September 8, 20241 yr Hi all Looking for a bit of advice regards my battery. Last year I had it rebuilt using new cells, which I believe are Panasonic. It went as 13ah and came back as 16.75ah. However on using it I only get around 50 to 60 miles , riding on flat trails at steady pace of 12 to 15 mph. My impression was that I would get a lot more than that. I know you will say go back to builder. Unfortunately where I had it done they are not trading any longer . So am I right to assume the milage is low, and if so what may be the cause. When I turn it on the display shows BMS ERROR . Don't know if that is relevant. Is there any way to check if BMS is faulty. Or could it be something else
September 8, 20241 yr That message means that the BMS is cutting off before the controller probably because it's out of balance, which would also account for your less than expected range. The fault is usually a result of long-term storage. To confirm the issue, you measure the battery voltage immediately after charging. It should be around 42.0v. If it's less than say 41.0v, it needs to be brought back into balance, and the first step would be to leave it on charge for a few hours after your charger gives the green light. If the above test voltage improves, repeat until it's 42v. If it doesn't improve, you have to open the battery to do some tests. As there is a small additional risk when your battery is not right, it would be best to do the above charging in a safe space.
September 8, 20241 yr Author That message means that the BMS is cutting off before the controller probably because it's out of balance, which would also account for your less than expected range. The fault is usually a result of long-term storage. To confirm the issue, you measure the battery voltage immediately after charging. It should be around 42.0v. If it's less than say 41.0v, it needs to be brought back into balance, and the first step would be to leave it on charge for a few hours after your charger gives the green light. If the above test voltage improves, repeat until it's 42v. If it doesn't improve, you have to open the battery to do some tests. As there is a small additional risk when your battery is not right, it would be best to do the above charging in a safe space. Thank you saneagle. I'll give that try
September 10, 20241 yr Author I have done as you advised. Started at 40v and after several re charges went up to 40.8 but that seems to be it.
September 10, 20241 yr I have done as you advised. Started at 40v and after several re charges went up to 40.8 but that seems to be it. I'm running out of ideas, other than it could be your voltmeter or charger. Check the charger voltage, and if it's 40.8v too, figure out which is at fault, charger or voltmeter. A gain of 0.8v is a lot, and would give you a good improvement in range if it was only a few cells low. If it was only one cell low, your range would double. Don't panic yet. Try it out now and see what you get.
September 10, 20241 yr If the cells are much out of balance, it can take quite a few balance charge attempt to get it back. If it were mine, i would go for a spin, and charge it again, leaving it on charge for a good few hours on the green light. Keep at it and bit by bit it will probably improve.
September 17, 20241 yr Author Ghost it seems to be working. Got it up to 41.2 after a couple of runs and recharges regards
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