E-Bike Battery Guide

The cheapies are China clones, the added PP are $1. The clones have high fail rates and do not have the Powerwerx warranty of one year.
oh. Never had a problem with the two I have had over the years. I would just spend the extra money and get a CA that will last a lifetime, probably, unless you get it soaking wet by leaving it exposed on the back of a car while it is raining. But the time I did that I was heading for Vancouver and a visit to Grin a few years ago. As it turns out it was a CAII anyway and they graciously swapped it out for a CAIII for the cost difference between the two models. Now I put a baggie over it held on by a small bungie.....
The Turnigy version may be just a different label, and half price. But I agree. Even the CA2.4 is well worth the $$.
@Asher has a neat write-up on using timers as a proxy smart charger to control the charging the process.


If you are interested in seeing what goes on inside the batteries, here is a cool demonstration. However, this battery is NOT what is used in E-bike batteries. Lithium as a pure metal is not used for regular 18650 batteries. The dendrite formation problem once solved, could lead to some super high-range batteries.

Winter battery care tips from E-bike School.

It is true that when you charge your batteries at very cold temperatures ( 0 deg Celsius or below), the Lithium ions get plated on the anode, which leads to capacity loss.
There are methods to overcome this by quickly heating the cell but this is not part of cell manufacturing technology. (If you want to read more: http://www.pnas.org/content/115/28/7266)

To put it in layman terms.... you can consume let's say 4 slices of pizza on a normal day but when you are ill, you can't take in the same quantity, what would happen if you still try to push the same 4 slices when your stomach is unable to accept it?

Similarly, anode in a battery can accept Li-ions at a fairly high rate when the temp is high ( late spring-summer) but when the temp begins to drop, the anode's capacity to accept the incoming Li-ions goes down and they get plated on the surface blocking the pathways. So, by charging your battery at very cold temperatures, you are blocking the Li-ion pathways in the anode material.

Micah’s book on lithium batteries is a great buy! Even if for general knowledge. His help has had me building and repairing my own batteries.
This thread is dedicated for helping new E-bike owners to understand and maintain their batteries in the best possible way.

There is a lot of confusion for any new E-bike owner as to how one should treat their batteries: Shop owners may say one thing, online resources may another thing, someone else says charge after every ride, dont worry! and few others say charge to 80%. It is painful to see so much misinformation floating around. So, you may ask why should I trust this information anymore than some random internet article. Nope, you don't have to trust me. The thread will have information that is thoroughly vetted by the scientific community and is widely accepted, not my personal opinion.

  1. I just got a new E-bike, how should I treat my battery?

    Awesome! Your eBike comes with a battery charger and give it a good look and make sure it is the right one.
    A 36V bike should have a charger that goes upto 42V or
    a 48V bike should have a charger that goes upto 54V.

    Most ebikes are shipped with batteries at 50% charge. Before your first ride, your shop should have charged it to 100%. If you bought it online, plug in your charger and charge it all the way. Once the charger reaches the 100% mark, it should turn green from red.

  2. What is the best practice for charging an E-bike battery?

    On your E-bike manual or your dealer who may not have the scientific background, may say, top it off after each ride. Yes and no. If you don't care about the longevity of the battery, just charge it after each ride, the high voltage cutoff (HVC) in the battery management system (BMS) shuts it off after it reaches 100% ( 42V for a 36V battery system or 54.5V for a 48V battery system). This practice may provide roughly 400-500 cycles before there is a substantial degradation in the cell chemistry. You simply don't have the mental bandwidth or interest in managing your battery and you are happy to replace the battery after 2 years, then you don't have to read any further.

    But, Li-ion batteries have infiltrated our lives (laptops, phones, tablets, cars). So, it can be good to know a bit more. Have you ever wondered why cellphone batteries or laptop batteries die quickly within a year or so. Plugging it in overnight is def one of the primary causes. Read on..

    What should I do?

    Charge your battery when it is not too cold or too hot. Let's say you just came back from a 50 mile ride and the battery is pretty warm ( you may not be able to feel it by touching the plastic case, but it does get warm). Leave it for 30 mins so it is back to the room temperature. Ideally, charge your batteries such that it does not sit fully charged for hours. So, if your morning commute starts at 7.30am, either charge your battery to 80% the night before or that early morning.

    You can double the cycle life of your battery by charging it only to 80%. Here is a neat infographic from Grin Tech in Canada, one of the innovators in the space.

    View attachment 23854

    They even developed a smart charger for this purpose called "Cycle Satiator". Check this out: http://www.ebikes.ca/product-info/cycle-satiator.html

    I don't have a Cycle Satiator nor do I want to invest in one!

    That's perfectly fine. You can just use the charger that came with your bike (most generic 2A chargers are made by Modiary or Shenzhen in China). Try to the keep the state of charge (SOC) between 20% to 80% if possible and enjoy your bike.

    There are other cheaper options out there that do a similar job.
    36V charger ----- 48V charger ---- 52V charger.

    If you are interested in maximizing battery life, be mindful of these two parameters:

    High temperature = BAD for Li-ion cells. So what is high temperature? Anything above 40'C or 105'F (trunk of a car on a hot summer day or exposing battery direct sunlight in Arizona or running your eBike on full turbo or throttle. One can run his E-bike on full turbo if the cell chemistry is tuned for that (Samsung 30Q vs 35E).

    Time (days or weeks) spent at high voltage = BAD for Li-ion cells. You charged it 100% and you're going away for a long weekend. This may not be a good idea.

    Everyone in the electric vehicle space knows who Elon Musk is, so I am attaching a pic of his response to this question.

    View attachment 23848

  3. How to store your E-bike battery?

    It is best to store your battery at room temperature (cool, less humid conditions) and at 50% charge. If that's not possible, just avoid storing at 100%. I am attaching a scientific article on how calendar life ageing and conditions affect the degradation. Basically, What they are saying is degradation is minimal in the 30%-70% zone.


    The paper is attached below [Predicting battery degradation in EV's].

  4. What are some of the things that can damage an E-bike (Li-ion) battery?

    Here is a neat article: by Micah Toll who has written a book on how to build Li-ion batteries from cells.
    What causes Li-ion cells to die?

    https://electrek.co/2018/05/04/are-you-killing-your-lithium-batteries/ (the comments section has some interesting responses).

    Time spent at high charge ~100% charge is bad i.e., if you leave your charger plugged in overnight, expect ~500 cycles instead of 800+ cycles. It's perfectly ok to charge your battery to 100% but keeping the batteries at 100% for days may not be a good idea.

    A fantastic video by Prof. Jeff Dahn replete with scientific insights regarding battery degradation is here. Prof Dahn is world's foremost expert when it comes to Li-ion batteries. He invented the NMC chemistry and is the current Canada research chair heading Tesla's exclusive battery research program with a university.

  5. What kind of charger should I use?

    If possible, use chargers that charge at less than 8A (most chargers run at 2A or 4A, which are perfectly fine)

If it adds any credibility, I have been an E-biker for over 4 years and have had various level of exposure into this. I am also pursuing my doctoral work on Li-ion batteries at the University of Illinois.

The thread will have only vetted, scientifically verified data on how to treat your battery. Feel free to add your thoughts and questions that might enhance one's understanding on the topic, feel free to subscribe but please refrain from posting unrelated stuff.
. Great article ! I think I'll print this out as a rough tutorial ! ??
Thanks Ravi. What about the Satiator then? What do I need to make it work with Stromer St2 battery?

My work around for that problem is:

When the ST2 charger switches from CC to CV, I just unplug the charger.
The charging happens in two stages constant current (CC) (upto 80-90%) where all the Li-ions are being shuttled back to the anode and then the charger switches to the constant voltage mode for the last 10% but it does it in a slow ramp down way.
The reason being: Imagine this.. you were driving a huge train. You can't bring it to a stop just like that.. the stopping distance is anywhere near couple of miles depending on the train speed and brakes. Similarly, all these millions of Li-ions were shuttled back and you can't stop that train just like that... ideally, you want to keep the voltage and bring down the charging current and this stage (the last 10%) is called the constant voltage (CV).

If you look on the back of the ST2 charger, they mention these two stages and how the charger light would look like. So, I used to unplug the charger roughly at about 90 to 93%.
My battery served me well for over 15,000 miles and still retains 40 mile range.
Interested in knowing what happens in your E-bike battery?

In collaboration with a successful YouTube channel, we produced a video on how Li-ion cells work.
This project took almost 4 months to get the technical animation right and provides solid visualization of the fundamentals of Li-ion cells. Hope this helps in your understanding and let me know if you have any questions.

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What happens when you charge an EV battery to 100%, all the time?
The effects can be negative for a car but for an eBike battery?

The effects are just the same . It is just that to replace an E-car battery, it is a LOT of money and for an eBike, not so much and eBikes don't experience the kind of mileage cars do. So, in a way it is not easy to compare them exactly.

Full details of what happened to a Tesla when charging to 100% has been documented here in this article and in the video below.


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[...]The effects are just the same . It is just that to replace an E-car battery, it is a LOT of money and for an eBike, not so much and eBikes don't experience the kind of mileage cars do. [...]

I suppose your mileage may vary there (pardon the pun), I have customers who have sold their cars and use their e-bikes as their only form of transportation every day! There are likely some e-car owners doing lower mileage than some of my e-bike customers. But in general your statement is probably true of the average e-car vs. the average e-bike.

Thank you for the link to that video on temperatures for battery charging. I always charge indoors, but it's a good reminder to wait at least a half hour for the battery to come up closer to room temperature (and, presumably, to let the battery chemistry settle down a bit) before putting it on charge.

I have just purchased a Giant eBike powered by Yamaha. The battery is 13.8Ah and the Smart Charger is 6A. After reading this thread I will endevaour to keep my charge between 30 and 80%, unless I forsee an extra long ride where I might charge to 100%.

The manual that came with the bake states: "After 15 normal charges, or at least every 3 months, discharge the EnergyPak completely by riding the bicycle before charging the EnergyPak again. This will increase the lifespan of the EnergyPak."

And the manual later states "There is no need to do complete discharge every time. Complete discharge every 3 months is appreciated for refressing EnergyPak management."

What are they getting at?

Is there a need to charge to 100% on occasion for "balancing" the cells?
Is there a need to charge to 100% on occasion for "balancing" the cells?

Few modern batteries come with advanced BMS where it balances the cells if one of the parallel groups go out of balance (irrespective of state of charge).
But, there are a vast majority of batteries that need to be charged to 100% to ensure the balancing is complete.
I believe they are trying to convey that.

They had an E-bike back in 2008 and the tech was still raw at that time and the batteries needed to be charged to 100% to balance it.


Since this is a 13.8Ah pack and they gave you a fast charger (6A), if I were you, I would charge the pack to 100% once every few months.
cells don't go out of balance on regular basis but if you are pushing hard and over a period of time, it may go out of balance.

if you want to go deep into the technical stuff:

Cell balancing and BMS recalibration are two different things. EVs like Tesla need not to go 100% to balance the cells. The pack architecture allows for bleeding at lower state of charge and balance the lower voltage cell group.

Sometimes these manuals are written years ago and we were all trained by annoying nickel-cadmium (NiCad) batteries (the older batteries that used to be popular in cell phone and laptop computers) to fully discharge them before recharging again. These batteries suffered quick capacity degradation – the so-called memory effect – if you didn’t do this. The good news is that Li-ion cells do not have the same problem.

Anyhow, summary is, yes do charge to 100% once every few months. No problem.