Guide to Storing Electric Bike Batteries
Jul 12, 2016
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By Edward Benjamin, LEVA Technician Training Program
One of the problems for ebikes is this: They can spend months inactive, and that is not good for batteries. And a dead battery, damaged by misuse or neglect, is both expensive and frustrating.
Different types of batteries have different needs. Here is a rough guide:
For all batteries: Charging and using them is the best way to keep the battery in good shape. An old saying from Aviation: “To keep em flying, keep em flying…”
And another thing to keep in mind: High ambient temperatures are hard on batteries. You may remember from Chemistry 101 that if you raise the temperature by 10C, you may be doubling the rate of reaction.
Batteries are complex electro chemical reactions that operate best in the same temperature ranges that you do. High temps reduce longevity. Low temps may increase longevity, but also reduce performance.
And…there can be quite a bit of time elapse between the time the cells in an ebike battery were “formed” (battery industry word that means “activated”) and the time they arrive at your shop. So good advice is to charge all new arrivals immediately.
Guide to Storing Electric Bike Batteries:
Lead Acid Batteries (Sealed Valve Regulated Lead Acid — SVRLA) are both the most common battery used on ebikes (in total, world wide) and the ones that need the most attention. They don’t give much current if they are near freezing temperatures, and their life is rapidly reduced at high temps.
They also self discharge and to keep in shape they need to be charged at least every 3 months, more often if possible. They are not regarded as a fire risk, although they can discharge current at high rates and if shorted they will heat the wires that are shorting them and other materials white hot in seconds.
Guide: Store in a cool dry place. Putting them in the fridge when not in use is a life extender. Charge monthly. We expect these to last 1-3 years in use, and to have a nominal cycle life of about 300 cycles. Wide variation in what you will actually experience.
Nickel Metal Hydride (NIMH) used to be popular and you will still find it on some bikes. It has limitations and care issues similar to Lead Acid. They do not work below freezing, but are more durable at higher temperatures than Lead Acid.
They are self discharging, so charging them every month is best, but every 3 months at a minimum. Not much risk of fire, but again, if shorted. We expect these to last 500 or more cycles, and up to 10 years.
Lithium Batteries come in several varieties, and there is some inaccurate info pushed by some companies. The care of all the variations is the same.
Lithium Manganese is the most common at this time. These will hold a charge for more than 6 months, (some for much longer) and this can lead to laxity in keeping them charged.
Best to store in a cool dry place, and charge at least every 6 months. Fire risk, for a quality battery is extremely low, but…storing any and all lithium batteries in a way that a fire all not result in catastrophe is advised.
Lithium Iron Phosphate (LFP, or Li Fe Pho) requires similar handling. There are claims that this cannot catch fire. That is not correct and while fires are even less likely than in Li Ma, it is best to store this in a place where a fire will not become a catastrophe.
Lithium batteries can last for years, and thousands of cycles. A general rule of thumb would be that a well made quality battery will last 2000 cycles and more than 5 years.
Whether to store on the bike, or off the bike is a question that has been asked. It really does not matter – except that some bikes have features that demand a trickle of energy all the time. These bikes will discharge their battery as a result. Being alert for this and adapting your storage protocol is important.
And there are some folks who will plug the charger in, connect it, turn it on and leave it for …. days to months. This is not a good idea. While many charger are “smart” and will turn themselves off when the battery is topped off, it is possible for a malfunction charger to overcharge.
It is also possible for a charger to wear out when left on for months, and thus fail to charge the batteries. Simple advice: Don’t leave the bike and charger connected, plugged in and on for extended periods. In fact, having a timer turns the mains current off after a suitable period is a good precaution.
How to manage this? A check list, or a hang tag on the bike / battery that indicates when last charged and when needing charge next. Scrawling the date of last charge on the bike box or on tape on battery works as well. And then actually paying attention to this issue and getting the bikes / batteries charged on schedule.
By Edward Benjamin, LEVA Founder & Chairman
P.S. Don’t forget to join the Electric Bike Report community for updates from the electric bike world, plus ebike riding and maintenance tips!
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“To keep em flying, keep em flying…” Yes, that would be the solution to the charging of e-bike batteries. I travel all the time and plan to ride an electric bike around the world in 2018. The big problem is that TSA regulations make it very difficult to carry e-bike batteries aboard national and international flights. Somehow the industry must solve this problem or no one who wants to use their e-bike on long trips or for world touring will invest in such a bike. I know, I bought a bike in Europe and of course if I want to take it back with me to the U.S., I have to take it on a plane. If I don’t take the battery with me, I have to hire a battery-sitter to charge my battery until I return. I am shocked that no one in the industry is seriously working on this problem. A problem once solved that will open the floodgates for e-bike sales.
That assumption is incorrect. The “industry,” is aware and are working on it.
Specifically the makers of both the wildly popular Ebike and LEV dash, cycle analyst, and Cycle satiator, Grin tech is apparently working at building stackable batteries modules, I believe that each one is individually under the maximum allowed of wh’s or whatever to fly without restrictions. I saw a video on it about a year ago, so I’m sure it’s more fully developed by now. You can probably find out information on their site, or by calling the company.
Hi Charles,
Thank for your comment. Yes, I have been in touch with some of these companies and organizations over the past year. I am recontacting some of them, as you suggested. Will anything come out before 2018 that fits my needs, I am not sure? Yes, there is work being done, but it is not substantial and the major e-bike suppliers seem to be promoting more powerful battery packs (more watt hours, rather than less). I am producing a feature documentary on the e-bike, so any connections you have that I may not be aware of, please let me know. I would really appreciate it. Thanks again for your comment.
Hi Charles,
I contacted Ebikes.ca again, but could not find LEV dash, other than a Swedish bicycle tunnel inaugurated in 2012.
My guestion regards toping off the battery. Many times I want to start with a fully charged battery when only a couple of watt hours have been used. Does this shorten the life of the battery?
Great question ! I want to know the answer, so I can inform my customers. Typically, the battery makers will quote max available energy (Watt-hour) as a function of charge-discharge cycles. Then what is the definition of these Cycles (only full discharge-charge cycles) ?
Hi David,
If the manufacturer is not willing to give you the answers you need or if they have not been selling this battery for a long enough time to accurately supply these figures, you can look at reviews from those who have purchased their batteries previously or e-bikes using their batteries. If these do not exist, it is a big risk taking a chance on a substantial purchase of their product.
Thanks Eugene, I will search, online and also ask Phylion (the battery pack manufacturer). They use Panasonic cells.
Hi David,
You should be able to contact the manufacturer of the batteries that you ordered and find out the background on charging time, holding of a charge over time and recommended frequency of charging. The article is general recommendations on charging and not for any specific battery manufacturer.
Ed Benjamin,
Thanks for the information / good advice on eBike battery storage.
This comes at a perfect time for my startup business, since I just received a batch of Lithium batteries !
Ed,
One question :
As batteries age and go thru charge-discharge cycles, their energy storage capacity is reduced, as you know.
Any estimate on the percentage reduction over time ( at 1 year, 5 year ) ?
Hi David, Sorry, I can only say it will be different, perhaps wildly different between battery makes and suppliers. But I have no useful information on this.
Ed
Charles Halberstam, your comment was:
Grin tech is apparently working at building stackable batteries modules,
If batteries were “stackable modules”, then each module would need to be the same Voltage (for example 36 Volt DC, right ? (cells in series).
So … each module would be in PARALLEL with the others, right ?
So that means that each additional module would add amperage (Amp-hours). , right ?
How many modules would be the maximum practical quantity ?
Yes David, if each were 36v and stacked in parrallel then each module would add amperage to the overall pack. The modules can be stacked any way for both series and parallel connection (e.get if you needed 72v?) But only parallel adds Ah. Parralel also doubles (if 2 obv,) the available amp draw of the pack.
The modules I saw, seemed to be 10s 1p (36v) flat looking packs (similar to small oblong laptop style batts, encased in resin as a flat block. They looked very durable like that too.
I’m not sure where grin tech is holding in development, but for practical purposes, I’d think a 10ah pack would be a minimum, so I’d think at least four modules would be needed, if using (normal, approx,) 2500mah cells.
Thanks Charles Halberstam, for the complete explanation.
I understand the concept, but am not convinced that there is practical need. Also, this is complicate a Smart Battery Management System, right ?
I was in discussion with Grin Tech and they told me that they could supply 5 to 6 packs at 36V 2.8a and they should be ready later this year. Let me know if you get the same response. I told them I would need them for airline transport and able to be able to work together on an electric touring bike.
Yes Eugene, those were the packs I was referencing from Grin, good to know that they’re soon available in case others are interested too.
Obviously they’ll know they’re for airline transportation as that is their ‘raison d’etre!’ why they were created in the 1st place.
I don’t personally have any need for them at the moment, but unlike David, I DO think there is a practical need for them. Furthermore, the BMS doesn’t need to be more complicated just because the modules are separated? Wire doesn’t care if it’s inside a battery case or between modules when it’s connected up as a pack, so why should it be more complicated?
As people like myself look for this type of battery pack more and more companies will develop them. I know that NYCeWheels offered an Electric Brompton with two (36V 4.4amp) batteries that could be set-up in parallel to give 316.8 watt hours and still be airline legal. Unfortunately, their deal with the Chinese battery supplier went south and they told me they have not been able to get the batteries in the quantities needed.
So I just checked out the FAA rules and I see that theyou have both 100wh (no asking of Airlines permission required,) and 160wh limit, (with permission,) as well as only 2 batts allowed in total.
It actually turns out that I bought/have, two x Two (very close to qualifying,) turn key Ebike batts, made by the same company/ Factory, (Scud group,) for both my Kayman flash+ and Freway VR01 Ebikes. The Kayman is a year older, 2 ‘on frame,’ locking bar type batts, totalling 5ah each, 10ah total, and the Freway has 2 seperate compact hexagonal batteries that lock into a bottle/dolphin type frame mount. Both have on board BMS’s and the Freways have Led capacity gauges too.
Measured by their 36v nominal voltage × 5ah capacity, they give a 180+ wh capacity, but that is unfortunately 20+wh over the max I saw listed , so even with permission, they’re probably no good, however when a year old, I’m sure they’d be about 160what? So I’m not sure if they’d be legal then? The point is, if they already have these small batts that are not deliberately made for FAA rules, and they’re so close to matching, then a slightly smaller capacity batt (say 2200mah,) used in the pack build, instead of the 2500mah Samsung cell, they mostly use now, (and in my packs too,) would then yield legal air travel batts with (Imo,) very lil effort at scourcing and producing, for a new captive market.
If you are asking for permission and they only look at the markings on the batteries, they must say they are 160 watt hours or less. Sometimes they will run them through the check point station and some may be more accurate than others, like weighing baggage. I go at least a day before to try and make sure the battery will not be confiscated.
While NiCad batteries are currently difficult to source, would love to see them included in this discussion.
back to storing your battery topic and short term storage. The Grin people sell a charger than can charge up to reduced voltage, g.e. 41 V instead of 42 V for a 36 V battery. THe reason behind it is that not charging up to max voltage increases tremendously the amount of cycles a battery can be recharged over its lifespan. Still, most suppliers supply 42 V chargers and they mention: charge up your battery. It would be better to say: if you have done just a short trip on your battery, some km, and you know next time you will not need your full battery capacity, then, in that case, DO NOT recharge your battery, but store it overnight in a not fully charged state. That is the logic, is it not? But nobody expresses this logic. Why????
Hello Pedromagrela, concerning your question about overcharging: Could it be that the “smart” battery chargers know when to stop charging ? When the battery is almost fully charged,, the current flow (amperage) becomes very small. Maybe the smart chargers will then turn itself off.
Hi David. Thnks for the reply. THe matter I was mentioning is not a matter of overcharging. E.g. 42 V is not overcharging, it is kind of the limit of charging and it is this limit that most chargers will charge up to. Btw, these chargers are called smart chargers have stages of charging and protecting the battery against overcharging. The matter I was mentioning is the matter of “undercharging” in order to extent the cycle-life of the battery. E”g. for a 36 V battery , charging up to 41 V will double the number or charging ciycles this battery will stand as compared to charging up to 42 V. In order to do this you should have a smarter than smart charger, which the Grin people have, their so called satiator https://www.ebikes.ca/product-info/cycle-satiator.html.
So the question of my previous post remains: why cant you find a manual that recommends, in order to extend the battery life, not to recharge the battery after a short trip if you know that next trip you will not need all the maximum capacity of the battery.???