Question abt. Lithium ion battery shelf life before purchase

[Onweelsagain]

I participated here for a while in 2008-2009 after purchasing my first ebike. (I was Onweels but it was so long ago my email and password were long gone so I registered again) My first ebike had/has no brand name, was made in China, with a 350 watt hub motor which was originally run by a 10 amp hour, 36 volt Phylion battery. The battery was 14 months old when I purchased it and it began having problems after a few months. After a year and a half it was so unreliable it sat unused for a few years. Then I replace the battery with a LifePo4 Ping battery with 15 amp hours which has lasted about 2 and an1/2 years and still seems to have sufficient capacity for what I need. But going up a big hill something went POP and now although the motor still runs the bike, the pedals go round and round connecting to nothing. And I need the pedel assist as there is really big hills here. The ebike repair guy here thinks the freewheel has broken and it should be easy to fix, but as I have been saving for a new more powerful ebike for a while, and as my bike is pretty old, I am wanting to buy a brand new 500 watt Cargo bike. The bike I want has a 48 volt 15 amp hour lithium ion battery with 18650 I think it says) ?SD1 Samsung cells.

But it sounds like the new unpurchased bikes and batteries have been sitting in storage well over a year and I have concerns about getting another battery that may have used up a substantial proportion of it’s life sitting on a shelf somewhere. I am thinking battery technology has improved a lot in the past 10 years, and maybe they retain their freshness a lot better now if they sit around over a year, but I am not sure, and I would like to hear some opinions on this.

The seller is testing the battery for me, and I am wondering if the battery charges to 4.2 volts (which I think is what the capacity would be if the pack was fresh) if that means it’s life span will be as good as if I got it when it was manufactured only a couple months ago? If it charges to the optimal voltage it should have the capacity to hold, will the battery probably last just as long as a newer one, or is there some calendar aging related cliff it may drop off prematurely in the future?

If the battery charges to less than 4.2 volts, and the low voltage shut off point is about 3.0 volts, how is the remaining capacity calculated? Like if the battery will only charge to 4.1 volts or 4 volts, when it should be able to charge to 4.2, how much actual usable capacity would the battery have lost?

As you can tell by my questions I only vaguely understand the technical stuff and just want to make sure I don’t end up with a battery that is already well into middle age.

After the last bike and premature battery problems, I would really appreciate knowing how to evaluate this battery, before purchasing this bike!

 

[wheeliepete]

Welcome back to the forum Personally I would view the bike as needing a new battery and the price adjusted accordingly. If you get some use from it, it's a bonus. End of charge voltage can be very misleading as the test comes when it's put under load. If the battery pack has been well looked after, charged to around 37v, then checked and topped up if necessary every couple of months, then it may well still have a reasonable life span, but this is pretty unlikely in the real world. Ask the seller for this information. Unless he tells you he has just taken it on a 25 mile test ride and the battery still has charge, disregard anything they tell you. "Battery seems fine", doesn't cut it and is completely meaningless.

 

[Onweelsagain]

If the battery pack has been well looked after, charged to around 37v, then checked and topped up if necessary every couple of months, then it may well still have a reasonable life span, but this is pretty unlikely in the real world. Ask the seller for this information.

Thanks for the welcome back!

The brand new bike and battery are still in the box the factory packed them in, or were until the seller took it out to test the battery. The battery was charged at the factory, but has never been unpacked, charged, or maintained since it was made well over a year ago...

It is really helpful to know I cannot evaluate the battery just based on what voltage it reaches right after it is charged. I did talk to the seller briefly about some sort of discount if the battery has lost a percentage of capacity, but really I would rather just pay the full price for a newer battery. Especially as it sounds difficult to calculate what percentage of capacity has been lost. I think the battery has a 2 year warranty but I need to clarify that. (the seller said it was a guarantee that after 1 year it would still have 70% capacity. But the company making the bikes says 2 years or a certain number of charge cycles) I am not sure if this is a reasonable guarantee or not? I would like to hope the battery would be good past the minimum guaranteed by the warranty ...

 

[wheeliepete]

Find out exactly what warranty the seller will give you and go from there. There is no doubt the life of the battery has been shortened by age, storage and lack of use, but by how much??? I'm afraid the only real test will be use and time.

 

[Onweelsagain]

This must be a really common situation for anyone buying an ebike with a factory made battery. It seems there would often be the shipping time in a cargo container that may or may not be climate controlled, and the time the battery sits in a store or warehouse waiting to be purchased and used for the first time. Is over a year really an unusually long of a time for a battery to wait to be sold to the consumer? Are there any industry standards around this? How can the average ebike user who can't do their own battery testing know if the new battery on the bike they are buying has already burned through 1/4 or 1/2 it's life sitting on a shelf?

A 2 year warranty from the day I purchase the bike would sort of put my mind at rest if it was specific about what would be considered a non functional battery. If after 18 months the bike can only go 8 miles, and it's original capacity was 20 miles, for me that would be a useless battery, but for someone else not a big problem. And if it takes enough of a charge to go 2 miles maybe that would also be considered "still working" The seller mentioned a guaranteed 70% remaining capacity after one year, but if there is no objective test to measure that it seems meaningless.

I am not clear how a batteries remaining capacity should be measured...?

It seems there should be a way people buying a new never used ebike and battery can know this?

 

[flecc]

This must be a really common situation for anyone buying an ebike with a factory made battery. It seems there would often be the shipping time in a cargo container that may or may not be climate controlled, and the time the battery sits in a store or warehouse waiting to be purchased and used for the first time. Is over a year really an unusually long of a time for a battery to wait to be sold to the consumer? Are there any industry standards around this? How can the average ebike user who can't do their own battery testing know if the new battery on the bike they are buying has already burned through 1/4 or 1/2 it's life sitting on a shelf.

A 2 year warranty would sort of put my mind at rest if it was specific about what would be considered a non functional battery. If after 18 months the bike can only go 8 miles, and it's original capacity was 20 miles, for me that would be a useless battery, but for someone else not a big problem.

I am not clear how a batteries remaining capacity should be measured...?

It seems there should be a way people buying a new never used ebike and battery can know this?

A 2 year battery warranty is the norm for good quality e-bikes, and that dates from the day of purchase. Experience shows that they don't lose a lot of capacity during initial storage, that mainly happens once the battery is in full use. The only precise way to measure exact capacity is to use it all on the bike while measuring what's passing through on such as a Cycle Analyst.

The reason it cannot be measured on the spot is that there is no current in a battery, only a chemical potential to produce current when it's connected, batteries being chemical devices that are primed during charging.

Think of a chemical battery as being like a power station. One cannot connect a meter to a 13 amp socket and measure the electricity at the nation's power stations because there isn't any stored, it's only produced in answer to demand. That's just what batteries do, use chemistry to make it on demand when you ask for it.
.

 

[wheeliepete]

I'd never really considered the points you raise, but like flecc says, most people will just rely on the warranty given. I have seen dates of manufacture on Bosch battery boxes, but I guess that is just the box and no indication of the age of the cell inside the battery. I wouldn't worry to much if you feel the seller will stand by his warranty. You will notice if the battery capacity starts to drop off.

 

[Onweelsagain]

Thank you for trying to explain this Wheeliepete and Flecc!

It was Flecc who helped me figure out I had a battery problem from an old "new" battery close to 10 years ago!

And it is a relief to know the more modern batteries don't usually loose much capacity before they are sold!

Does anyone here have any idea how long from the day they are manufactured, lithium ion batteries on average sit waiting to be sold, and at what point the length of this wait period should be a concern? (presuming a wait period at about a 60 degree average temperature at a optimal storage charge) For a non technically inclined ebike user/ buyer, it is sort of like buying a $1000 tub of yogurt with no best before/ sell by date...

And if a 2 year warranty is standard, what would normally be considered an unacceptable loss of capacity within this 2 year period?

 

[flecc]

And if a 2 year warranty is standard, what would normally be considered an unacceptable loss of capacity within this 2 year period?

This varies considerably since it depends on several usage factors and the battery quality:

Frequently completely emptying a battery shortens life.*

Too frequently topping up to full shortens life.*

High discharge rate by a powerful motor shortens life.

In summary using a top quality battery sensibly might only see under 10% loss of capacity in two years, going on to a five year life.

Conversely using an average battery with a high power motor to the full while falling foul of the first two above regularly might well lose 30%. In the worst case a battery can fail at 2 years due to being unable to supply enough current under high load, such as when hill climbing.

It is a bit of a lottery really, due to the great variation in conditions of e-bike use.

* These are because the greatest chemical stress for the cells is at full charge or reaching empty. By all means charge to full, but not every time you do two or three miles for example.
.

 

[Sturmey]

And if a 2 year warranty is standard, what would normally be considered an unacceptable loss of capacity within this 2 year period?

My bike guarantee from Halfords is very specific here. The battery is guaranteed to 60% of its capacity, which I presume is equivalent to a 40% loss. (The Phylion battery has a 'smart BMS' and the user can view this by holding down the 'on' button for 10 seconds)
I have seen this 60% figure mentioned elsewhere, so I would presume its a norm in many cases.

 

[Onweelsagain]

Flecc, I know it is true that how a battery is treated will have a lot of affect on it's capacity loss over the years, and the warranties generally cover them for what would occur with responsible use but not abuse.

I am the "Large Little Old Lady Who Only Drives to Get Groceries on Mondays" type of ebike user. I usually only go to town once a week, which is a 10 mile round trip with some big hills. So I usually charge my bike battery to 100% just before I leave, ride it in and back and then leave it sit partially charged for another week. And I would be doing the same with the new lithium battery, though from what I am reading if it has enough capacity it might be best for the battery to only charge it to 80 -90%

I am still having a hard time getting my head around how a batteries capacity is evaluated. Part of what I am hearing sounds sort of like the workings my irrigation tube that I use to slowly siphon a dribble of water into a barrel from a very limited output spring. The water I get in the lower barrel is limited by both the capacity of the spring, but also the diameter of the irrigation tube which tends to get cruded up and diminish over time.

I guess a simple way to estimate capacity and keep track of a batteries gradual loss of capacity would be to ride the bike with a new battery around a loop keeping tack of the distance covered, and then do the same test in a year and two years and 3 years.. ?

The new bike I want has 4 lights on the handlebars that when the bike is at rest will give a general idea of the charge left in the battery. The user manual says it needs to be charged if it is down to 2 lights and urgently needs to be charged if it is down to 1. So maybe the difference over time, in the distance covered when the first 3 lights go out would be a rough way to estimate lost capacity? And if when the battery is new the first light goes out and stays out when the bike is at rest, very quickly after a full charge, maybe that would suggest the battery had lost considerable capacity in storage?

I used a cheap possibly inaccurate multimeter to check my 15 amp hour 36 volt LiFePo4 Ping battery and even after 2 and a 1/2 years (before the free wheel broke) the Ping battery has very consistently always had 39.1 volts left after my town trip, which would drop to 39.0 if I left it for 2 weeks. Ping recommends the battery be charged if it drops to 38.4 volts, but I never let it go below that. But Ping helped me set up a on off circuit breaker switch in between the red and black Anderson connectors that I used to plug the battery into the bike with no current flowing because I was scared of sparks. This allowed me to make sure the battery was disconnected from the controller when no in use so it did not get incrementally drained.

Anyways.. I do take very good care of my batteries and tend to worry about their charge and storage conditions quite a bit, which is another reason I want to know the new battery is healthy to start with

Stumey, thanks for sharing your own experience with warranties!