25% range loss after just 1170 kilometers ?

[Chriull]

On 23.8.2017 at 1:57 AM, Justina said:

KingSong keeps some % of battery capacity as a reserve, to avoid damaging the battery by draining it to 0%. The % depends on the model (it can be even 20%). However, you should never drain your battery anyway.

By this the shown "percentage" of charge by the wheel are a little off from recommentations which mention some specific charge state (also a percentage, but a different one).

Fully draining the battery is about the last thing one had done to a li-ion battery... 

On 23.8.2017 at 1:57 AM, Justina said:

Just remember to charge it at least once a month and do not leave for longer periods of time, especially in winter. When you need to store for longer periods of time, keep the charge at least above 50% and charge systematically. It is all required by the manufacturers to keep the battery warranty.

Imho the death of the battery if once completely discharged is the reason why the manufacturers require full charged batteries for storage to keep up the warranty.

Unfortionately full charge is way off optimal storage conditions: (especially with elevated temperatures)

Temperature	40% charge	100% charge	Table 3: Estimated recoverable capacity when storing Li-ion for one year at various temperatures. Elevated temperature hastens permanent capacity loss. Not all Li-ion systems behave the same.
0°C	98%	94%
25°C	96%	80%
40°C	85%	65%
60°C	75%	60% (after 3 months)

(from http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries, posted and linked around here imho already quite some times...)

[Keith]

On 23/08/2017 at 0:57 AM, Justina said:

Just remember to charge it at least once a month and do not leave for longer periods of time, especially in winter. When you need to store for longer periods of time, keep the charge at least above 50% and charge systematically. It is all required by the manufacturers to keep the battery warranty.

I totally agree with @Chriull this is a nonsense. Yes, absolutely check the voltage once per month, but Lithium Ion batteries have VERY low self discharge. And will only very occasionally need topping up to storage voltage which is 3.8V/cell - this is around 40% charge level - not above 50%.

Justina's advice is what you will find on devices like Segways which have Lithium Iron Phosphate cells. These have a very high self discharge so need checking regularly, once the voltage drops below a certain level their BMS will prevent them being recharged. They are also way more tolerant of high charge levels.

When Lithium Polymer first came out we knew it was very harmful to leave them fully discharged, so used to charge them ASAP after using them. No LiPo I owned at the time lasted a second winter (leaving fully charged batteries in very cold conditions is particularly damaging we now know). 18650 Lithium Ion cells and Lithium Polymer are very, very similar in their chemistry and behaviour.

You would think device manufacturers would know these things wouldn't you, but recently I bought a powered dust mask (I do a lot of woodwork) it has a 2 off 18650 battery pack. Their appalling advice was to discharge it completely on first use and then "charge for a full 16 hours", they then went on to advise discharging fully at regular intervals before giving a full 16 hour charge, and "always charge for at least 8 hours". The charger actually takes about 4 hours from flat and has the usual red/green charge LED.

i.e. Even though the instructions regularly talk about its "Lithium Ion Battery" these were the instructions for when it used to have NiCads - or perhaps with the £103.30 a new 1800mAH battery costs they are keen to sell lots of replacement ones!  http://www.axminster.co.uk/axminster-apf-10-evolution-powered-respirator-li-ion-battery-101847

[Justina]

On 24/08/2017 at 2:40 PM, Chriull said:

By this the shown "percentage" of charge by the wheel are a little off from recommentations which mention some specific charge state (also a percentage, but a different one).

Fully draining the battery is about the last thing one had done to a li-ion battery... 

You would be surprised how many people still wait for the battery to hit 0 before charging, especially new riders... and they do this for purpose, because they think it is the right thing to do.

This is why "blocking" some % of the capacity is crucial.

 

On 24/08/2017 at 2:40 PM, Chriull said:

Imho the death of the battery if once completely discharged is the reason why the manufacturers require full charged batteries for storage to keep up the warranty.

Unfortionately full charge is way off optimal storage conditions: (especially with elevated temperatures)

 

On 25/08/2017 at 9:49 PM, Keith said:

I totally agree with @Chriull this is a nonsense. Yes, absolutely check the voltage once per month, but Lithium Ion batteries have VERY low self discharge. And will only very occasionally need topping up to storage voltage which is 3.8V/cell - this is around 40% charge level - not above 50%.

Justina's advice is what you will find on devices like Segways which have Lithium Iron Phosphate cells. These have a very high self discharge so need checking regularly, once the voltage drops below a certain level their BMS will prevent them being recharged. They are also way more tolerant of high charge levels.

When Lithium Polymer first came out we knew it was very harmful to leave them fully discharged, so used to charge them ASAP after using them. No LiPo I owned at the time lasted a second winter (leaving fully charged batteries in very cold conditions is particularly damaging we now know). 18650 Lithium Ion cells and Lithium Polymer are very, very similar in their chemistry and behaviour.

You would think device manufacturers would know these things wouldn't you, but recently I bought a powered dust mask (I do a lot of woodwork) it has a 2 off 18650 battery pack. Their appalling advice was to discharge it completely on first use and then "charge for a full 16 hours", they then went on to advise discharging fully at regular intervals before giving a full 16 hour charge, and "always charge for at least 8 hours". The charger actually takes about 4 hours from flat and has the usual red/green charge LED.

i.e. Even though the instructions regularly talk about its "Lithium Ion Battery" these were the instructions for when it used to have NiCads - or perhaps with the £103.30 a new 1800mAH battery costs they are keen to sell lots of replacement ones!  http://www.axminster.co.uk/axminster-apf-10-evolution-powered-respirator-li-ion-battery-101847

My advice was what most manufacturers require to keep the warranty valid, for li-ion batteries. For example, Inmotion clearly states to charge the battery at least once a month.

Of course, in good conditions, you won't see any significant discharge when leaving the device for a month, but winter is another story: https://www.electricunicycles.eu/all_you_need_to_know_about_rechargeable_batteries-c__224

Maybe the instruction to charge at least once a month is oversimplified, but it's better for most people than some complex maintenance instructions or no instructions at all. It is never a good idea to leave a battery for a year...

Of course there has to be a compromise. Not everyone wants to use charge doctor, keep the EUC in a separate room with climate control, and analyse charts every day to provide the best conditions for the battery. This is why the instructions should be as simple as possible, just for keeping the battery in good condition, without significant capacity loss.

Overall, material things should serve us, not the other way around

By the way: I haven't seen an EUC manual that states to discharge the battery completely. I think the major players are aware of lithium-ion batteries maintenance, so it's best to follow their requirements. If, by mistake, they advise to do something that can actually harm the battery, then it's covered under warranty.

[steve454]

9 minutes ago, Justina said:

You would be surprised how many people still wait for the battery to hit 0 before charging

Not me, I usually recharge when it gets to 50%.  Thanks for the great information.

[caelus]

Here are some interesting measurement results on partial charge benefit:

"...when you partially charge and discharge, degradation of the battery capacity is reduced. Thus, you can do over 40 000 charge/discharge cycles when going from 30% to 70% only. Or over 35 000 charge/discharge cycles from 20% to 80%; 28 000 cycles from 10% to 90%; 15 000 cycles from 8% to 92%, 7500 cylces from 6% to 94%, and the capacity reduction goes faster and faster, finally reaching 500 cycles when recharging from 0% to 100%."

[Keith]

6 hours ago, caelus said:

Here are some interesting measurement results on partial charge benefit:

"...when you partially charge and discharge, degradation of the battery capacity is reduced. Thus, you can do over 40 000 charge/discharge cycles when going from 30% to 70% only. Or over 35 000 charge/discharge cycles from 20% to 80%; 28 000 cycles from 10% to 90%; 15 000 cycles from 8% to 92%, 7500 cylces from 6% to 94%, and the capacity reduction goes faster and faster, finally reaching 500 cycles when recharging from 0% to 100%."

Wow,  you have the worst internet shit filter I have ever come across. Nothing you say or quote on this forum can be trusted at all. Whilst the sentiment is good, figures that high are complete nonsense.

You only have to look down to the comments on the link you supplied to read: "There seems to be some misunderstanding regarding the linked study. It definitely does not indicate a number of cycles in the range of 40000. Instead, Table 2 shows e.g. the total amount of charge taken from the battery is 3610Ah, corresponding to 1128 equivalent full cycles, when a partial discharge of 60% total capacity starting at 75% state-of-charge is used, i.e. from 75% to 15%."

That statement is an closer summary of the benefits of partial charge/discharge.

[Keith]

12 hours ago, Justina said:

Of course, in good conditions, you won't see any significant discharge when leaving the device for a month, but winter is another story: 

https://www.electricunicycles.eu/all_you_need_to_know_about_rechargeable_batteries-c__224

 

That article actually says: "In the case of storing one's unicycle for a longer time, e.g. throughout winters, its batteries should be charged to the level of approx. 50% and stored in the temperature of about 15 °C." 

It is extremely worrying how much you misunderstand your own website's articles. Winter is absolutely not "another story" Lithium Ion batteries stored at 50% or so and at reduced (I.e. Winter) temperatures have even lower self discharge. What is a very bad idea is charging them to 100% at room temperature and then storing them in very cold temperatures, that causes degradation of the cells as if they have been overcharged.

The article you link to does have a number of mistakes in it, not the least of which is the table of increased battery life if the depth of discharge is reduced.Where it suggests that cycling from 100% to 50% in use will significantly increase life, it is actually cycling from 80% to 30% that gets that increase - those figures have been clearly found from electric car data: None of the electric car companies charge their vehicles to a true 100%, it is more like 85%-90% - and for the very good reason of increased battery life. Unfortunately I have yet to find an EUC manufacturer who doesn't charge to at least 4.2V per cell and some BMS actually clip at 4.25V per cell which is the absolute maximum voltage before significant degradation occurs.

Oh and none of the EUC manufacturers I am aware of have a battery warrantee worth a damn. Even quite significant abuse is unlikely to wreck a battery in as little as 6 months or 1 year. I would be pretty fed up if €400-€1000 worth of batteries died in less than 3 years. 

[caelus]

4 hours ago, Keith said:

"There seems to be some misunderstanding regarding the linked study. It definitely does not indicate a number of cycles in the range of 40000. Instead, Table 2 shows e.g. the total amount of charge taken from the battery is 3610Ah, corresponding to 1128 equivalent full cycles, when a partial discharge of 60% total capacity starting at 75% state-of-charge is used, i.e. from 75% to 15%."

True, the linked study (See PDF here) does not back the 40.000 cycles claim.
Here's a Tesla Model S real world plot that reveals interesting numbers (using the Panasonic NCF18650B batteries, afaik):

"...Tesla Model S will lose—on average—less than 15 percent of its battery capacity over the average 150,000-mile (250,000-km) life of a vehicle."

That seems to support the result of approx. 1.000 "equivalent full cycles". 

[Justina]

15 hours ago, Keith said:

That article actually says: "In the case of storing one's unicycle for a longer time, e.g. throughout winters, its batteries should be charged to the level of approx. 50% and stored in the temperature of about 15 °C." 

It is extremely worrying how much you misunderstand your own website's articles. Winter is absolutely not "another story" Lithium Ion batteries stored at 50% or so and at reduced (I.e. Winter) temperatures have even lower self discharge. What is a very bad idea is charging them to 100% at room temperature and then storing them in very cold temperatures, that causes degradation of the cells as if they have been overcharged.

The article you link to does have a number of mistakes in it, not the least of which is the table of increased battery life if the depth of discharge is reduced.Where it suggests that cycling from 100% to 50% in use will significantly increase life, it is actually cycling from 80% to 30% that gets that increase - those figures have been clearly found from electric car data: None of the electric car companies charge their vehicles to a true 100%, it is more like 85%-90% - and for the very good reason of increased battery life. Unfortunately I have yet to find an EUC manufacturer who doesn't charge to at least 4.2V per cell and some BMS actually clip at 4.25V per cell which is the absolute maximum voltage before significant degradation occurs.

Oh and none of the EUC manufacturers I am aware of have a battery warrantee worth a damn. Even quite significant abuse is unlikely to wreck a battery in as little as 6 months or 1 year. I would be pretty fed up if €400-€1000 worth of batteries died in less than 3 years. 

It is worrying you don't pay attention when reading this thread. 

I've never said or advice to charge to 100% for storing batteries. I said to charge it at least once a month, but that doesn't automatically mean to charge it to 100%!

What's important is not to only prevent draining the battery, but to store it in optimal conditions, especially in winter. To save the battery properties, cyclical charging to keep it about half charged is recommended by EUC  manufacturers. 

OK, that's regarding storage. Now let's get back to normal usage: charging to complete 100% can cause capacity loss, why do you think I mentioned charge doctor? However, the capacity loss in such usage routine is insignificant comparing to loss that can be caused by frequently draining the battery to 0% or by overpowering the cells (cut-offs for instance). Of course the BMS should prevent cut-off induced damage, but there's no guarantee. 

Regarding draining the battery and charging it to 100% - not only electric cars, but most phones now prevent such behaviours. 

In the case of EUCse, this would mean blocking a significant % of capacity, decreasing the range. KingSong prevents draining the battery completely, by making the device unable to ride before complete discharge. However, charging the cells to 100% is not that harmful, so it may pass time until all EUC manufacturers will "lock" charging to for example 90% (but as far as I remember it is best to charge up to 80%, to prolong battery life span). 

Remember that users don't want to set a timer each time they charge their devices. Buying a charge doctor is an option for enthusiasts only. Users can feel free to charge their wheels to 100%, because they will change the device before having any significant capacity loss. 

Just don't drain the battery and don't overpower the device and you'll be fine. 

[MaxLinux]

7 minutes ago, Justina said:

Remember that users don't want to set a timer each time they charge their devices. Buying a charge doctor is an option for enthusiasts only. Users can feel free to charge their wheels to 100%, because they will change the device before having any significant capacity loss. 

I don't have a Charge Doctor, so I use a timer. Usually I charge when the battery level is 50%, sometimes 25%. I charge for 2 hours, then 1 hour at a time until the light turns green. After the light turns green, I usually charge for between .5 to 1 additional hour.

https://www.amazon.com/Woods-50030WD-Countdown-1-Outlet-Grounded/dp/B00FSQTSB8/ref=sr_1_13?s=hi&ie=UTF8&qid=1504916724&sr=1-13&keywords=outlet+timer

 

 

[US69]

20 minutes ago, MaxLinux said:

I don't have a Charge Doctor, so I use a timer. Usually I charge when the battery level is 50%, sometimes 25%. I charge for 2 hours, then 1 hour at a time until the light turns green. After the light turns green, I usually charge for between .5 to 1 additional hour.

https://www.amazon.com/Woods-50030WD-Countdown-1-Outlet-Grounded/dp/B00FSQTSB8/ref=sr_1_13?s=hi&ie=UTF8&qid=1504916724&sr=1-13&keywords=outlet+timer

 

 

So you always charge to 100%....why do you use a timer at all then? Just for the case you forget it on the charger?

[steve454]

1 hour ago, MaxLinux said:

I don't have a Charge Doctor, so I use a timer. Usually I charge when the battery level is 50%, sometimes 25%. I charge for 2 hours, then 1 hour at a time until the light turns green. After the light turns green, I usually charge for between .5 to 1 additional hour.

https://www.amazon.com/Woods-50030WD-Countdown-1-Outlet-Grounded/dp/B00FSQTSB8/ref=sr_1_13?s=hi&ie=UTF8&qid=1504916724&sr=1-13&keywords=outlet+timer

 

 

Do you charge for two hours, let the batteries cool down and rest for an hour or two, then finish charging?  I do that with my phone and vape batteries sometimes.  It just seems that it would put less stress on the batteries to charge them in steps, especially if they are at 50% or less when starting charging.  Probably doesn't make much difference, but the longer the charge the more heat in the batteries.  I charge my phone that way sometimes, especially if it is less than 50%, so the charger doesn't get hot for a long time and the batteries are not stressed as much.  (I think)  But then again, people seem to charge these huge battery wheels that take 12 hours to charge and leave them on the charger all night and still seem to have good battery life.

[mrelwood]

1 hour ago, KingSong69 said:

So you always charge to 100%....why do you use a timer at all then? Just for the case you forget it on the charger?

KS-16S announce 100% charge at 66.1V, which is 4.13V per cell. That is actually 93.5% of the available capacity (3.125V = 0%). Continuing the charge after that the cells slowly reach 4.2V, and BMS performs cell balancing. I'm not sure when the balancing starts, but it is recommended to perform an extended full balance charging every 10 charge cycles or so.

I bought the Charge Doctor v2 mainly for faster charging with two chargers. I have experimented with charge cutoff at 2A, 1.5A, 1A, 0.5A and 0.1A. I'm not ready to give up on the range, so I'm now using the 0.1A cutoff hoping it will still be slightly better than to leave it on for extended hours every time.

Then again, I ride 2-3 long trips every day, so most charges would be cutoff anyhow before the full 4.2V is reached. 

[Keith]

7 hours ago, MaxLinux said:

I don't have a Charge Doctor, so I use a timer. Usually I charge when the battery level is 50%, sometimes 25%. I charge for 2 hours, then 1 hour at a time until the light turns green. After the light turns green, I usually charge for between .5 to 1 additional hour.

https://www.amazon.com/Woods-50030WD-Countdown-1-Outlet-Grounded/dp/B00FSQTSB8/ref=sr_1_13?s=hi&ie=UTF8&qid=1504916724&sr=1-13&keywords=outlet+timer

Whilst a mains timer is very useful in case you forget you have left a battery on charge or, indeed as a crude way of partially charging the battery ( for example a 2Amp charger will put around 115Wh per hour back into a battery - so that is going to be around 5-6 miles range per hour)  To use it to fully charge in steps as you are doing is completely unnecessary unless you live somewhere VERY hot. Charging at 0.5C or less results in very little heating in the cell, even at the 1C or 2C rate radio control modellers fast charge LiPo's any increase in temperature of the battery is hardly noticeable.