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  1. eMark

    How to increase speed simply? (Pics) chinese scooter

    Correction: The Tisto Berlin 3.0 spec says it has a 72V power plant which IMO is the way to go (power for hill climbing at 25km/h). Just the cost of converting to a 72V quality battery, motor and controller, etc, etc is expensive, besides being labor intensive with some conversion frustration...
  2. eMark

    How to increase speed simply? (Pics) chinese scooter

    What your dad really needs is a 60V power plant ... like the Tisto Berlin3.0 E-Scooter 45km/h version, 3KW https://www.sw-tuning.de/en/SW-Tisto-Berlin3-0-E-scooter-45km-h-version-3KW::47455.html https://www.sw-tuning.de/images/product_images/popup_images/47455_0.jpg Hopefully, 45m/h (29mph) is...
  3. eMark

    I guess I need to make 72v 35ah battery pack

    Do you use an internal temp sensor in the middle of your 20s7p battery pack or does the BMS shut-down the battery should the temp of any of the innermost cells gets too hot (thermal run away?). Have you run any tests to see how long you can run at MCD before innermost cells of your 20s7p reach...
  4. eMark

    I guess I need to make 72v 35ah battery pack

    If you had used plastic cell spacers instead of staggering and gluing the cells together (to save space) would your DIY battery still fit in the frame space of your bike? If you had used plastic cell spacers instead of staggering and gluing the 140 cells together (to save space) would your DIY...
  5. eMark

    Battery Amperage Concerns

    That's more for RC Lipo marketing where Lipos may have a 25C, 50C, or higher unrealistic C rating. This is used to determine the MAXimum discharge time, but no guarantee of the number of usable cycles. For example with a 50C rating and 20Ah capacity the battery should be good with a 1000amp...
  6. eMark

    I guess I need to make 72v 35ah battery pack

    As you know that's a BIG No-No ... Looks like there is no protective shrink wrap on the cells. You can't have the bare metal cans touching each other. If you were going to stagger the parallel groups (to save space) you should have two or three shrink wraps on each cell. Were you also planning...
  7. eMark

    I guess I need to make 72v 35ah battery pack

    Your phrasing may be confusing ... perhaps why no others have replied to above quote.It may have been less confusing as ... "to build a pack with 7 cells in each parallel group instead of just 5 cells in each group would minimize any voltage sag during a max discharge load". When referring to...
  8. eMark

    1 Group has more voltage sag

    https://endless-sphere.com/sphere/attachments/_mg_6859-jpg.330090/ 13s5p ... Each cell is serving as both a cell in each 13s series string as well as a cell in each 5p parallel group. Being your 14s battery is 13p it will serve you better for many more cycles than if it were only 5p.. With...
  9. eMark

    Safety of Charging Deeply Discharged Lithium Batteries.

    It's more likely to work with a newer battery (having quality name brand cells) with fewer cycles that was accidentally over-discharged. It is NOT an acceptable procedure on an older battery with cells of questionable quality or even a newer battery with no name cells of questionable quality.
  10. eMark

    van Moof S1 battery revision

    Will the lower resistance of a new 4p group of 25r cells (fully charged) be discharged to 50% SOC before any of the other nine 4p groups reach 50% SOC? That's assuming the other nine 4p groups also have the same capacity of 2500mAh when fully charged, but a higher IR than the 25r 4p group.
  11. eMark

    1 Group has more voltage sag

    You are correct (13p). What can be confusing to some is the 14 readouts in those charts. Each of the 14 readouts is the average combined parallel voltage (13p) of each of the individual series strings (14s). Each of the 182 cells is actually serving as both a cell in a series string as well as a...
  12. eMark

    van Moof S1 battery revision

    You have a 10s4p battery. The parallel group of 4 cells having only a voltage of 2.5v needs to be replaced. Each of the 4 cells in each parallel group is rated at 2750mAh when new (4 x 2.75Ah =11Ah battery capacity of your 10s4p when new). Assuming the average capacity of these used cells is...
  13. eMark

    1 Group has more voltage sag

    In your first post you said you have a 14s13p battery ... yet both of your above graphs indicate there are 14 parallel groups. A 5% additional load sag on Group 1 at 4.0V (under max load) is only 200mV which is acceptable. In comparison what is the average sag on the other 13 parallel groups...
  14. eMark

    1 Group has more voltage sag

    At 53.4V approximate average of 3.814V per parallel group except Group 1 at say 3.800 (14mV delta variance). Let it sit for 2-3 days to see if there is any increase (if any) in delta variance. Depending on amount of increase over 2-3 days (if any) suggests there is a weak/faulty cell or...
  15. eMark

    1 Group has more voltage sag

    More than 100mV (general rule of thumb) is when there is a variance among the 14 groups of at least 100mV or greater when the battery is at rest. Currently the variance ranges from only 13mV to 17mV (delta), is due only because of Group 1. Being you are cycling the battery every day it's ok as...
  16. eMark

    Weld Batterypack

    N.E.S.E. is an 18650, 21700/20700 and 26650 size cell modular system made for simple battery building and assembly which does not require special skills, tools or knowledge. Key advantages of the system: Only basic electrical knowledge required Single tool assembly. Requires only screwdriver No...
  17. eMark

    Reverse thinking...

    Agree ... it's enuf of a labor intensive reverse challenge (and expense) just converting one of the above chassis ... than starting from the ground up. Why "Reverse Thinking..." a platform chassis when there are already available options for any tweaking. You may conclude that it makes just as...
  18. eMark

    Amazon 48v battery inspection

    Well, they are pink and say 18650, but do they say Samsung 35e ? That wrapper burn through to can metal edge might be of concern if it were on the cells' positive end instead of its negative end (which is no problem). 5p times 8amp MCD = 40 amp MCD rate. Do you know if the BMS MCD rate is 30...
  19. eMark

    Small IR 18650 doesn't hold charge

    More so with 30q than other high energy dense 18650 cells. 30Q cells for whatever reason were more prone to high self-discharge being leader among the high energy dense cells. This was true with 30Q 136, 138 and 141. The newer 30Q 6T and 30Q 6 150 T don't seem to suffer from high self-discharge
  20. eMark

    Who makes the best high output 72v battery pack?

    Because it's from Grin they should be willing to offer suggestions for helping you troubleshoot (with minimal effort) to first locate fault. That's the way i'd phrase the query to Grin ... "troubleshoot with minimal effort to first locate problem" Don't mention anything about the other battery...
  21. eMark

    The Barncat Battery- No weld/no solder

    EDIT change from yesterday .... Does your battery design NOT lend itself to any existing rear hub/pedal ebike design? Getting the impression you like to fabricate your own creations ... whether it be a new battery fabrication or redesigning an ebike frame to your specification. Like you and a...
  22. eMark

    The Barncat Battery- No weld/no solder

    Really like the look (fit), practicality of your earlier (COG) location for ride safety ... Don't see this battery location as practical IF that's how you now plan to locate your 21700 battery ... Are you making a lengthier custom frame with seat a little closer to handle bars (see top...
  23. eMark

    Help me with safely wiring my batteries together in parallel

    Having a voltage variance no greater than 1.500v between the two Ego packs before paralleling is ok with packs having cells in good condition. Yes the two Ego packs will equalize while charging and hopefully during discharge, but is no indication of a weak cell that should be replaced. It's...
  24. eMark

    Help me with safely wiring my batteries together in parallel

    That is already a possibility depending on the cycle aging condition of his two Ego packs. Depending on the age of these two packs it's possible that one (or both) have already suffered some abuse resulting in voltage cell variances of 0.100v or more between the 14 cells. It's possible that at...
  25. eMark

    Help me with safely wiring my batteries together in parallel

    Easier said than accomplished AOK... depending in part on the condition of the cells in each 2.5Ah battery ... and your own DIY skill "Good Luck ... Try Not To Blow Anything Up"
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