The bike and battery has been great and regular, with no issues until now. Top up charging every now and then as has been under used for a year, always good power on demand.

This time the charge light stays green on a low battery and does not charge. Charger is fine.

Batteries 50 x 3.7 2600 show all at 3.69v except for one line of 4 that are 3.55v. is this a case of 4 dead batteries? Should I replace them and the bms, or go shopping for a new pack?

Cheers. I love my phat tyre ebike!!!!!

  • 2
    Its more than likely just one dead cell rather than 4. However my personal take on lithium batteries is that if you have to ask others about them you shouldn't be messing with them and should replace the whole pack. – Andy P Jan 21 at 10:43
  • 3 years old - did you count the number of charge cycles? Most batteries have a maximum life and this one may have done its dash. Remember a car starter battery only lasts 3 years now, 4 is very rare. Another option is to take the battery to somewhere with the skills for repacking it, and replacing any weak or out of spec batteries inside the pack. – Criggie Jan 21 at 10:58
  • So the bike was "under used" for a year or was it not used at all? If it was put away with a low/flat battery for a long time then it could have simply expired through lack of use. It happens, sadly. – Criggie Jan 21 at 11:00
  • 1
    You might take the battery and charger to a battery store such as "Batteries Plus". These guys generally have the skills to evaluate the situation, and they may be able to replace a single cell if that's all that's needed. – Daniel R Hicks Jan 21 at 13:18
  • I find the 3.69 figure very suspicious: 3.7v batteries would typically be 3.2 at 0% and 4.2v fully charged, a pack concerned with increasing charge cycles might only discharge to 20% and charge to 80% or something, furthermore I have not heard of 2600 batteries and a typo from 26500 seems strange as there's no good reason to use 26500s nowadays. I would guess that if all you say is true, then either those 4 are bad, or there is an issue with the chip. However 3 years is old, even if they are quality IMR cells, and especially if they haven't been properly cared for. – Purr Jan 30 at 22:11

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