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Should a battery last more than one year?


I now HATE Walking!!

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I got my airwheel x3 in Oct 2014 and ride it an average of 5 city blocks per day.  When it was new, I only had to charge it once per week.  By Dec 2015, I now have to charge it every day.  The battery is almost trash.  I have 3 questions:

1 - Is this normal?  Do you have to buy a new battery every year?

2 - Airwheel.net wants $320 for a battery.  Where can I get a cheaper one?  Or one that lasts longer?

3 - Should I just buy another EUC, or are they all this bad?

Thank you.

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In the EU you get 24m waranty for a device, only 6m for removable batteries as lifespan is user dependent.

A good jap batt that you keep charged at 100% almost every day, without full depletion, extreme heat or cold should not fail before 24m, but performance suffers over time; another reason to buy the biggest batt you can afford. Just get a new EUC

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Most likely it is a pack of 16 18650 batteries, take a look at the existing battery pack on the x3, look at how the batteries are arranged and its dimensions, and order a japanase battery pack with same dimensions, or if you have good soldering skill build the pack yourself, it will save some money, you may not need a bms if you monitor the dischage, and use a good quality charger, do no want to overdischarge or overcharge the cells. On your next unicycle get a much larger battery pack, and the batteries will last longer since the current draw per cell will be lower.

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  • 1 month later...

You got 15 months out of the battery, I don't think we have a lot of data points to compare that to but it's good to know. The ads tend to say that the battery will last "up to 2,000 cycles" but that doesn't mean much since they do tend to degrade and not just fail outright, as long as they're not run too hot/cold/overcharged/undercharged.

Li-Ion batteries will last longer if they're not kept at full charge.You do have to worry about the voltage going too low, but that's only likely to happen if you rode until the battery was down to nothing and then put it away without charging at all and didn't ride for at least a few weeks. Sounds like you were only charging once a week at first which should have helped as long as the charge didn't go too low.

http://batteryuniversity.com/learn/article/how_to_store_batteries

II wouldn't buy the "official" battery, that's way too expensive. You might as well get a whole new wheel at that price, then it would be all new and have a warranty. If you want to replace just the battery you can find third-party replacements, just make sure they are the same configuration like @checho mentioned. Here's an example, not endorsing this seller but just showing they're out there for a lot less.

http://www.aliexpress.com/item/lithium-ion-battery-pack-60v-2-2ah-for-Unicycle/32439567535.html

 

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All things being equal, the more batteries the Wheel has, the less each individual cell is stressed. The relationship is non-linear, meaning that if you add 25% more stress to a particular cell (stress = power & heat build-up) over a control, it could reduce a cell's lifespan several fold.

Another aspect that is rarely discussed, is that while a battery might be able to discharge at a high-rate, regenerative actions like going down a hill or hard braking creates reverse power flows that are many times higher than the specified charge rates. There is evidence to show that this places a high toll on premature cell death.

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1 hour ago, Jason McNeil said:

All things being equal, the more batteries the Wheel has, the less each individual cell is stressed. The relationship is non-linear, meaning that if you add 25% more stress to a particular cell (stress = power & heat build-up) over a control, it could reduce a cell's lifespan several fold.

Another aspect that is rarely discussed, is that while a battery might be able to discharge at a high-rate, regenerative actions like going down a hill or hard braking creates reverse power flows that are many times higher than the specified charge rates. There is evidence to show that this places a high toll on premature cell death.

This is a really interesting point.  Can anyone who has noticed "short" battery lifespans comment on what kind of hilly terrain you normally traverse?

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2 hours ago, dmethvin said:

Thanks for information!You got 15 months out of the battery, I don't think we have a lot of data points to compare that to but it's good to know. The ads tend to say that the battery will last "up to 2,000 cycles" but that doesn't mean much since they do tend to degrade and not just fail outright, as long as they're not run too hot/cold/overcharged/undercharged.

Li-Ion batteries will last longer if they're not kept at full charge.You do have to worry about the voltage going too low, but that's only likely to happen if you rode until the battery was down to nothing and then put it away without charging at all and didn't ride for at least a few weeks. Sounds like you were only charging once a week at first which should have helped as long as the charge didn't go too low.

http://batteryuniversity.com/learn/article/how_to_store_batteries

II wouldn't buy the "official" battery, that's way too expensive. You might as well get a whole new wheel at that price, then it would be all new and have a warranty. If you want to replace just the battery you can find third-party replacements, just make sure they are the same configuration like @checho mentioned. Here's an example, not endorsing this seller but just showing they're out there for a lot less.

http://www.aliexpress.com/item/lithium-ion-battery-pack-60v-2-2ah-for-Unicycle/32439567535.html

 

Thanks for information!

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On 11.12.2015 at 3:44 PM, Jurgen said:

.A good jap batt that you keep charged at 100% almost every day,

Not a good advice. Nothing except a really deep discharge makes a Lithium battery age more quickly than keeping it at 100%, especially in hot climates. For minimum battery degradation it should be kept at around 40% for as long as possible and as cool as possible when not in use, and it should only be charged to 100% immediately before use.

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39 minutes ago, mhpr262 said:

Not a good advice. Nothing except a really deep discharge makes a Lithium battery age more quickly than keeping it at 100%, especially in hot climates. For minimum battery degradation it should be kept at around 40% for as long as possible and as cool as possible when not in use, and it should only be charged to 100% immediately before use.

I been reading about that today in different web pages and I can confirm that this is absolutely right!!! Thank you for information!!!

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I bought the $90 generic jap battery.  I have not installed it yet because, duh, I thought to check my tire pressure and found it really low. Ever since I pumped it up, I get a lot more run time.  With cars, I can see the tire sitting there low. When my airwheel is parked, with no weight (me) on it, the tire looks fine. When I am standing on it, I can't see the tire.  The wheel still went just as fast with a low tire as it always did, so I did not notice a difference, but it was sucking battery big time.  With the tire pumped up, I am good for 3 miles or so.  That is far less than the 6+ miles I got when it was new, but plenty for my needs.  Well now I have a full tire, a backup battery, and a warm duh feeling in my head :)

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10 hours ago, mhpr262 said:

Not a good advice. Nothing except a really deep discharge makes a Lithium battery age more quickly than keeping it at 100%, especially in hot climates. For minimum battery degradation it should be kept at around 40% for as long as possible and as cool as possible when not in use, and it should only be charged to 100% immediately before use.

There's actually a difference between storage and using the battery. Totally different conditions.

When storaged (f.ex. after manufactured) these batt are best kept at 40%; when using it in your EUC you should keep it close to max:

you'll have optimal torque, and have less risk of too much draining and consequently damaging the cells. At 40% my wheel becomes almost impossible to ride.

Charging 100% immediately before use is not really usable with charging times of several hours. This can be solved with fast charging, but this is probably also not good for the battery.

 

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So it sounds like 40% is theoretically optimal, but not at all practical.  The question then becomes, what is the best practical solution to charging.  You can either charge every night, whether it needs it or not, or only once a week, when you get low.  It sounds like only charging when you get low is the better choice, because on average, you are closer to 40%, more of the time.  Of course, when your battery gets older, like mine, you pretty much need to charge every day, just to have juice to cover your travel needs.  

Does this sound right to you battery gurus?

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14 hours ago, Jurgen said:

There's actually a difference between storage and using the battery. Totally different conditions.

When storaged (f.ex. after manufactured) these batt are best kept at 40%; when using it in your EUC you should keep it close to max:

I would believe that most unicycle batteries are stored roughly 20h per day, what do you think? Then the question is at which percentage the battery is during this time.

Also when using the wheel, it is better for the battery to not be charged to max. Cycling between 70% and 30% instead of 100% and 10% increases the life time Whs by a factor of at least three. 

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@Niko I take your point about the battery life, and technically this is 100% correct. It's an interesting discussion technically and from an ecological POV, and not only for EUCs.

I've  tried this cycling with my Lhotz 340 the last month, because the device is expensive and I would like to get min 2year of use out of the battery

But I've given it up, because the problem in real-life is 3-fold:

- performance goes down significantly with lower battery %, f.ex. I can feel there's significantly less torque available below 80% (risk of FP)

- at 40% my wheel goes in constant alarm because it tries to prottect the battery from drawing too much current. But even if your wheel keeps running at these lower %, I don't recommend this, it's not safe and not good for the battery either (maybe worse?)

- the range you get out of a certain % is not linear: f. ex. in my case the first 25% gives me a range of 8km, the next 25% (discharge up to 50%) barely 4Km, which makes range estimation a challenge. I've been stranded already 3times around our village. I can tell you from experience, carrying a 14kg wheel is no fun not even for a few hundred meters. My wife had to come an rescue me by car 2 times.

The only viable solution that I see, whit the current wheels, is mainly for people using the EUC for their regular daily commute: in the evening you estimate the charging time based on the batt % that you have left when you arrive at home, and you plug a timer in between the socket and the charger (at your destination you do exactly the same).

For the future, I would favour an EUC with easily swapable batteries, and an intelligent charger that takes care of cycling f.ex. between 80% and 40%, with an app where you can set the cycling range, time an speed of charging. Or even better a wheel/charger with onboard diagnosis of battery condition that also adapts charging to the (changing, aging) battery condition and warns if safety issues are detected (like with electric cars). The main downside here will be cost of the charger and wheel, and because of not charging a full 100% you'll need a larger battery (which also adds weight).

 

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11 hours ago, Niko said:

I would believe that most unicycle batteries are stored roughly 20h per day, what do you think? Then the question is at which percentage the battery is during this time.

Also when using the wheel, it is better for the battery to not be charged to max. Cycling between 70% and 30% instead of 100% and 10% increases the life time Whs by a factor of at least three. 

If I understand correctly what our notable member @zlymex had mentioned before, not charging to Max and not extending the charging time after the green light has appeared does not give the BMS ample time to balance the cells. Isn't  balancing very important in order to prolong the life of the batteries?

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32 minutes ago, SlowMo said:

If I understand correctly what our notable member @zlymex had mentioned before, not charging to Max and not extending the charging time after the green light has appeared does not give the BMS ample time to balance the cells. Isn't  balancing very important in order to prolong the life of the batteries?

I dont know much about batteries but i remember from another thread that the consensus was that most of the time ( say 6 times a week, if charging every day) the battery should be charged to less than 100%, and, say 1 time should be left plugged in after the green light is lit to balance the cells. 

Practically it may be hard to achieve, especially with fast chargers and large batteries - it takes about 3.5 hrs to charge my 840wh battery with the fast charger and i usually do it overnight. It means that i have to wake up in the middle for the night to unplug the charger. 

Actually it would be great if the battery gurus could put together some kind of synopsis on the best practical ways to charge - i know we have multiple threads but an uncertainty still reigns over this item and will continue to reign. There shoukd be some kind of a semi- comprehensive recommendation considering several riding and battery size/ scenarios and the recommended charging patterns. We can then all refer to it - in the long run it may take less time to put that together and refer to it than to answer these questions every time. Who knows, maybe even euc manufacturers can benefit from this synopsis and can include it in their manuals. Anyone up for this?

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2 hours ago, SlowMo said:

If I understand correctly what our notable member @zlymex had mentioned before, not charging to Max and not extending the charging time after the green light has appeared does not give the BMS ample time to balance the cells. Isn't  balancing very important in order to prolong the life of the batteries?

My suggestion is to make a full charge once every week. Other times charge at will including not charge to the Max.

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7 minutes ago, zlymex said:

My suggestion is to make a full charge once every week. Other times charge at will including not charge to the Max.

Is it ok to do frequent recharging even if the battery is still around 30-70% and do the weekly full charge with extended hours even if the battery is just around 30-70%?

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4 minutes ago, SlowMo said:

Is it ok to do frequent recharging even if the battery is still around 30-70% and do the weekly full charge with extended hours even if the battery is just around 30-70%?

It's Ok. 30%-70% or similar cycles indeed extend battery life as suggested by ThinkPad(which use 18650 cells) and Toyota PRIUS hybrid. However, I don't think it affects battery life much so long as not to reach deep discharge often. So, charge at will.

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I fixed the battery problem(for free) of a T260 two days ago owned by one of my friends.
He described the phenomenon as: turn it on it balances normal but very soon the peddles tilt and the light red flashing. 
I came across this before and told him I can fix it.
As I expected, one pair of cells completely dead. I replaced the bad ones with two Sony 2600mAh cells:

Apart from the dead cells, other cells are also unbalanced. I then discharge the hi-V ones by electronic load and charge the lo-V ones with CC-CV power supply several times to equalize the voltages. Then I made a normal charge for 2 hours, then made a measurement:
meas.gif.1c93a9a53c38869b7b4329c080f8cc0

He bought this EUC for over a year now, how should we evaluate the battery now?
Surely two dead cells make very negative result. Otherwise the rest of the cells seems going ok with about 85% of the original capacity remains. After the measurement, I discharged the #1 and #16 manually, normal charge for 4 hours and return it back for service.;)

As for the question 'Should a battery last more than one year?', the answer would be Yes for good batteries.

More notes:
1. Batteries of T260(IPS 122) are not very good quality
2. The capacity of T260 is 240Wh, not 260Wh as the cell is 2000mAh instead of 2200mAh.
3. I personally came across more than 5 examples of dead cells or severe unbalance situations for T260
4. In the case of my IPS T260, I bought it 17 months ago, rode more than 5000km with it, manually balanced the cells twice. I measure the capacity recently: 85%(204Wh) remains.  2A load tests showed that my T260 is worse than my friend's(exclude the two bad cells).
5. The total capacity of a series connect battery pack equals to that of the weakest element/cell.
6. Poor batteries meaning drop in capacity and increase in internal resistance.
7. I cut open four battery packs made of Panasonic/Sony cells after 5 months to 1 year use, they are all very well balanced.
 

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@zlymex - Thanks for that deep dive.  Looking at nearly identical numbers, why do you say #3 is weak and #4 is not?  I am not challanging you.  Just trying to learn.

That makes me think about what the perfect EUC design could be, with respect to the battery.

The Perfect EUC would:

- Have 16 slots for 16 individual cells, with a strong securing system, so they could not bounce out.

- Have a battery calibration feature that would individually test and charge or discharge each cell as needed to balance

- Provide a health report, showing the capacity of each cell and highlight cells that need replacement.

That would be the best, but maybe a lower tech solution is also possible.  As noted above, I don't understand how the data tells which cells are strong/weak.  Could we simply attach 16 little LEDs and resistors tuned so that each LED would light if the cell were ok, and off, if it were weak?  If so, these LEDs could all be mounted on the control panel.  I assume you could only monitor the cell status, under load, when you are riding.  You would also want "monitor switch" that would simulaneously connect or disconnect these LEDs, lest they be on alll the time, draining juice.

Actually, the more I think about it, the best low tech solution may be a 17-pin AMP connector, available for $10, mounted on the control panel and providing leads to each battery junction.  You then have a cable you can plug in to a board with the LED array described above, except you can load, charge, and discharge each one too. 

What are you thoughts?

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7 hours ago, I now HATE Walking!! said:

@zlymex - Thanks for that deep dive.  Looking at nearly identical numbers, why do you say #3 is weak and #4 is not?  I am not challanging you.  Just trying to learn.

That makes me think about what the perfect EUC design could be, with respect to the battery.

The Perfect EUC would:

- Have 16 slots for 16 individual cells, with a strong securing system, so they could not bounce out.

- Have a battery calibration feature that would individually test and charge or discharge each cell as needed to balance

- Provide a health report, showing the capacity of each cell and highlight cells that need replacement.

That would be the best, but maybe a lower tech solution is also possible.  As noted above, I don't understand how the data tells which cells are strong/weak.  Could we simply attach 16 little LEDs and resistors tuned so that each LED would light if the cell were ok, and off, if it were weak?  If so, these LEDs could all be mounted on the control panel.  I assume you could only monitor the cell status, under load, when you are riding.  You would also want "monitor switch" that would simulaneously connect or disconnect these LEDs, lest they be on alll the time, draining juice.

Actually, the more I think about it, the best low tech solution may be a 17-pin AMP connector, available for $10, mounted on the control panel and providing leads to each battery junction.  You then have a cable you can plug in to a board with the LED array described above, except you can load, charge, and discharge each one too. 

What are you thoughts?

Good question and very good thinking.

The classification of week or strong is just one of my criteria evaluating the DC internal resistance at 0.5C discharge. Weak if the voltage drop equal or greater than 0.30V, strong if equal or less than 0.15V.

As regard to 'Perfect battery', there are different point of views such as
--- from the designers, they may emphasis on overall structure, reliability
--- from the manufacturer, they concentrate mainly on cost, assembly and test speed, maintenance etc.
--- from casual users mainly for show off, they see appearance most
--- from users riding long distances, they require performance and mileage.

Some of the requirements are contradictory though. Battery monitor is a standard feature on all electric cars but not on most cheap electric vehicles, they added up cost and complexity. Also, a better balancing scheme may be function at all voltage levels instead of only at 4.200V+-0.025V.

Having said that, I think adding a detachable LED array to visually monitor the cells is a very good idea especially for those EUCs such as Gotway that they don't have output protection and the power would not cut off even one cell is dead. You may use while/blue LED with turn on voltage(gradually) from about 3.1V to 3.4V which happened to be corresponding the low warning voltage of a cell. In series with proper resistors, the brightness of a LED roughly represent the voltage level of the cell.

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