teach you something about E-bike batteries. :-)

Discussion in 'Electric Bicycles' started by Gens Ace battery, Oct 11, 2012.

  1. Gens Ace battery

    Gens Ace battery Motored Bikes Sponsor

    Today, Let's talk about the E-bike lithium batteries. :detective:

    I am glad to share you all of my knowledge about the E-bike batteries, battery is the most expensive part in whole normal E-bike. So, you should be careful when you are going buy the battery for your E-bike.

    First, you should to learn which type battery do you want...
    Now, I am going to introduce it for you. For E-bike batteries,
    it can be made by LiFePO4, LiMn2O4, LiCoO2, and LiCoxNiyMnzO2 cells...

    LiMn2O4 battery = lithium manganate battery
    Compare with other type material cells, LiMn2O4 E-bike battery is the cheapest...the nominal voltage is 3.7V.
    It has the advantage of the low temperature. but not good for high temperature discharging...Because of its material...
    LiMn2O4 battery is not very safe... It is easy to produce the gas and swell the cell and destroy it. And the cycle life is not very long... around 400-500 times with normally 1C discharging...


    LiCoO2 battery = Lithium Cobalt oxide battery. 3.7V
    For the price, LiCoO2 battery is the most expensive one.... because at the beginning, LiCoO2 battery is design for high technology product, high level product... but it is also suitable for E-bikes... but it is not very popular because of the cost.
    The advantage of LiCoO2 battery is its energy density, For the same size, the capacity of the cells will be larger than other material cells. and it is going with light weight. and its combination property is very high...

    LiCoxNiyMnzO2 battery = lithium nickel manganese cobalt oxide battery. 3.7V
    I really do not like this name... :( :snobby: everytime, people ask me what is the material of your cells...every time I failed to speak out with that long words... hard to read it and remember it.... :(
    Ok. Let's go back to our topic, although its name is not good, but LiCoxNiyMnzO2 battery is the most popular material cell for E-bike battery market...Sanyo, Panasonic E-bike battery are this kind of cells. almost all of the famous brand E-bike are using LiCoxNiyMnzO2 batteries. The price is reasonable, the energy density and weight is good also. and it is safe. anyway, It is the best choice for E-bike if you do not need long long cycle life with more than 1000cycles... LiCoxNiyMnzO2 battery cycle life is more than 500cycles. less than 800cycles with 1C discharging...

    LiFePO4 battery = Lithium lron Phosphate Battery
    If you know something about the batteries, I think you heard something about LiFepo4 batteries before...
    Its cycle life can reach more than 1500times, even can beat 2000 cycles. It is the safest battery type for E-bike.
    There is a example, I have a Holland customer named Robert, everybody know E-bike batteries are working with BMS, It is used to protect the battery to be a safe condition. Robert told me that he is using LiFepo4 batteries, at first, it is working with BMS, but after a few month, his BMS is broken and the battery can not work anymore, then he had a idea that take the BMS out of the battery pack and connect the single battery pack with the controller... It worked and worked very well.(maybe his controller has the function of protection). But for other type material cells, it can not work without BMS, it will be easy to be broken... ( sorry, I am not encourage you that work the Lifepo4 batteries without BMS, that is not good, I will say something about the BMS part later.) And the nominal voltage of LiFepo4 batteries are 3.2V, if you want to use it to build 36V E-bike battery pack , it will need 12pcs cells connection in series. for other material type 3.7V lithium battery, it only need 10pcs cells, so the LiFepo4 batteries are more expensive and more heavy...

    For these 4 kinds of material battery. they are divided into 2 kinds of shape...

    Cylindrical metal case cells and Prismatic soft package cells.
    18650pack.jpg
    18650 E-bike battery pack.
    lipo.jpg
    Lithium polymer E-bike battery pack

    The most popular model for cylindrical metal case cell is model 18650. your laptop batteries are made by 18650 cells.
    I think it is not strange for you. For now, around more than 60% E-bike batteries are made by 18650 cells.
    The advantage of 18650 cells are cheap, easy to find, easy to connect to build the battery pack to be different shape...
    But metal case cylindrical 18650 cells are not safe... It is built by sealed metal packing,
    it will produce the gas by inside electrochemical reaction once the cells are short circuit or overcharge/overdischarge.
    then the battery will be dangerous and exploded if serious.
    18650.jpg lithium cylindrical battery explosion.jpg
    Can you image how serious it will be ? that is only 1 cell... how about 10S5P 36V 10Ah E-bike battery pack with 50pcs that kind of 18650 cells ? :rolleyes7:

    Another type is prismatic soft case lithium polymer battery, we called it as lipo...
    It is not strange for you also, you can find it everywhere... in your Mp3, Ipad, GPS. etc... they are powered by Lipo batteries. Lipo batteries are suitable for E-bike batteries. It is very suitable. It also can be made by those 4 kinds of material...and It also has Lifepo4 type. ( some people only know LiFepo4 batteries are cylindrical metal case type).
    And Lipo battery has all of the advantage which 18650 metal case have... and It is going with higher energy density, and very light weight... It can compete with cylindrical metal case 18650 cells directly... And it is much safe than 18650 although it will also produce the gas by inside electrochemical reaction once the cells are short circuit or overcharge/overdischarge when the cells are broken with serious considtion. but it will not be serious... It will not explode.
    It will be out of shape. compare with serious explosion, I think it is acceptable... just check the picture.
    View attachment 46273


    I do not know why most of brand E-bike supplier are prefer using dangerous 18650 cells to build E-bike battery...
    we did a lot research and asked lots of brand E-bike supplier why they choose 18650 cells. The answer is " because they are using it, then we follow..." that is funny...right ? actually, there are 3 big leader on E-bike battery market. Bionx, Bosch,and Panasonic... at the beginning of the E-bike, they are using 18650 cells to build it, because it is convenient and easy to find, and 18650 is the hot battery for Panasonic and Sanyo...
    But we really hope the market can move to Lipo... we are trying although we are not old for E-bike battery market.


    Now, let's move on to E-bike BMS...

    BMS is a component of E-bike battery. It is the key for E-bike battery also... The Mainly purpose of BMS is to protect the battery overcharge and over discharge, and protect the battery short circuit. And the BMS will also affect the battery discharge current... different voltage, different current using different BMS.

    To choose a suitable E-bike battery, you should to check your motor first to see its voltage requirement and the power of the motor... For example. if your motor is 36V 250W, then your battery should be 36V 7Ah minumum, of course 7Ah is too small, you can ask it larger to be around 10Ah, the capacity will affect the distance of your riding... Maybe your motor need big power over than 750W, then you will need bigger power battery to hold...just make up your mind and got the correct models...

    I am tired...:sweatdrop: That's all for today... I will keep writing when I am free and when I have something update
     
    FurryOnTheInside likes this.

  2. FurryOnTheInside

    FurryOnTheInside Active Member

    Nice work. Thank you. :)
     
  3. wheelbender6

    wheelbender6 Well-Known Member

    Great info. I agree about the BMS. Balance charging the RC batteries without a BMS can be tedious and time consuming.
     
  4. DrkAngel

    DrkAngel Member

    I have personally, over the last 8 years, built several 18650 battery packs as well as several LiPo battery packs for eBike use.
    Rode them 20,000 miles +++
    Couple NiCd too ... after suffering along with oem (patewee) lead acid ...
    Battery Builds

    Sorry, I have to take issue ...

    Until recently, LiPo has been the DIY builders battery of choice. Only the rare or occasional 18650 build has been demonstrated.
    There seems to be hardcore opposition against 18650 safety. Warnings of fire and explosions.
    Strangely, over the past 8 years, I can't recall a single incident of eBike use 18650 cells ever catching on fire or exploding.
    On the other hand ... seems almost daily there is another LiPo fire or "explosion", horror stories of burnt up bikes or burnt down garages, houses etc.

    21st century reputable brand 18650 laptop cells, except for 2006 SONY, have a fantastic safety record, much better than the supposedly safest LiFePO4!
    Maybe 100,000,000 laptops running them in the US?
    Recent advancements take this same safety proven 18650 format and multiply the capacity and surge capability.
    Becoming the builders battery of choice, LiPo builders finally becoming converts.
     
  5. jaguar

    jaguar Well-Known Member

    well probably it's all a matter of how good the charger is for the 18650, whether or not it's "smart" to keep from overcharging.
    "it will produce the gas by inside electrochemical reaction once the cells are short circuited or overcharge/overdischarge.
    then the battery will be dangerous and explode if serious."
     
  6. DrkAngel

    DrkAngel Member

    Building my own ... from used cells ...
    I carefully test and rate each cell, building banks of similar capacity and IR (Internal Resistance).
    Most importantly! I eliminate any cells demonstrating self-discharge!!!

    Not for the faint of heart!
    With comparable banks, charged to life saving reduced voltage and monitored with cell level voltage meter-alarm:
    I have bulk charged all my builds for 7+ years ... with no form of BMS !
    Typically, I re-tune (balance charge) my packs a couple times a year (if any bank varies by a couple hundredths of a volt)

    Remember! - I do monitor cell level voltages with a voltage monitor w/alarm <$2. [​IMG]
    Continuous use applies slight drain to banks 1 & 2.
    So, remove except during actual use and occasionally balance charge or supply extra charge to banks 1 & 2. (every few dozen cycles or when banks vary by > .02V)
     
    Last edited: Jul 28, 2016
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