board rev.4 is finished & ordered
2017-03-25
Battery short-circuit test FAIL
2017-05-16

It’s been a while since my last post. I’ve been waiting for several orders of pre-series components, and as it just happens everything arrives at the same time. Happy Easter! Okay, let’s process them in order of appearance.

This box with five battery packs arrived first:

It is worth to mention that some years ago, the UN has released special transportation rules for lithium {ion | polymer} batteries after severe cargo aircraft accidents caused by them. This means, these prototypes need to be contained in a rigid box, labeled accordingly.

What to do first when you receive new stuff? Take it apart!

All cells have been glued together, there is heat shrink wherever necessary, and they used polyimide tape to secure the wiring. Front and back surfaces have been isolated with adhesive stickers. They could have done better because there is still some metal shimmering through. -> Noted for series production.

The packs have been built to specification: 6S2P, 5800mAh, discharge up to 10A, charge at 5A, power and balancing ports, temperature sensor.

Next step is to verify if the packs keep their promise.

 

6 Comments

  1. tjaszewski says:

    Are these batteries and bms a part of the kick scooter?

  2. Frank says:

    Yes. It’s a a complete system consisting of charger, battery, electronics, motor, and mechanical parts.

    The BMS is a must for a professional battery pack that can pass all international safety approvals.

    But of course the battery is a battery, and can be used for anything else that is within its spec.

  3. berninia says:

    How do I get the hub motor and controller for it?

    • Frank says:

      As I wrote, sorry but I had to put this project on hold for the moment. I will continue as soon as possible. The controller is custom made, if you have read my introduction on the home page you’ll see that its features are unique. There is nothing comparable on the market, and a regular brushless motor controller will not be able to do this.

  4. berninia says:

    Please note: 6S2P 5.8 Ah does not read right. Usually the Ah applies to a cell, and not to parallel cells. Obviously the cell is not 5.8 Ah. It appears they apply 5.8 Ah to two parallel cells. Each cell being 2.9 Ah. Therefore, the energy capacity is 12 x 2.9 and not 12 x 5.8. 12 x 2.9 x 3.7 = 129 Wh. May I ask how did you arrive at 10 – 15 km range? Is this based on 129 Wh or 258 Wh?

    Also please note that a charge of 5 A implies a charge of 2.5A per cell, or 0.86C. Usually it is not recommended to charge faster than 0.5C unless the batteries are special automotive batteries.

    • Frank says:

      You are right, maybe it is clearer to say that the battery is a 22.2V / 5.8Ah / 129Wh battery pack, made from LiIon round cells in 6S2P configuration. The final cells will be Sony US18650VTC6, their nominal charging current is 3.0A.

      The 10-15 km range is based on data logging from two years of riding the vehicle with one battery pack almost every work day. The current draw is betwen 5A and 15A depending on road surface. After countless charging cycles, they have had their best time, but I am still impressed of their endurance. I will have to write a script that scans all logs and calculates the total achieved distance.

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