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WTB First EUC (v8, ks16s) US

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3 hours ago, mrelwood said:

To be precise, balancing only happens at the very last stage of charging. If you always stop the charging at 90% or below, balancing will never happen and the cell voltages will drift being further unbalanced.

To balance a battery pack that doesn’t charge to 100%, one should have it plugged in the charger at 90-100% charge for as much as possible. Fe charge to full, ride a few miles only, charge to full, and repeat.

I thought that if you have x amount of cells that no longer can reach 4.2V, you would “balance” the pack by not charging to 100%, aka charging to a level all cells can reach, because I didn’t think the BMS in an EUC was advanced enough to either set a new reduced average top end voltage level or “manage” the damaged cells after a 100%-0%-100% charge-discharge-charge cycle. It would be awesome to be wrong about this.

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47 minutes ago, Espen R said:

I thought that if you have x amount of cells that no longer can reach 4.2V, you would “balance” the pack by not charging to 100%, aka charging to a level all cells can reach

Quite the opposite. A parallel set of cells would kind of work that way, but since the battery pack has the cell (pairs) in series, the charging current goes through every cell, and they just store as much of that energy as they can. The charger voltage indeed limits only the overall (or average) voltage.

The cell pairs that are hardwired in parallel are of course in the same voltage all the time.

If the BMS didn’t balance or cut off charge, when the overall charge of the pack reaches 67.2V, some of the cell pairs would be lower than 4.2V and some would be higher. A series set of cells can’t balance themselves in any way. Quite the opposite actually, as when stressing the pack the worst cells are relatively stressed the most, so they get even more out of balance.

47 minutes ago, Espen R said:

 because I didn’t think the BMS in an EUC was advanced enough to either set a new reduced average top end voltage level or “manage” the damaged cells

What the BMS does is it monitors each (parallel pair of) cells, and if any of them reaches 4.25-4.30V, it cuts of the charging completely. That does set a new reduced average maximum charge, since the weaker cells are still at a lower voltage.

What the BMS also does is give a bit more charge to the weakest cells, but only when at somewhere around 90-100% of max charge. So it also does manage the cells that are weaker. And this is the mechanism that can be used to revive a pack that is going out of balance. Until the BMS cuts off the charge of course.

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10 minutes ago, mrelwood said:

Quite the opposite. A parallel set of cells would kind of work that way, but since the battery pack has the cell (pairs) in series, the charging current goes through every cell, and they just store as much of that energy as they can. The charger voltage indeed limits only the overall (or average) voltage.

That explains a lot. I used to vape, so my main experience with Li-ions are 2/3 cells in a serial configuration, 2 cells in parallel or single cells. The “BMS” in most of the mod's I used were so poor that charging the batteries in a serial configured mod ran the risk of overcharging one of the cells to the point of rapid degradation or even ventilating, so I only used an external charger.

 

28 minutes ago, mrelwood said:

What the BMS does is it monitors each (parallel pair of) cells, and if any of them reaches 4.25-4.30V, it cuts of the charging completely. That does set a new reduced average maximum charge, since the weaker cells are still at a lower voltage.

What the BMS also does is give a bit more charge to the weakest cells, but only when at somewhere around 90-100% of max charge. So it also does manage the cells that are weaker. And this is the mechanism that can be used to revive a pack that is going out of balance. Until the BMS cuts off the charge of course.

 That is such a relief. Huge thank you for curing my BMS ignorance! Because of my more intime battery experience and a (unfounded) general BMS distrust, I have always assumed that a 100% charge ran the risk of overcharging some of the serial connected parallel pairs, because I couldn't imagine that a EUC BMS would monitor every parallel pair. I have never charged my wheels to 100%, usually 80%, my 18XL have been charged to 90% one time. Would it be smart to do a 100% charge a couple of times a year to allow the BMS to do it's magic?

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1 hour ago, Espen R said:

Would it be smart to do a 100% charge a couple of times a year to allow the BMS to do it's magic?

Usual recommendation is full charge to 100% + 3-5hrs on the charger after the charger LED has turned green, but severe cases will take dozens of hours of balancing alone. Also, since actual cell degradation due to charging to 100% will only cause trouble after 10 000 miles at the earliest while unbalanced cells can ruin the battery in six months, I would always prioritize having the pack as balanced as possible over other battery concerns.

Since your cells are most probably quite off by now, it is unlikely for them to reach 100% right away. I’d cycle between 90-100% until it reaches 84V.

Monitor the voltage from an app while charging. When the voltage starts to fall you’ll know that the BMS has cut off the charge.

I only worry about charging to 100% if my wheel won’t be ridden in a week or more.

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13 minutes ago, mrelwood said:

Usual recommendation is full charge to 100% + 3-5hrs on the charger after the charger LED has turned green, but severe cases will take dozens of hours of balancing alone. Also, since actual cell degradation due to charging to 100% will only cause trouble after 10 000 miles at the earliest while unbalanced cells can ruin the battery in six months, I would always prioritize having the pack as balanced as possible over other battery concerns.

Since your cells are most probably quite off by now, it is unlikely for them to reach 100% right away. I’d cycle between 90-100% until it reaches 84V.

Monitor the voltage from an app while charging. When the voltage starts to fall you’ll know that the BMS has cut off the charge.

I only worry about charging to 100% if my wheel won’t be ridden in a week or more.

With my electric fat-bike I didn’t bother to buy a smart charger, but I usually didn’t charge it until I knew I would use it that day. After a about year I started to run out of juice on the 44 km on/off-road route I only rode during the summer months, even though I had reduced the level of assistance from what I used last year, and by the end of summer I had do reduce the distance. Without at least some assistance, a fat-bike isn’t within my physical ability to operate, at least not on the hilly off-road parts. It was pretty clear that the bikes battery pack had lost at least 15% of its capacity. I sold the bike last spring and bought the V10F with a smart charger;)

The 18XL is on a 100% charge now:) After seeing first-hand the degradation that could happen to single cells and a bikes battery pack that is charged to 100% and because of the general advice given in the “Li-ion world” and by the automotive industry in regards to electric cars, I think I'll stick to my 80% charging routine, but now with an added occasional 100% charge.

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@mrelwood I Did a 100% charge, or I stopped it when the wheel showed 84.2V when I turned it on, because I was afraid to overcharge the battery pack. Then I went for a ride, in the worst rainfall so far this year, because I didn’t want it to sit with a 100% charge. So, I conclude that the 80% charging routine doesn't unbalance the pack, and that after 1.5 years and 3600 something km (2250+miles) the battery pack is still as good as new.

Really impressed by the smart charger, well not so impressed that it charged to 84.2V and kept on going (or is it supposed to do that?), but it charged really slow the last stretch (at 83.7V it was down to about 30W), which is a good thing for Li-ions.

Screenshot_20200209_154811_com.kingsong.dlc.jpg

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Hey guys! @mrelwood @Espen he charged it over night and said it charged to 100% 😀

He also sent me a diagnostic report showing it, so I think I'm going to follow through with the purchase! 💙

 

Thank you again for all your help! 

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Nice! 450 is a good price if everything is ok. Enjoy!

Ocasionally charging to 100% and keeping the charger in for a few hours/overnight will balance the cells. This helps with battery longevity.

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11 hours ago, mrelwood said:

It’s true that sitting at 100% is harmful for the battery in the long term. I don’t know what the ”long term” means precisely, but in my understanding a few days wouldn’t make a notable difference. Waiting 4 months for the winter to pass would.

What’s your sources on this? I couldn’t find anyone recommending leaving a 100% charged battery for a few days. Tesla only recommends 100% charge if you really need the range, and they use the term “immediate use” when the car is fully charged. I also read that only a few degrees increase in room temperature can be very harmful for a 100% charged battery.

I had on average 5 vaping mods in daily use, and I always had two sets of batteries for every mod, so that I could switch to fully charged batteries right away, and I immediately charged the batteries I took out. This meant that every set would sit fully charged for about 2-3 days. I probably went through something like 60-100 batteries in the years I vaped, and I only had 4 batteries that lasted longer than 2 years (Sony VTC5). A few lasted less than a year, but the vast majority lasted about 2 years before they were below 70% of their capacity, and not usable to me. I only used 20 – 30A Sony, Samsung and LG’s. PS: I also almost never went below 30-50% before I charged them.

My fat-bike’s battery pack would also only have lasted about 2 years (at least 15% degradation after 1 year) before it would be below 70% of its capacity, and it only sat at 100% for a few days on rare occasions, it was mostly used within the same day after a full charge.

There are quite a few 2012 Tesla Model S with high mileage (+-257 000km/160 000miles), that have less than 10% battery degradation. Following Tesla’s charge guidelines seems to be a good choice.  

I’ll follow your excellent advice on allowing the BMS to balance the pack with an occasional 100% charge, but I’ll stick to limiting the majority of my charging to 80%-90%:)

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6 minutes ago, Espen R said:

What’s your sources on this?

The source for ”in my understanding” is quite a lengthy and an irrelevant topic, no point going there. I haven’t seen, read or heard of any specific amount of time that a li-ion battery should or shouldn’t be kept at full charge. It’s not what I said or implied, don’t try to pick a fight.

I have vaped for over 10 years now, and since the VTC6 was released many years ago, I’ve swapped between two of them, and the other always remains trickled in the charger, around the clock, until the other is empty. I vape constantly, yet I haven’t noticed any degrading on either of these cells.

There are several reasons why us discussing this for any length of time will never bring anything worthwhile to the table:

- No amount of personal experience translates to universal guidelines.

- No amount of other person’s experiences will trump one’s own.

- EUCs, and especially their chargers, BMSs, and battery handling mechanisms are not Tesla cars. They are not vaping devices or RC helicopters either.

- 0% of electronic devices run on percents. Percentage is a 100% relative unit, and it’s 100% up to the author to decide what the scale is.

 

A two course meal for thought though: Do you keep your laptop computer plugged in? And how do (or would) you manage the battery on a cordless drill?

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1 hour ago, mrelwood said:

The source for ”in my understanding” is quite a lengthy and an irrelevant topic, no point going there. I haven’t seen, read or heard of any specific amount of time that a li-ion battery should or shouldn’t be kept at full charge. It’s not what I said or implied, don’t try to pick a fight.

I don’t understand why you would think I’m trying to pick a fight, but I’m truly sorry if it came across that way. The reason I asked about your sources for your claim that: “a few days (at 100%) wouldn’t make a notable difference”, is because I genuinely wanted to know. The consensus of all the research and general guidelines I have read on the subject have been clear about not leaving a fully charged battery for any amount of time. My goal is to learn as much as I need to extend the life of my battery packs for as long as possible, so if you had other sources on this than what I have come across, I would really have liked to read them, I mean you have already enlighten me on the BMS, which I really appreciated, so I asked you about your sources regarding you as an authority on the subject.  

1 hour ago, mrelwood said:

I have vaped for over 10 years now, and since the VTC6 was released many years ago, I’ve swapped between two of them, and the other always remains trickled in the charger, around the clock, until the other is empty. I vape constantly, yet I haven’t noticed any degrading on either of these cells.

Hold on to those batteries, because they must be from a golden batch. What is the resistance of your coils and at what wattage are you vaping?

I vaped for 9 years, and in 7 of those years I mainly vaped coils with fairly low ohms, between 0.15-0.2 ohms, mostly 20 or 22 AWG single coils at 45-80W, so my batteries had to work relatively hard. For my first 2 years of vaping I mainly used Kayfun’s at 12-18W, and the 4 VTC5’s that survived for more than 2 years, started their life in that era.

1 hour ago, mrelwood said:

There are several reasons why us discussing this for any length of time will never bring anything worthwhile to the table:

- No amount of personal experience translates to universal guidelines.

No, but there are universal guidelines out there based on research. All the tests and research I've read on cycles of 100% charging is pretty consistent. 300-1000 cycles before they are degraded to below 70% of their capacity, which for moderate to high use will indicate a lifespan of about 2-3 years, and since that is pretty much the same as my own experience, I thought I’d use my vape batteries and my e-bike as an example. When it comes to charging cycles that are kept between 20-80% of the battery's capacity, I’ve seen that they have achieved up to 16 000 cycles. EUC battery packs are quite expensive, so I want mine to last longer than 2-3 years.

 

1 hour ago, mrelwood said:

- EUCs, and especially their chargers, BMSs, and battery handling mechanisms are not Tesla cars. They are not vaping devices or RC helicopters either.

No, they are not, but they all use Li-ions (apart from RC’s that mainly use Li-po batteries) and they are all bound to the same restrictions and capabilities of the battery chemistry, so the guidelines regarding charging and storing above 90% of true capacity does apply to all Li-ion devices.  

 

2 hours ago, mrelwood said:

- 0% of electronic devices run on percents. Percentage is a 100% relative unit, and it’s 100% up to the author to decide what the scale is.

Yes, they are correctly measured in volt. I do know that for some devices a 100% charge would actually only be something like 95%, because the charger is set to stop at a lower voltage to reduce harm on the battery. But for most devices a 100% charge would still be above 90% of the actual max voltage, so you are still within the threshold of causing harm to the battery, therefore I think it is still relevant to use the terms 100% or fully charged.

 

2 hours ago, mrelwood said:

A two course meal for thought though: Do you keep your laptop computer plugged in? And how do (or would) you manage the battery on a cordless drill?

I don't have a laptop now, but when I did, many years ago, I was advised to take the battery out when it was plugged in, but then I didn’t know why, so I didn’t really follow that advise. Don’t know exactly when the battery died, because it was a power thirsty gaming laptop that I kept plugged in, but after about 4 years I discovered that the battery was dead. We plan to buy a laptop this spring, but now, even with my "new" knowledge, I’ll probably take a gamble and keep the battery in. They are cheaper to replace now, and I do hope the manufactures have learned to stop the charging before the battery packs reaches the actual 100%.

As for my cordless drill batteries, I started with only charging them when I intended to use them, but now my girlfriend is the main user at her shop, so I don’t know what she does. They are fairly inexpensive to replace, so I don’t really care.

 

My intentions, as I wrote, has not been to fight about this, I didn’t feel like this was a “you vs me battle”, but I'm really sorry if you felt it was. I thought we were exchanging our knowledge and experiences to enlighten the subject. I really just want learn and share my 2 cents of knowledge. When it comes to charging and taking care of a battery pack, I’ve done a fair amount of research about what happens to a cell or battery pack when it is charged above 90% of its true capacity, but I’ve done very little reading on battery management systems, so I thought our combined knowledge on this subject would be interesting for others to read. I was genuinely glad when you corrected me and shared your knowledge about BMS’s, because now I can take even better care of my battery packs.  

 

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17 hours ago, mrelwood said:

It’s true that sitting at 100% is harmful for the battery in the long term. I don’t know what the ”long term” means precisely, but in my understanding a few days wouldn’t make a notable difference. Waiting 4 months for the winter to pass would.

´

 

6 hours ago, Espen R said:

What’s your sources on this? I couldn’t find anyone recommending leaving a 100% charged battery for a few days. Tesla only recommends 100% charge if you really need the range, and they use the term “immediate use” when the car is fully charged. I also read that only a few degrees increase in room temperature can be very harmful for a 100% charged battery.

 

6 hours ago, mrelwood said:

The source for ”in my understanding” is quite a lengthy and an irrelevant topic, no point going there. I haven’t seen, read or heard of any specific amount of time that a li-ion battery should or shouldn’t be kept at full charge. It’s not what I said or implied, don’t try to pick a fight.

 

1 hour ago, Espen R said:

 The reason I asked about your sources for your claim that: “a few days (at 100%) wouldn’t make a notable difference”, is because I genuinely wanted to know.

:D There is no claim, recommendation or whatsoever from @mrelwood's side - he is just stating that he does not know how bad it is to leave the batteries for some "not too long time". 

All what i have read (and wrote) about this here, was from https://batteryuniversity.com/learn/article/how_to_store_batteries their table of how much LiIon batteries loose when stored at different temperatures, soc for about a year...

So undoubtly, also from many other articles, keeping LiIon at 100% is not good for them. For the EUC battery packs we have to charge them to 100% and keep them there for some hours, so the BMS can balance.

But afair there was never anything mentioned about any studies, articles or whatsoever of the effect of "short/medium time full charge" on a Li Ion (at "normal" temperatures...)

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4 hours ago, Espen R said:

I don’t understand why you would think I’m trying to pick a fight, but I’m truly sorry if it came across that way.

It was your enthusiasm in grabbing a scentence I thought I clearly enough preceeded with ”I don’t know but in my understanding...”.

When the harm of 100% storage was discussed some time last year, we did realize what @Chriull mentioned as well, that the only data we can find about the measured damage is indeed over a full year at 100%. It was then concluded that a few days don’t seem to matter much at all for our use.

And even your laptop’s battery seems to have taken a few years to die when being kept at 100% without perhaps a single charge cycle.

4 hours ago, Espen R said:

What is the resistance of your coils and at what wattage are you vaping?

30-40W on regulated mods.

4 hours ago, Espen R said:

300-1000 cycles before they are degraded to below 70% of their capacity, which for moderate to high use will indicate a lifespan of about 2-3 years

The main reason I don’t worry about a week at 100% is that I believe your math above to be incorrect. A full charge cycle is not down to EUC 0%, but the rated minimum voltage of the cell, which IIRC is usually 2.5V. So if I get 65km of range on a 1600Wh MSX (down to 3.35V, or 4%), a full charge cycle is roughly worth 130km. 300 charge cycles equals 39 000 km, or over 25 000 miles. And that is the worst case scenario. And would take even me a whole lot longer than 2-3 years.

I have zero intention to ride any unicycle that far, and I have yet to hear a single person in the world to have even done that.

But if you search for charging issues on this forum, you can pretty easily find dozens of cases where the battery doesn’t charge to 100%, or has suddenly cut off at a low charge, wheels losing their range or sense of power, etc.

From the above it seems quite clear that storing at 100% is very unlikely to have yet caused any issues to a single EUC rider, while other battery issues are quite common. That is why avoiding the 100% is very low on my priority list.

And for the same reason my guess is that your fatbike’s battery died from other causes as well. I don’t know if it even has a mechanism for balancing the cells, so unbalanced cells would be my first guess, as it seems to clearly be the most common issue on EUCs, despite every EUC having a clever balancing mechanism. (Lack of documentation and the charger led turning green distractingly early are probably the main reasons. Aren’t they why we are having this discussion right now as well?)

 

(Ps. Unplugging the laptop charger even just once a month and letting the battery run almost empty is already supposed to help a lot in making the battery last much longer.)

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17 hours ago, mrelwood said:

It was your enthusiasm in grabbing a scentence I thought I clearly enough preceeded with ”I don’t know but in my understanding...”.

When the harm of 100% storage was discussed some time last year, we did realize what @Chriull mentioned as well, that the only data we can find about the measured damage is indeed over a full year at 100%. It was then concluded that a few days don’t seem to matter much at all for our use.

And even your laptop’s battery seems to have taken a few years to die when being kept at 100% without perhaps a single charge cycle.

30-40W on regulated mods.

The main reason I don’t worry about a week at 100% is that I believe your math above to be incorrect. A full charge cycle is not down to EUC 0%, but the rated minimum voltage of the cell, which IIRC is usually 2.5V. So if I get 65km of range on a 1600Wh MSX (down to 3.35V, or 4%), a full charge cycle is roughly worth 130km. 300 charge cycles equals 39 000 km, or over 25 000 miles. And that is the worst case scenario. And would take even me a whole lot longer than 2-3 years.

I have zero intention to ride any unicycle that far, and I have yet to hear a single person in the world to have even done that.

But if you search for charging issues on this forum, you can pretty easily find dozens of cases where the battery doesn’t charge to 100%, or has suddenly cut off at a low charge, wheels losing their range or sense of power, etc.

From the above it seems quite clear that storing at 100% is very unlikely to have yet caused any issues to a single EUC rider, while other battery issues are quite common. That is why avoiding the 100% is very low on my priority list.

And for the same reason my guess is that your fatbike’s battery died from other causes as well. I don’t know if it even has a mechanism for balancing the cells, so unbalanced cells would be my first guess, as it seems to clearly be the most common issue on EUCs, despite every EUC having a clever balancing mechanism. (Lack of documentation and the charger led turning green distractingly early are probably the main reasons. Aren’t they why we are having this discussion right now as well?)

 

(Ps. Unplugging the laptop charger even just once a month and letting the battery run almost empty is already supposed to help a lot in making the battery last much longer.)

I have been wondering why we conclude so differently from reading what I assume are the same sources, so I tried to break down my line of thought.

When I read the single cell tests, I see them as a test of 1st bin batteries. I then assume that the batteries we have in our EUC’s are not 1st bin. I hope we at least have 2nd bin, but we might have 3rd bin batteries. I then add my personal experience with individual cells and calculate that an X-amount (I will get back to the number) of the batteries in our EUC battery packs are weak cells, and that they will not handle the same amount of stress, 100% charging and high drain discharging, as the majority of cells. With your information on how the BMS would handle these weak cell pairs and rebalance the battery pack, I now see that this isn’t as bad as I initially thought, but I still believe that an 40-80% charge cycle will help to prevent these week cells from going bad in the first place.

So, when I read 3-500 charge cycles of 1st bin batteries, I do know that this is a 0-100% cycle, but here I calculate in the X-amount of week cells in the battery pack and estimate that a 40-100% cycle with 2nd or 3rd bin batteries would create a very similar result because of the amount of potential week cells going bad in the battery pack. My experience from my vape batteries are pretty much bang on a 300 cycle with a 50-100% charge. I forgot about my mech-mod faze, where I went through 20-30 batteries in a year, so my estimate of 60-100 batteries in 9 years is a bit low. It’s more likely 80-120 batteries. I usually bought my batteries from serious vendors, so I guess I mainly got 2nd bin batteries.

Another thing I calculate in as a stress factor is all the different temperatures I expose my wheel to, -20c - +35c, and since we don’t have active cooling/heating in our battery packs, I believe this also contributes to battery degradation or stress to the weak cells. I’m 189cm tall and weigh 110 kg, which is about 10-15 kg more than my optimal weight, so the amount of high drain stress I put on my battery pack because of my weight, is also calculated in as a source of degradation/stress.

When I read about storing a battery at 100% and how different temperatures can affect them, I calculate that the weak cells will have problems handling even small temperature changes.

Regenerative breaking and the risk for overcharging is also something I’ve given some thought to, when it comes to charging to 100%. My Onewheel gave me a warning via the app, but unfortunately this warning came at about the same time as the cut off, and since we lived on the top of a hill, I took a few nasty falls before I learned to ride bit on our lawn before I went down the hill. I was glad the OW had an overcharge protection feature, just whished it could be implemented a bit safer for the rider:) How does a EUC handle regenerative breaking when it is fully charged?

I really whish there was more research on cheap-ish battery packs without active cooling/heating, so that I didn’t have to do all these guesstimations.

The conclusion to the tests, research, general guidelines and my experiences together with my assumptions, guesstimations and calculations, are very clearly in favour of reducing the only stress factor I can do something about, which is limiting the level of charge. I assume the cause of imbalance in a battery pack is cell pairs going bad, so my strategy is to try and limit this amount by doing the majority of charging within a 40-80% charge cycle.

The reason we conclude differently, might be because of the value we put in the X-amount of potential bad/weak cells in our battery packs. I might be overconcerned or you might be overconfident, who knows?

I am from the northern parts of Norway, and we are known for being overconfident in our own reasoning, I used to drive my teachers and professors mad (but I did get good grades). I do have the impression that people from the north of Norway have very much in common with people from Finland when it comes to having a slightly stubborn overconfident way of reasoning, so I doubt we’ll ever agree and reach the same conclusions, but I have very much appreciated this and feel like I’ve learned a lot, so thank you for taking your time to do this:)   

Edited by Espen R

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The reason that differing views and understandings can form in the first place is the lack of precise and consistent information. In our time this is what bugs me about batteries; how is it possible that every single aspect of their degradation and handling is not widely known, written in Wikipedia in minute detail, etc?

I guess there are just so many variables that universal guidelines wouldn’t be all that universal after all.

My father worked his whole working life with car batteries. When he gave me his old grass cutter, he emphasized how important it is that the (Li-ion) batteries are charged to full immediately after use. Well, as a vaper and EUC enthusiast I of course knew his career-influenced advice was incorrect, to which he replied that this method has at least kept the batteries in tip top shape for several years already.

Now, I don’t know if the batteries really are in good condition or not, but if they are, I know them to be so for other reasons than his charging habits. Good luck making him see that though...

Reason I told this was to point back to what I wrote earlier: No amount of personal experience equals universal knowledge, and no amount of other person’s experience can sway one’s own.

Now, everyone reading this knows that my father handled the batteries badly, so my guess is that there is a built-in battery management that prevents this from being harmful. Maybe they are never even charged above 4.0V. Or, the batteries might actually be in a crappy condition, I really don’t know. In any case the reason is different than what my dad thinks it is.

 

@Espen R, I’m sorry that I misinterpreted your interest in the subject as trying to pick a fight. I thought I was facing just a strict ”no amount of other person’s experience...” attitude. I’m glad that I was wrong, since I enjoy this discussion quite a bit! Your attitude towards this discussion is actually quite admirable.

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I have been wondering why we conclude so differently from reading what I assume are the same sources

If one of your sources as well is this very forum, it’s one huge source, and I can easily see how differing opinions can form.

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I still believe that an 40-80% charge cycle will help to prevent these week cells from going bad in the first place.

We naturally seem to agree which circumstances and handling behaviour are bad for the cells, but I don’t think there is a way for us to come up with a founded answer to a very precise ”which is worse?” question, let alone ”how much worse?”. So by belief we must indeed act on by.

 

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but here I calculate in the X-amount of week cells in the battery pack and estimate that...

I agree on weak cells, ie. an unbalanced pack being the cause of an early battery death, instead of even aging of all cells. Which again raises the importance of repeated balancing.

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My experience from my vape batteries are pretty much bang on a 300 cycle with a 50-100% charge.

That makes it 150 full charge cycles. That would still equal a minimum riding range of about 20 000 km.

Do I read you correctly that you disagree with the estimation of 150/300 full charge cycles resulting in a minimum riding range of almost 20 000 / 40 000 km? 

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I forgot about my mech-mod faze, where I went through 20-30 batteries in a year

This is impossible for me to grasp. That would average a 150-cycle cell lifetime of 2 weeks, and a constant rate of 2hrs or less to go through a full charge cycle. Even charging at 750mA takes 3 hours to fully charge a 2200mAh battery. I vape constantly, at 30-40W, and it takes me perhaps 12 waking hours to go through a full cycle on a single cell. The average cell capacity hasn’t gone up more than perhaps 50% in 10 years. What am I missing?

 

A crucial difference with vaping is that when a single cell no longer provides the wanted vaping power, it has indeed aged (prematurely or otherwise). When an EUC battery pack no longer provides the wanted range and power, it doesn’t necessarily or even usually  have a single aged cell in it yet. One cell can just have originally had a slightly higher internal resistance, lower capacity or different State Of Charge, which has over time caused it to be constantly at a lower SOC than the rest. Which will then stress this one cell more than the rest, accelerating the voltage imbalance further already much before the cell or it’s capacity has noticeably aged. The balancing current the EUC BMS provides is very small, and once the voltage span of the cells is something like 0.2V, it might already be too late to be remedied by BMS balancing.

This is why I think that if you are worried about your battery cells aging (due to being charged to 100%), you should worry many times as much about the cells being even slightly unbalanced. Everything I have experienced and read about EUC packs dying points to cell imbalance being the cause.

 

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Regenerative breaking and the risk for overcharging is also something I’ve given some thought to, when it comes to charging to 100%.

If one lives on top of a hill, one really should worry about that! I have had my 16S warn me about overvoltage a few times when braking a bit stronger from 30 to 10 km/h on flat ground, about 300m after starting my regular trip.

I don’t remember what the overvoltage warning or cut-off limits are on any EUC, but if the wheel has such a warning, just easing up on brakes will stop the overvoltage in a second. (Being stored at 100% takes about a year to kill the battery...) Going downhill one of course doesn’t have that option. One forum member was worried that due to living on top of a hill and charging to 80-90% he couldn’t balance the cells often enough!

Although, if the battery is unbalanced, the BMS may have stopped the charge when a single cell is already at 4.25-4.28V. Then the cut-off limit and even venting is much closer, since the pack doesn’t report the voltage of the highest cell to the main board. The board just measures if the total voltage is above the set limit and warns based on that.

Yet another reason to aim for a perfect cell balance!

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in favour of reducing the only stress factor I can do something about, which is limiting the level of charge.

That’s not correct! The voltage balance of the cells is something only you can do something about! And I now believe it is something you can do much more about than premature aging of cells.

I actually had pretty much identical view to yours 2.5 years ago when I started using the Charge Doctor and hadn’t read on failing batteries on our forum. Or having had battery failures myself.

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I assume the cause of imbalance in a battery pack is cell pairs going bad

As I wrote above, the cells don’t need to have gone bad for the pack to be unbalanced. The cells by their fundamental nature have slight variations in capacity, resistance, and even initial state of charge. If there is nothing to control the imbalance, the voltage difference can get too high way before the cells have aged one bit.

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The reason we conclude differently, might be because of the value we put in the X-amount of potential bad/weak cells in our battery packs. I might be overconcerned or you might be overconfident, who knows?

The weak cells are a sure cause for an unbalanced pack, so the only thing I’m confident is that the probability of weak cells in a 64-140 cell pack is extremely high. The weak cells are why balancing is so important. And they are why I had to first replace cells in my 16S at 4000km despite having been balancing more than recommended already back then.

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I doubt we’ll ever agree and reach the same conclusions, but I have very much appreciated this and feel like I’ve learned a lot, so thank you for taking your time to do this:)   

I don’t expect to change anyone’s mind (or to have my mind changed) at a discussion forum, so I’m cool with just having the opportunity to say what I’ve read, experienced and learned, and what is my take on it all. I’m sorry I don’t know how to do it with fewer words though! Every reader has to weigh how my (or anyone’s) posts resonate, and decide wether or not to have them included in conforming their personal viewpoints.

Thank you for being a part of this amazing forum! :thumbup:

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10 hours ago, mrelwood said:

I agree on weak cells, ie. an unbalanced pack being the cause of an early battery death, instead of even aging of all cells. Which again raises the importance of repeated balancing.

That makes it 150 full charge cycles. That would still equal a minimum riding range of about 20 000 km.

Do I read you correctly that you disagree with the estimation of 150/300 full charge cycles resulting in a minimum riding range of almost 20 000 / 40 000 km?

I don’t see how 300 half cycles (150 full cycles) would give me 20 000 – 40 000 km. If I mainly rode on flat tarmac in the summer, then perhaps yes. From April – October my “daily” (3-5 days a week) 18-22 km hilly off-road/gravel/tarmac rides eats range like a mf. In the winter I ride different slightly shorter and less frequent routes, but then the temperature can cut the range by quite a bit. In-between all this I run errands and I do grocery shopping (about a 50/50 split between the 18XL and the V10F), and my girlfriend and I often take long weekend rides. So, I would estimate that 300 cycles, or more precise 300 50-100% charges, would get me about 14 000 – 18 000 km before I would reach the point where the battery pack theoretically could be around the dreaded 70% capacity left mark, which still sounds a lot, but what I worry about could already begin at the half way point. At 7000 – 9000 km, with a possible 15% degradation, I fear that voltage drops and imbalance issues could start to occur, and that I no longer can do the hard rides I do today. If I stay healthy and injure free for the next 10 months, I’ll have something like 6500 – 7500 km on the 18XL by the end of the year.
11 hours ago, mrelwood said:

The reason that differing views and understandings can form in the first place is the lack of precise and consistent information. In our time this is what bugs me about batteries; how is it possible that every single aspect of their degradation and handling is not widely known, written in Wikipedia in minute detail, etc?

I guess there are just so many variables that universal guidelines wouldn’t be all that universal after all.

Totally agree, it is really frustrating not having any definitive answers, but I kind of enjoy it. The reason I enjoy my layman obsession of science (mainly physics) and philosophy so much, isn’t because it provides answers or absolute certainties, it is the open-minded never-ending process of questions leading to even more questions and so on. Socrates said: The only true wisdom consists in knowing that you know nothing, and that still holds water today:)

But, if I, with a 40-80% charging routine sprinkled with an occasional 95-100% balance charge, manage to get to 6500 – 7500 km on my 18XL with a fully balanced battery pack with little to no capacity loss by the end of this year, then it would at least be an indication that reducing the amount of 100% charge stress can prevent weak batteries from going bad. Still not clear evidence though, but at least an indication.

Would the BMS be able to balance the battery pack with a 95% charge? The end of the year result on my wheel would be even more interesting if I didn’t do any 100% charges, apart from the one I just did.

11 hours ago, mrelwood said:

As I wrote above, the cells don’t need to have gone bad for the pack to be unbalanced. The cells by their fundamental nature have slight variations in capacity, resistance, and even initial state of charge. If there is nothing to control the imbalance, the voltage difference can get too high way before the cells have aged one bit.

The difference here is just how we use the term bad. By bad cells I meant cells not preforming as the should do, not totally broken. “Bad” milk can still be used in waffles, “bad” cells can still function, but not optimally:) Still believe that provoking the weak cells with a 100% charge has a higher potential of causing imbalance issues than what a 40-80% charge routine does, but by the end of this year we’ll see how my 18XL battery pack is doing. After 3600+ km, I have no balance issues or capacity loss. This isn't remotly enough to call it an indication that my theory holds water, at best it could be called a trend, which in science terms means: we don’t know anything yet, but…. 

11 hours ago, mrelwood said:

I don’t expect to change anyone’s mind (or to have my mind changed) at a discussion forum, so I’m cool with just having the opportunity to say what I’ve read, experienced and learned, and what is my take on it all. I’m sorry I don’t know how to do it with fewer words though! Every reader has to weigh how my (or anyone’s) posts resonate, and decide wether or not to have them included in conforming their personal viewpoints.

Thank you for being a part of this amazing forum! 

Ditto:)

12 hours ago, mrelwood said:

This is impossible for me to grasp. That would average a 150-cycle cell lifetime of 2 weeks, and a constant rate of 2hrs or less to go through a full charge cycle. Even charging at 750mA takes 3 hours to fully charge a 2200mAh battery. I vape constantly, at 30-40W, and it takes me perhaps 12 waking hours to go through a full cycle on a single cell. The average cell capacity hasn’t gone up more than perhaps 50% in 10 years. What am I missing?

I think both of my 4 port chargers I had then could do 1000mA on all ports and 1500mA if I only used 2 ports and 2000mA on 1 port (never used this), and I also had a 2 port 500mA charger, so I had no problems keeping up. I bought 20 cheap Samsung 25R’s, because “everyone” on vape forums recommended them, and I totally murdered those batteries (and other more suited batteries too) on my dripper mech mod setups (between 5-7 mechs were in daily rotation, mostly 5 though, and I think it was about 3 cells pr mod in rotation pr day). It was totally my own fault I ruined these batteries. Most of my coils were around 0.1 – 0.15 ohms, and on a single 18 650 cell mech mod, this is something between 118 - 176W at 28-42 amps on a fully charged battery, which is way over the batteries specs, so it isn’t strange that I went through 20-30 not so great batteries that probably didn't even live up to the specs they were supposed to have that year, it is actually stranger that they didn’t blow up in my face:) They were taken out of rotation when they started to show sudden drops in voltage from freshly charged, so they were ruined as mech mod and vape batteries, but actually more in line with my use of the term “bad” cell. In these early could-chasing years, nobody seemed to care about ruining batteries, apart from a few boring people screaming of danger, so I blindly followed the trend. Later I became a part of the boring people:) It was a rough and stressful year, and I had messed up my nicotine strength in a 10L all vegetable glycerine batch with 10 different flavours, divided into 50 20ml bottles:(, so I didn't bother to add nikotine, but it only took me 10 months to vape through that. 

In the last 5 years I vaped, I used to mix a 5L batch with 5 different flavours every 8 months. I don’t know what your vape-all-the-time consumption is, but I vaped a daily average of about 20 ml divided on 5 mods in daily rotation (and a few puffs a day dripper setup, also on a regulated mod), and strangely enough, after 9 years of this stupid stress managing vape fixation (and 20 years of smoking), my lungs weren’t feeling great, so I quit last summer:) Send me a pm if you want to buy some regulated mods and/or batteries.

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Poor @Ash_lee_g, to see a simple question turn into a full length battery discussion :roflmao:

Anyway, sorry to chip in on this.

On 2/9/2020 at 1:30 PM, Espen R said:

I think I'll stick to my 80% charging routine, but now with an added occasional 100% charge.

I actually do believe this is the optimal way to treat your batteries. However I also agree with @mrelwood, that for the projected use of most EUC_users it won't matter to occasionally keep it at a 100% for a short period of time.

Just wanted to add that when I read the manuals, the KS16X specifically says that you should charge to 100% and leave the charger in for a few extra hours in order to allow the BMS to balance. As for the v8, it asks to charge to 100% at least once per month. So perhaps this could be taken as a guideline? :)

That being said, personally I charge my wheels to a 100% unless I will not be using them in the next 24 hours. If somehow something doesn't go as planned I try to never let them at 100% for more than  3 days.

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1 hour ago, Espen R said:

I don’t see how 300 half cycles (150 full cycles) would give me 20 000 – 40 000 km.

A ”full charge cycle” of a battery cell that we see mentioned is using the full capacity of the cell, and then charging it back to 100%. At 0% the battery voltage is at 2.5V or a bit above, depending on the cell model. No EUC will allow the average voltage go below 3.0V, and Gotway for example doesn’t go under 3.3V.

So riding a Gotway from 100% to 5% (well past ridable already) and charging it back to 100% is half a charge cycle for the cell.

Since I can reach 65km on the MSX with my regular riding style, a full cell charge cycle gets me 130km. There isn’t a difference wether I ride the wheel to completely empty twice, or if I charge between ten 13km trips. One cell charge cycle still equals 130km.

Btw, the battery voltage drops a bit faster as the charge level goes down, so if you only ride from 80% to 40%, your range is less than 40% of what you’d get going from 100% to 0%. Likewise, you have also used less cell charge cycles. (Unless the app calculates the % with a capacity compensation, which is an option on the EUC World app for example.)

1 hour ago, Espen R said:

So, I would estimate that 300 cycles, or more precise 300 50-100% charges, would get me about 14 000 – 18 000 km

Is this just a guess, or do you have any math backing it up?

1 hour ago, Espen R said:

At 7000 – 9000 km, with a possible 15% degradation, I fear that voltage drops and imbalance issues could start to occur

Since one person’s experience... etc, I do suggest that you search through the forum for ”not charging above”, ”charging only to”, etc. Just so you’ll see how soon the battery packs really can fail.

I’m not yelling these warnings because 15% of the capacity could be lost at 10 000km. But because 50% of the capacity and power could be lost at 2000km, added with a real danger of overleans (especially in the cold), and even sudden cutouts that modern wheels no longer otherwise really can get.

1 hour ago, Espen R said:

But, if I, with a 40-80% charging routine sprinkled with an occasional 95-100% balance charge, manage to get to 6500 – 7500 km on my 18XL with a fully balanced battery pack with little to no capacity loss by the end of this year, then it would at least be an indication that reducing the amount of 100% charge stress can prevent weak batteries from going bad.

As a man with interest in science, I think you know better than that. Absense of evidence doesn’t mean or even hint about evidence of absense. All correlations between any one person’s charging habits and longetivity of the pack can just as well be due to something else entirely. Considering what has been reported many times, my view would be that your pack was so incredibly well balanced from the factory, that even skipping balancing almost entirely, the pack still seems well off.

Btw, did you ever check at what voltage the pack settled to after the 100% charge?

I actually didn’t even think of this before, but even if the pack charges to 100%, there is still room for almost 0.8V of difference between lowest and highest cell. If 19 cells reach 4.28V and the BMS terminates the charge, the one cell (pair) could theoretically still be as low as 2.76V, and yet the total voltage shows 84.0V. Obviously it isn’t on your pack since your range is still adequate, but just to point out that reaching 100% does not mean that the cells are balanced.

1 hour ago, Espen R said:

Would the BMS be able to balance the battery pack with a 95% charge?

Depends on how much voltage difference there is, on how many cells, wether they have aged, how much current the BMS uses for balancing, what kind of charger you use, and how the specific BMS’s balancing curve is calculated... 😉 All I know is that it has probably started the balancing process by then.

1 hour ago, Espen R said:

The difference here is just how we use the term bad. By bad cells I meant cells not preforming as the should do, not totally broken.

Every manufactured product has a predetermined tolerance for every relevant measure. A good cell can be quite different from another good cell. For cell capacity alone it does seem that to be fit for retail, the tolerance is fairly high. ”Bad” tells us very little in terms of absolutes, so I haven’t really used it to describe unique cells, other than the ones that had reached 0V on my 16S.

If you have thought that the cells on your EUC’s battery pack were identical in the beginning, you have been profoundly mistaken. They have had easily measurable variances between capacity, original voltage, resistance, etc since day one. 

1 hour ago, Espen R said:

Still believe that provoking the weak cells with a 100% charge

Have you read somewhere that weaker cells (be it capacity or other measure) suffer from a 100% charge more than ”strong” cells? I’d love to read on this, since I have no reason to believe that there is a notable difference.

1 hour ago, Espen R said:

higher potential of causing imbalance issues than what a 40-80% charge routine does

Belief is a belief. I know that you are wrong about this.

Take a pack of perfectly healthy sheep, and let them roam freely in a grassy meadow. If there isn’t a watchdog running around, they will drift apart. Same goes for every single thing in the world where individual objects are moved, stressed, or otherwise utilized; they react slightly differently.

So far you have used the word ”believe” a few times. I’d really love to hear which of the following sentences do you believe to be incorrect:

Every cell in every pack may originally have a slightly different amount of capacity. When you ride the wheel, the weaker cells are stressed more. They lose more of their state of charge than the rest. You then charge every cell for the same amount in mAh. Now the lower cells are further from the rest than they were when you started.

 

1 hour ago, Espen R said:

by the end of this year we’ll see how my 18XL battery pack is doing.

Only if you measure the individual voltages. Which I don’t recommend.

 

1 hour ago, Espen R said:

it only took me 10 months to vape through that.

10L in 10 months?! I’ve got to stop saying that I vape a lot...! 😄 I haven’t really measured, but I think I go through about 15mL in a day.

1 hour ago, Espen R said:

Send me a pm if you want to buy some regulated mods and/or batteries.

My first reaction was that like hell I’ll buy batteries from mech mods used like that... 😉 But I assume you’d be selling ones with a bit more restricted usage history. I’ll think if I’d need any, thanks!

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@Ash_lee_g good news you found a deal that seems to work for you.

I am going to share a link to a info post at a dealer where I bought my KS16X. I added his solution of fast smart charger too. Now I am by far not a super expert on batteries, but this info post are aligned to what I know of batteries and their chemical type and behaviour. But here goes... 

https://eunicycles.eu/en/news/wszystko-o-bateriach-li-ion-w-monocyklach-elektrycznych

There are other pist out there but this made sense to me. Now adding a smart power wall plug too like @Seba tip (got myself a TP-link HS-110) I can now set a timer even on my none smart chargers so I don't overcharge too long yet have the option to balance batterycells. The sweet part is I can now monitor power consumption for charging.

But enough of that now. I hope you share some info/videos of you learning to ride once you have your own wheel @Ash_lee_g

Ohh BTW a side note for @mrelwood and @Espen R. I seem to recall @Marty Backe just charging his many wheels more or less to 100% and some might have stood some time before next use, yet he had not yet had a battery failure. I would not abuse the battery leaving it plugged in charger all time but doing small charges in the work range of the batter span isn't that big a deal as old chemistry use in old batteries. 

Edited by Unventor

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5 hours ago, Unventor said:

I am going to share a link to a info post at a dealer where I bought my KS16X.

Everything said in the link is indeed correct, but unfortunately they completely disregard the part of the charging process that does balancing, and fail to even mention that balancing occurs, and why. They also don’t translate the amount of charge cycles into any practical unit, such as distance ridden.

”It really pays off” is completely irrelevant if it extends the battery life from 10 years to 30 years, unless you excplicitely plan on using the wheel still after 10 years. And most importantly, since exactly the recommended method killed my 16S battery at around 4000km, which was somewhere around 6 months in. And the other side pack at 8000km, 12 months.

4 hours ago, Marty Backe said:

Yes, essentially all of my wheels have been charged to 100-percent and often left on the charger for 24+ hours.

I hope @Marty Backe doesn’t remember that a few years ago I was pretty loudly calling his charging habits in the lines of being inconsiderate, irresponsible and even dangerous... :facepalm: Now I know better.

Anyways, I’m having slight progress in reviving my 16S battery for the third time (now at 10 000km), and only by balancing this time since I catched the issue early on. I measured the cells to be safe for charging (1.0V lowest to highest), and after a few ”100-90-100” cycles it now charges up to 92%, or 65.7V. Slowly getting there!

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I thought I might stick this video in here since the topic shifted a little to Smart Plugs

 

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I ended up getting a KS18XL 

 

Thanks for all the info guys! I am incredibly stoked to finally have this thing, it feels amazing!!!

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18XL! Wow. Looks like you could upgrade your budget! Congratulations.

Enjoy your fantastic forever-wheel. And don't forget the appropriate protective gear (full face helmet, wrist guards, knee pads, etc.).

Did you also get a EUC bodyguard for the 18XLt? They are great value for protecting the wheel really well, during the learning phase and after that, too. I'd buy one for every wheel for which there is one, no questions asked.

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