battery maintenance — storing an EUC for 3 months

[jadekrane]

TLDR how do you store an EUC for 3 months without reducing the maximum storage capacity of the lithium ion battery or accidentally over-discharging it?

Or starting a fire...

 

full version

I'm travelling to the EU soon and have an InMotion V8F I need to store for 3 months.

I have a friend willing to care for the EUC while I'm gone and I want to make their life as easy as possible while also making sure the battery is properly taken care of.

I've been advised to store lithium ion batteries at 40%-60% charge to maintain their maximum storage capacity while avoiding excessive discharge.

I've also read the InMotion V8F manual for advice and they recommend charging the EUC once per month, but they didn't specify for how long or to what battery percentage. 

Here's the confusion—if 1.) you're supposed to store the battery at 40%-60%, 2.) you're supposed to charge it once a month, and 3.) the discharge rate of lithium ion batteries is relatively low at less that 5% per month, then what's the point of charging it once a month i.e. why would InMotion advise that? 

You'll take it from 40%-60% up to idk 70% then it stays at 65%-70% for a month then you charge it again the second month and it climbs even higher to 80% for a month then the third month you charge it to 100%? And now it's in the range of being overly charged for storage? Doesn't make sense yet.

Why not just get the battery to 60% charge then leave it uncharged for three months?

 

 

 

 

 

[null]

7 minutes ago, jadekrane said:

Why not just get the battery to 60% charge then leave it uncharged for three months?

Except if Inmotion has phantom battery drain, which I believe they shouldn't (?) the batteries can stay around 50% (some say nominal Voltage) for a year (and probably more) with minimal loss. I stored a KS18XL for 9 month at nominal voltage and chill temperature, and the entire pack discharged just 0,25V.

Edited July 8, 2021 by null

[meepmeepmayer]

• Make sure the charge is roughly somewhere between 30% and 90%. Don't fret about single percents. Just not totally empty or full.
• Make sure your wheel is not a Ninebot One Z10.
• Make sure the place you store it isn't wet and doesn't get cold or hot.

Put wheel there and you're done.

It will be the same charge state when you come back

[Namuhan]

Have a look at battery specifications for storage instructions. For example https://www.batteryspace.com/prod-specs/11514.pdf

[Student4Life]

I have some anecdotal experience to add to this.  I have a V8F but it's my "daily driver" so I always maintain it fully charged and at 1100 miles the range hasn't dropped.  I get at least 20miles riding hard, or at most 26 riding leisurely.  But I also have a Gotway Mten3 that I ride more occasionally, only 250 miles in about 18 months, and when I do ride it's often for short trips and then I've been putting it back on the charger and letting the BMS decide what to do.  But then for a couple of months I didn't touch it and it was on the charger (light green not red), now EUC World is telling me that my 520Wh battery drops 20% in the first mile, and if I ride it to tilt-back I can only go 16.7 miles.  Curiously my neighbor bought an Mten3 also, and after a year he wasn't riding it so I asked what happened and he told me the battery went bad.  Does Gotway use low-quality (like unbalanced cells or a "dumb" BMS) batteries in the Mten3 or would any brand/model do this?  Do I need to manually manage battery maintenance?  Can a battery be reconditioned?  How does anyone have an entire collection of unicycles, I like having a ready spare?

[Student4Life]

After reading https://noaio.com/en/how-to-maintain-batterylife-of-euc-and-scooter, I'm thinking about putting the charger bricks on a timer so they come on overnight, gives the battery time to cool down and charge during the coolest hours.  The article also mentions a "Charger Doctor" which let's you pick a charging threshold below 100%.  Supposed to extend battery life, but could also help riders who live on a hill...

[Tawpie]

3 hours ago, Student4Life said:

a couple of months I didn't touch it and it was on the charger

Probably not the best idea in the world, when you store a Li Ion battery you should charge/discharge it to around 40%, then check it monthly (or so). The lifespan of the battery is shortened by spending time at full charge… by leaving it 'on charger' for a couple of months, that likely aged the battery somewhat.

The confusing and conflicting thing about EUC/Scooter batteries is that while you don't want to leave them at 100% for months on end, if you never charge to 100% plus an hour or two after the charger turns green, the packs can become imbalanced and that can dramatically shorten the life of the pack. Search the forum and you'll find a video and pages and pages of discussion that'll let you know why. The tl:dr; is: when you're using your wheel, you absolutely do want to charge to green LED + an hour or two as often as you can.

But 'using' your wheel is different than storing it. When storing, do so at about 40%.

3 hours ago, Student4Life said:

The article also mentions a "Charger Doctor"

I think they stopped making those a couple of years ago... again, 'stopping' charge short of 100% is only in preparation for storage, not for routine use.

[Tawpie]

3 hours ago, Student4Life said:

I'm thinking about putting the charger bricks on a timer so they come on overnight, gives the battery time to cool down and charge during the coolest hours.

That's probably not necessary, although your profile suggests you are in Houston so there is that. Li Ion batteries are meant to be around humans, so they prefer temperatures that humans like. As long as it's above freezing and not in the direct sunlight on a 120° day, you're usually ok to use and charge.

I charge before I ride. That way, there's less time spent at full charge and I always have full range available. And if a wheel is out of the rotation for a week or two, post-ride it's generally below 80% so it's good to set for a while.

[Freestyler]

I would charge / discharge batteries at half, open the wheel and disconnect the batteries from the controller. Why risk any drain?

I had the batteries outside the wheel for 11 months while my wheel was waiting for repairs.

All packs had the same voltage when we measured them after all that time. (No measurements in between)

I did not notice a loss in capacity.

Maybe the cells have a harder time maintaining 4.2v, and drop to around 4.17v, but there is not enough capacity in that range to make a difference anyway.

Edited June 5, 2022 by Freestyler

[M640x]

I usually keep my wheels (4) between 40 - 80 % all the time.  I charge them up to 80 to 100% just before a ride.  When I do charge my wheels to 100% before a ride, it's just to let the bms balance them if it's needed which in most cases it's not.  Batteries are typically "matched" at the factory (internal resistance, discharge tests, etc.) and the same batch are usually built into a pack.  Per voltage, they usually don't stray too far from each other and if so it's usually a minute amount.  If I know I'm going to travel for a while, (couple months). I'll make sure my packs (wheels) are charged to 80%.  I've done this for years and it works well. 

Truth be told I'd rather bypass or remove the bms for normal operation and use it only for charging.  There are too many fault conditions that can cause a bms to cut power and not all of them are valid.  Bad for a balance device.  I have yet to see one coast to a stop after it shuts off.    I'm a very big fan of bms's in every other type of electric vehicle minus balance devices.  A different discussion for a different day.  Float On!

 

[Tawpie]

24 minutes ago, M640 said:

Batteries are typically "matched" at the factory (internal resistance, discharge tests, etc.) and the same batch are usually built into a pack.

Remember... the manufacturers of our wheels have thus far never appeared anywhere near the quality, engineering and design-for-fail-safe leaderboards. I think it was @ShanesPlanet who pointed out that "every corner that can be cut, has been cut" should be a watch phrase when it comes to EUC fabrication.

They are improving, that it true. But I'm still a very long way from putting much trust in how my batteries were designed, chosen, or built. They have to earn it, every charge and every ride. And still, they get the side eye and are banished from the house.

Edited June 6, 2022 by Tawpie

[RagingGrandpa]

On 6/5/2022 at 1:30 PM, Student4Life said:

<stored my MTen3 for 2 months with the charger connected> (light green not red)

Don't do that!!  

Forcing Li-Ion cells to remain at 4.2V by leaving a CV charger connected for weeks is bad.
It accelerates cell aging and increases fire hazard.
And it has no benefits for EUC's like MTen3, which have almost no standby drain.
Unplug during storage! 

[Begodecrashtestdummy]

Winter is starting here went out riding today in like 40 degree weather because my battery has been sitting at full charge for over a week and I’ve heard to store it for the winter months it’s best to keep it around 40% .is that true ?

[Cerbera]

Li-Poly battery packs definitely need storing at 3.85 v/cell to be safe and not to damage them, and damage starts mere hours after leaving at full charge.

Li-ion is a lot more forgiving IME, but that is still the voltage per cell to aim for.

 

[Tawpie]

1 hour ago, Dosingpsychedelics said:

Winter is starting here went out riding today in like 40 degree weather because my battery has been sitting at full charge for over a week and I’ve heard to store it for the winter months it’s best to keep it around 40% .is that true ?

yes. Reference batteryuniversity.com (Cadex corp, makers of battery test equipment and source of a great deal of information about batteries in general)

As a datapoint, when I buy LiIon cells from 18650batterystore.com, they always arrive at 3.48V. I figure if an outfit that buys and stores large quantities of cells from all kinds of sources ships them to me at 3.48, that's probably a good voltage for long term storage. Both for cell life and particularly for safety. The shipping standards for LiIon also want them at 40% or below, again for safety. Should something bad happen, there's simply less energy to deal with.

Edited December 3, 2022 by Tawpie

[Crab]

My 16x is now at 75 percent, I’m unable to ride for a week or 2 due to a fall on the ice yesterday. I could power it up and play the radio for a few hours and lower the charge?

[KiwiMark]

3 hours ago, Crab said:

My 16x is now at 75 percent, I’m unable to ride for a week or 2 due to a fall on the ice yesterday. I could power it up and play the radio for a few hours and lower the charge?

It isn't good for the lifespan of Li-Ion batteries to leave them at 100% for extended periods of time.  Leaving a battery at 75% for a couple of weeks - I doubt it would have very much negative effect.  If it were me, I'd happily leave it at that 75% until I next rode the wheel.

[Tawpie]

5 hours ago, Crab said:

My 16x is now at 75 percent, I’m unable to ride for a week or 2 due to a fall on the ice yesterday. I could power it up and play the radio for a few hours and lower the charge?

It's good as is for a couple weeks. You'd have to listen to a lot of radio, probably for the entire two weeks, to make much of a dent in the battery...

Bummer about the ice—out for a week or two sounds like nothing was (badly) broken, and that's good to hear! Heal rapidly.

[Crab]

Yea just really sore at the lower rib cage, and a bit below my shoulder but not bad. Kinda surprised it didn’t set off my Apple Watch, but my left arm was probably just floating in the air.

Edited December 4, 2022 by Crab

[alcatraz]

Hehe. That's what they recommend?

I'm just here thinking that they're trying to save a dying pack by balancing it once a month. That's probably not going to work. If it's dying within a month then it's beyond saving. 

That leads to your question too. If you happen to have a pack that's deteriorating, then you probably can't save it. If it's good you can probably leave it for years uncharged.

You should be able to extend its lifespan by using it regularly. If you can't use it, then there's no need to obsess about it. I think packs are doomed right from the factory. When cells are unmatched they develop issues along the way. And it's hard to see if they are unmatched when new. 

What's worse for the pack? To stay at 100% for years but remain balanced? OR stay at 50% but lose balance over time and maybe end up with a dead group and a wheel that won't power on? That's a good question. I think the manufacturer's writing is like trying to have the cake and eating it at the same time.

It's either one or the other, it seems. Either "don't stay at 100% for long", or "don't forget to balance regularly" (which only happens at 100%). 

What they probably should write is just. "We're rolling the dice on this pack being good. Don't store the wheel for long periods."

If only we could balance at 50%. Set some kind of storage mode. Keep the charger plugged in during storing and the bms just keeps the pack between 40-60% for years. My rambling is now over. 

[JomMas]

Last time I charged my Rockwheel,(84v/858WH) to 100% was October 16, 2021 and I rode maybe around 15 miles, down to 74 volts or so. After that ride I'd disconnected the batteries to check my, (soon to be discovered) cracked axle and just recently put her all back together. I've checked the voltage twice since then with my Charge Doctor. 

 

First check was on May 09, 2022 and it was at 73.7 volts. Then October 31, 2022 and it was at 73.4 volts. So over the course of 14 months, (with batteries disconnected), it's barely dropped at all. I had been kinda worried about it but now that I see how little effect it has, not so much anymore.

[SoleCycle]

I'm storing a wheel for probably 9 months. I'm looking for recommended battery tending options and settings to keep it in as good of condition as possible and keep it safe from any dangerous degradation.

From the bit of research I've done, it sounds like it's optimal to keep the batteries charged to about 40-50% with a low current power supply.

Unless some other great ideas are introduced to me here, I'm planning on buying a regulated, adjustable, DC Power Supply. Maybe one like this. And setting Volts to whatever voltage my batteries are supposed to be at 40%. And setting Amps to as low as possible. Then just leaving the tender on those settings for the entire time.

My initial questions are:

1. Is there an Amperage output setting that's too low for a typical BMS to recognize as a charge?
2. How many volts is 40% and 50% for a 100.8V wheel with Samsung 21700 40T batteries?
3. Once I know the minimum reasonable Amperage setting to use and a good target Voltage, is my plan generally sound?

[Chriull]

30 minutes ago, goodsignal said:

'm looking for recommended battery tending options and settings to keep it in as good of condition as possible and keep it safe from any dangerous degradation.

Healthy Li ion cells have no problem keeping the charge (more or less) over 9 month.

Only problem could be a badly designed bms or motherboard overly draining the cells. As it was with the Z10 or some Kingsong ?not shutting off/turning on? at the end of charge.

Aged cells with elevated self discharge could be a problem, too. But keeping them on a charger for 9 month would be no solution but a fire risk.

Best to check with your wheel - there should be no notable discharge after a week or a month. Maybe some "voltage settling".

Checking about every 2-3 month is a good idea anyhow.

Otherwise removing the battery from the wheel could be recommandable. No chance of accidentially turning the wheel on or malfunctions of the motherboard.

Mostly a voltage around 3.6V to 3.7V is recommended for storage.

[alcatraz]

I'm probably just repeating what Chriull wrote but here goes...

If your wheel works fine and charges fine to 100%, then you'll have no problem storing the wheel for 9 months disconnected. Ideally keep it around 50% but if you can't it's not likely you'll notice a difference afterwards anyway so....

Far more important than the 40-60% rule is that the wheel charges fine and rides a good range. It means you don't have a "leaky" pack that noticeably self discharges.

If you want to obsess about it you can have someone power on the wheel after a few months and confirm that it's still at the same charge level.

The truth is, 9 months isn't a long enough time to be risky, unless something is wrong.

[SoleCycle]

Thanks @alcatraz and @Chriull. I read through a couple guides that made be a bit paranoid about potential runaway conditions if they are left too long.

It will be so much easier to simply charge, disconnect the terminals, and not worry about it for this storage period.

Fire proof storage bags aren't that expensive, it seems. I'll probably stuff them in one of those with some desiccant packs for an extra layer of safety.