Battery Test Results

The method of testing has been to use three 1.2Ohm 1kW resisters in series. These then draw about 21 amps from the battery pack and I time it until the low voltage trips on the BMS. With this draw I would expect to get about 2 hours of discharge (50Ah pack 80% usable). After that I would charge until HVC. After the first two cycles the pack was fairly well top balanced with all cell groups going into shunt mode before the HVC was tripped. Now my charger is rigged to go to 87.6V (24 * 3.65v) but the BMS is designed to trip at 86.4V (24 * 3.6v) so I will have to look at trimming it down a little.

  1. The BMS works.  It cuts out the charger on high volts and also cuts the throttle at low volts
  2. The wiring from the cells to the BMS should be fine as is
  3. I have some bad cells

Number three is a concern it appears that at least some cells in the 7th parallel set are not holding capacity. That set consistently hit low voltage first and at about 1.9kWh which is about half the expected capacity. Also the high voltage is tripped when the whole pack is at 83.7volts when it should be 86.4V. Now do you think that the 7th set would be in the inner or outer sections of the pack? You guessed it, they are in the inner… so I will be disassembling the pack (unfortunately) to locate and replace the bad cells. I might even test the pack outside the bike before fitting it again

I hope to do that this week.

4 thoughts on “Battery Test Results”

  1. Good luck finding the bad cells! Hey, at least you originally purchased 144 of them and only have 120 in there right now. Were you planning to use a few of the others for your 12V system?

    Overall it looks great! I am quite impressed with the battery layout you came up with. I am in the very beginning phase of my own project right now so blogs, videos, and pictures like yours are very inspiring. One question to end on, who made your motor? I read your older posts but didn’t see that listed. Thanks in advance!

  2. Thanks for the link, 103 pages though, wow! I have been all over elmoto and it is a great site. I made an introductory post and have been reading everything I can get my hands on. Right now i’m leaning towards the Headways but the larger A123s look good too if you can find them. What else did you look into before opting for the battery/motor/controller combo you went with? Thanks for the quick reply!

    1. It is a huge thread, sorry about that. I picked the Headway cells due to the size restrictions in my frame. The A123 cells “could” be jammed in (look at the Voltron race bike) but really they don’t fit well. All the large thundersky type batteries don’t give the C rating required for good performance.

      Motor and controller was a little bit trial and error. I was in the market at the time the Colossus was being developed so I jumped on board. I first tried a fairly standard 24 fet controller but I fried that. The kelly controllers have great features and a good price. I think perfect for any bike under 160volts.

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