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Lithium characteristics are too different to speak in general Kokam a LiPo Manufacturer has some interesting Informations on there Website. KOKAM Infopage If you download the E-catalog from Kokam KOKAM E-info-catalog you see different Diagramms for different Types (High Power Type, High Energy Type..). See Page 8: For a High Power Type the temperature is not so important. For a High Energy Type the temperature is very important. We can not speak for all Lithium batterie types !! With lithiums batteries every manufacturer has the possibility to select production parameters which changes the characteristics of the battery completely. This makes it very complicated if we like to speak about lithium batteries. Luke

Mr. Wai Won where can i buy your drive system for my recumbent bike? Hello Mr. Wai Won, thank you Mr. Wai Won for the Information about the motor. I am cycling with recumbent bikes and like to attach an elektric system to the recumbent bike. So i am searching for drive systems which can be bought without buying the whole bike. If an e-bike has interesting performance then it is often not possible to buy the electric drive system (motor+controller+needed accessories). A sample: I have not found a possibility to buy the panasonic drive system (the system is in flyer or kalkhoff bikes). Mr Wai Won you talk about your new motor and your new controller. Very interesting to hear but ... is this drive system available to buy for me (and if i am successfully my recumbent bike friends will have that system too) Luke

Graz and austria Hi, Go to Map24 - Kostenloser Routenplaner, interaktive Stadtpläne und Straßenkarten in Deutschland, Europa, Amerika, Australien, Naher Osten und Südafrika and in the field on top of the page type graz, austria Then zoom out and you see graz and you see austria (oesterreich). Graz in more flat then my home because graz is in the southern region of austria. Graz has also a higher temperature as here in my village. And i think Graz is small but nice. If you can come with your e-bike, do some combined travel with railway + e-bike, you will see a lot of nice landscape around graz. Luke

Why i am sceptical about "cheap" lithium packs for bikes Why i am sceptical: First think about the needed current: If you use a e-bike on flat streets the needed current is in average near 4A (36V) but if you go up hills the current grow up. For 350W we need 11A and for 500W we need 16A. In my spare time i like to fly model airplanes - i use ony electric motors no gas engine. Since 4 years we fly with lithium cells (the club has 130 members and many fly electric). What we learned is that the defined discharge C rate (max. constant discharge current) on many asia produced cells are too high specified. A sample: defined on the cell is 20C measurement says max. 10C is ok see: Elektromodellflug - Yuntong LiPos im Test We learn that we can NOT go to the specified maximum C rate. If used near the maximum C rate not only the cell heats up also the livetime of the cell drops to <100 cycles instead of 300 cycles. If i look at the datasheet of some used LiIon Packs for bikes i found defined maximum discharge current of 20A (for a 10Ah pack). If the bike motor consumes eg. 350W we need 11A and for 500W we need 16A. At beginning of the live the 11A might be ok, but the 16A is too near the maximum. During the time the inner resistance grow up and the 11A will be a problem because the controller swiches of too ealy (the inner voltage drop is too high). Also i think if we use the cells near the maximum discharge current then the maximum livetime of the cell will be reduces .... sometimes dramatically. see here: http://www.buchmann.ca/article27_files/figure3.jpg 1C/1C: 500 cycles 2C/2C: 250 cycles If a cell is used near max. C discharge rate then it will - in most time - warm up during the ride. A high cell temperature speeds up the altering of the cell (oxidation of anode) which further reduce the livetime of the cell. From a manufacturer of a cell i expect not only some tabular data like max. charge and discharge rate and so on. In normal case there are diagramms and measurements available about aging and degrading depending usage temperature, discharge C rate, charge C rate ... and available capacity depending the C rate and the age, change in inner resistance during the time and so on. If you go to well known NiCd or NiMh manufacturer you will find these diagramms. If you go to mentioned Li Ion manufacturer and you will find there diagramms please send me an personal message - i have not found what i am expecting. There is more to say but i think you know now why i am sceptical... Luke

Hi Nick, i live in Austria, my native language is german. We have mountains here so if i ride my bike then i have do go up on some steep streets. This is why i like elektric bikes - but i am very careful on the battery. During hill climbing the current i need from the battery is high for a long duration. If the battery is not well suited then i haven no success during the ride and worst case the battery has reduced time to live. I am very sceptical about this "cheep" LiIon Packs we see in many actual electric bikes. I think there power density is too low to have long term success. I explain that in next post... ------------------ Here is an info about pulse power of my prefered cell: Source: Green Car Congress: A123Systems Launches New Higher-Power, Faster Recharging Li-Ion Battery Systems A123 Li-Ion Power Pulse duration C rate Power Density Continuous discharge 30 189W 2,700 W/kg Long pulse 80 240W 3,480 W/kg Instant pulse 100 344W 4,990 W/kg Luke

Hi Nick, as i understand there is a chemical reaction for longer pulses but not for instantaneous pulses like PWM Pulses in some kHz Range. My english is not very good so following are some snapshots of articles: Source: Discharging at high and low temperature A lithium-ion battery manufacturer claims that their cells perform better on a pulse rather than DC load. The DC resistance of their 18650 cylindrical cell is ~110 mOhm. At 1 KHz AC, the impedance goes down to ~36 mOhm. As the pulses increase in frequency, the cell's effective impedance goes down. This results in better performance and lower heat build-up. These two effects increase the life of the lithium-ion cell. Following is an interesting sentence !! The internal resistance of the cobalt-based lithium-ion will increase with age and cause a problem when drawing heavy pulse currents. The manganese-based cell, on the other hand, will maintain the resistance at a low level throughout its service life. The cobalt-based lithium-ion cell provides a higher energy density but manganese is better suited for pulse load applications. Source: Pulse Discharge Power Availability of a Lithium-Ion Hybrid Vehicle Battery Pack A previously validated 1-D electrochemical model of a 72 cell, 6 Ah, 276 V nominal lithium-ion hybrid vehicle battery pack is used to predict maximum discharge current for discharge pulses ranging from zero to twenty seconds in duration from various state of charge (SOC) initial conditions. Ohmic drop from open-circuit potential limits instantaneous pulse power capability (83 kW from 50% SOC) while Li\u diffusion inside negative electrode active material solid particles limits long-time capability (28 kW for a 20 second pulse from 50% SOC). Luke

Puls performance Hello, every cell has an inner resistance [Ri]. If a cell has low Ri its Puls performance is good. If the Ri is high the Puls performance is bad because the Voltage out of the Battery is Ubatt = Uinner - (I * Ri). LiIon Cell most time produced with higher energy density in mind have higher Ri. But there are some LiIonManganese Cells with low Ri like the old US18650VT. LiPo Cells are also very different. Some can be use up to C20 and others only up to C2 so it depends on the cell type if its usable or not. That is also true on every other technology. If you get a NiMh cell with very high energy density then the Ri is higher and the cell is not so useful for systems where high power density is needed. A "rule": Most time you will find that cells with high energy density has lower power density - and more often then not high energy density comes with higher inner resistance. Luke

Please be careful, (technology or type of product) Hello, LiFePO4 it not a brand it is a battery technology. There are different manufacturer so every cell has other specs. Do not reflect the behavior from one cell to all other cell types. A sample: We in the model airplane section use the A123 cells (called KonionX in europe - assembled from BMZ) with huge success because this cell can be used with high discharge rate at >20C (10Ah pack brings constant 200A). see C20 discharge diagram: Elektromodellflug - BMZ 26650-X - LiPo-FePo4 im Test At this hight discharge rate this cell lives more then 300 cycle and is not at the end of there live (this was the first year - next year we will see more cycles). In compare to the LiPo (Lithium Polymere Cells) which we also use for model airplanes. LiPo at this high discharge rate are at end of live after 100 cycles. With lower (C10) discharge rates LiPo live up to 300 cycles and are at end of live after 2 years. But when i check the website of other LiFePO4 cell manufacturer then is see that there maximum constant discharge rate is lower then that of the A123 cells. What the Killacycle can do with A123 cells is not possible with every other LiFePO4 cell. So i think we have to be careful if we speak about at technology we should speak about the type of the cell and not the technology itself. Thanks, Luke

Hello, i read in this forum about this small and lightweight tonxin (nano) motor. I found out that there is another small and lightweight motor from Suzhou Bafang Motor Science Co. LTD.: Suzhou Bafang Motor Science Co.,Ltd. Electric bike motor, Electric Bicycle motor,Shanghai Maxbright Industry Co.,Ltd. Suzhou Bafang Motor Science Co.,Ltd. ... Tongxin: CHINA HANGZHOU ZHEDA TONGXIN ELECTRIC CO,. LTD. What i found out: Both motors are 2,5kg in wight, both are brushless, both has a planetary gear.. Who knows more about the Suzhou Bafang Motor ? Torque at low RPM ? efficiency ? Reliability ? Other differences to Tongxin ? Recommendable or not ? Luke