capabilities. Of course that makes it a very different game, and all tricks you can think of to prolong the battery life become relevant.

 Currently a “normal” capacity for an enthusiastic or a heavy user like you seems to be about three times that of the V10. That also pushes the battery degradation roughly three times further ahead, making it mostly unrelevant.

3 hours ago, lagger said:

and it will cost minimum effort when know what to do.

As I mentioned, I have often squeezed every last bit of range out of my 1500-1600Wh wheels. There is simply no capacity to spare for babying the battery. On the other hand, on packs of this size it is rarely needed.

 

 This discussion with you started from your suggestion that I had missed some extremely important warnings about deep discharging:

23 hours ago, lagger said:

Regarding the tips in the end, I add some more that are missing and extremely important:
One of the biggest thing is not to deep discharge the battery if not necessary (going bellow 30 %)

I’m thankful for the discussion, but I have only learned further confirmations that avoiding deep discharge is as useful as 80% charging, which is practically none at all as long as your battery size even remotely matches your total mileage expectations. A 650Wh wheel is not a 10000 mile (500 charge cycles) wheel without additional care.

[Funky]

All i know it's better to charge to 100% each time. Vs 80% charging.. Because some cells can be more empty. And if you don't charge the wheel to 100% each time, but once per 5/10 time.. Those "lower" cells get more empty. At some point balancing them at those 5/10 times don't fill them completely full anymore. And that's how over time the pack dies.. Because the empty cell gets even more empty. But charging 100% each time, i know the cells are more or less "full", "balanced".

Even when charger turns green.. It's still charging. My charger turns green, but from wall it's still consuming ~50watts. It takes 1-2hours more till my wheel "beeps" that it has finished balancing/charging. In those 1-2hours the charger slowly goes down from those 50watts to 2.5watts. At those 2.5watts it only beeps then. Doh it was green ~2hrs ago..

And i normally charge me wheel when it's at 35-40ish percent. Once/Twice a week..

On paper yes 80% charging sounds awesome - but as we still don't have "smart batteries", where you can see each cell voltage.. It's safer to charge 100% each time.

[lagger]

Cell imbalance doesnt kill your battery pack. Overcharging, deep discharging or overheating cells is what does. Overcharging mostly doesnt happen because of BMS but deep discharge is possible. Its also more probable that you forget your wheel discharged for longer time -> self-discharge -> deep discharge. The imbalance in a fit battery is developing slowly. If your battery pack has significant imbalance after a few cycles it might mean more that the battery is already at the end of life or defective. But yeah, if you are usually utilizing ALL of your battery then its better to have well balanced cells.

So again, the question should be: is it beneficial and should you do it? Are there risks? The question shouldnt be if its good because it is good for battery but you also need to know what you are doing.

The question about benefit / losses is subjective and everyone can have different opinions and usage patterns on their wheels. I do it because V10 lack performance bellow 50% and my usage pattern allows me to charge 90% and discharge to 40% on my daily work commuting.

[Tawpie]

6 minutes ago, lagger said:

my usage pattern allows me to charge 90%

I'm interested in hearing of your long term experience, your pattern is different than the current understanding so having another datapoint to validate or refute the theories is a very good thing indeed!

[supercurio]

2 hours ago, lagger said:

The question about benefit / losses is subjective and everyone can have different opinions and usage patterns on their wheels. I do it because V10 lack performance bellow 50% and my usage pattern allows me to charge 90% and discharge to 40% on my daily work commuting.

Risky move, the V10 uses cheaper, lower capacity Chinese cells in 4p configuration with kind of unknown drain characteristics.
Yet the V10 is a zippy wheel which will peak at 3000W+ in regular city riding acceleration.

I hope that you take care of leaving the wheel on charger for a while at least once a week so the pack has a chance to balance, since there is no doubt the pack will develop imbalance over time.

[0000]

On 4/13/2022 at 10:58 AM, lagger said:

You can normally charge the lithium cells above 5 Celsius but never bellow freezing. Normally people wont have their EUC in these freezing conditions. When coming back from a ride when freezing that doesnt mean the battery is also freezing.

Great points lagger, reading this I just wanted to elaborate a bit on what you said here as I think it'll help explain some of the nuances in this thread with some numbers, even if they are only specifically from the Panasonic NCR18650PD battery cells the researchers used in this study on Aging of Lithium Ion Cells in EVs. While these numbers won't characterize exactly what is going on with our EUC's Samsung 50E, Molicel P42A, or other specific cells with different electrochemical mixtures, the general principles and effects are definitely applicable.

Effect of Battery Temperature while Charging:

You can see in graphs (a) and (b) the noticeable amount of capacity fade divergence of set (1) charged at 0C vs set (2) charged at 25C at only 200 EFC. It was too bad they didn't perform this test up to 500 EFC as the divergence may have been even more pronounced later on if the DCIR started to get exponentially worse in set 1.

Also, these batteries were only charged at a C/4 rate too, at rates greater than C/2 that some charge at, this would likely cause significantly more early capacity fade as the researchers mention in their results summary. Luckily it's easy to control for this factor by charging indoors and not right after a ride in cold weather. Another cool thing this study details is the protective effect of regenerative braking has on the capacity fade phenomenon.

Effect of Battery Temperature and Regenerative Braking while Charging:

Boxing out the most EUC relevant set of tests, here we can see that at every temperature range tested, regenerative braking has not only a protective effect against capacity fade (and more regen = more better), but lower temperature during discharge/use has much less effect on the cumulative capacity degradation of these cells. It looks like less than 2% between 40C and 10C after 500 EFCs.

In other words, its good to know battery warmers generally aren't really needed or worth it if we can assume this behavior also applies to our specific EUC cells.

So now that I've had more time to parse this study, I also wanted to highlight the effect on both State of Charge and Depth of Discharge since I got into a discussion about this with @mrelwood on another thread earlier and I see it's being discussed here too.

Effect of SoC and DoD on Capacity Degradation:

First, I would point out that most of our EUCs have a Low Voltage Cutoff programmed between 3.2V and 3.3V, so the 3.2V as a worst-case scenario is the most applicable to us.

So after 500 EFCs, the difference between a 4.2V-3.2V set and a 4.1V-3.2V set is only 1.2% capacity fade, a pretty remarkable result. I think that really nails home the SoC point that @mrelwood has been arguing here and elsewhere. Charging to full or very near full for minor regen braking protection fresh off the charge makes the most sense, with a few caveats.

The small difference they show between 4.2V and 4.1V SoC is both temperature and C-rate dependent as I think the researchers were charging at C/4 for this test as well. Lower charge temps, higher C-rates, and electrochemical differences between your specific cell may increase the capacity fade amount to make lower SoC "worth it" IF your battery balancing method can accommodate it safely.

Second, discharging to 2.5V is really not great for capacity fade. Luckily we don't have to worry about this at all.

In fact, at the 3.2 LVC that the majority of EUCs are programmed with (or above), changing the DoD to 3.4V only preserves an extra 0.8% capacity after 500 EFCs under these controlled conditions. Considering that few if any EUC riders are consistently hitting riding out their LVC to shut-off every cycle, the capacity fade won't likely be as bad as tests like this indicate. In other words, you got nothing to worry about with normal use unless you are trying to make your wheel's battery packs last 1000 EFCs or more.

Edited April 22, 2022 by Vanturion

[Tawpie]

38 minutes ago, Vanturion said:

you are trying to make your wheel's battery packs last 1000 EFCs or more

let's see, back of the napkin... 2000 miles per year. 60 miles per EFC. Drat. I don't absolutely have to find a replacement for the 16X for 30 years. I sure hope my S22 arrives before then.

[0000]

11 minutes ago, Tawpie said:

let's see, back of the napkin... 2000 miles per year. 60 miles per EFC. Drat. I don't absolutely have to find a replacement for the 16X for 30 years. I sure hope my S22 arrives before then.

In all seriousness, for the one-and-done EUC lifers, there's also the battery Calendar Aging effect to consider which wasn't discussed, but is also characterized in the study too. That effect is combated by storing your wheel at low SoC for any long period of time as well as at lower temps.

So basically, put your battery-empty EUC in the freezer over winter, and thaw in spring before eating charging.

[Begodecrashtestdummy]

19 minutes ago, Vanturion said:

In all seriousness, for the one-and-done EUC lifers, there's also the battery Calendar Aging effect to consider which wasn't discussed, but is also characterized in the study too. That effect is combated by storing your wheel at low SoC for any long period of time as well as at lower temps.

So basically, put your battery-empty EUC in the freezer over winter, and thaw in spring before eating charging.

What is the best way to store a wheel if you have to go away for 9-18 months maybe less with good behavior 🤣🤣🤣 asking for a “friend” 😉 the wheel is brand new should I just leave my wheel in the box …I just ordered it two days ago 

Edited April 22, 2022 by Dosingpsychedelics
🚔 “failure to comply with police signal” (F3) 😝