I have an ebike conversion I did some years back. I’m now trying to get it running again after it was stored for a long time. Unfortunately the battery seems to be a bit knackered and is not taking charge (charger shows battery is full immediatley on connecting and battery gives only 1.6v not 36-42V.
Is there anyone who can help me with diagnosing/repairing this (case opens pretty easily) or mybe just wants to pronounce it dead and maybe recover some 18650 cells.
Not so sure we should be working on e-bike batteries in the space especially a faulty one! I am not so sure it is a risk worth taking , maybe work on it outside. The arch co have provided us with some concrete fireproof workbenches there!!!
I’ve built some battery packs in the past and nose-dived into a world of battery cells and what to expect. A lot of “affordable” pre-built packs are likely to have some junk cells in there, from different sources, ages, uses, conditions, specifications, brands/unbranded, assembled without proper consideration to voltages and various kinds of battery management systems (BMSs) used. If I spend the time and money on building a pack I would aim for buying a batch load of fresh Samsung cells from a reputable outlet like CellSupply and come with manufacturer certification.
Not knowing anything about your pack, there’s likely to be a bunch of cells in parallel, and bunches of those parallels in series (maybe 8 or 9 series). You can test the voltage of each of those series, they should ideally all be a similar voltage (balanced by the BMS). If one of them is way out compared to the others, there’s probably a fault with one of the cells. You could disassemble it and replace that one cell but they’re probably spotwelded together so that’s a job. Obviously, check there’s nothing physically wrong, wiring, melted parts, disconnected parts or burned cells. If there’s nothing particularly wrong with the condition or any of the series/cells, then it might just be a case of a faulty BMS which are basically replaceable. Anything further than that and you should really look at some videos explaining packs and the role of a BMS to understand what to look for or have someone help you diagnose it. There’s different BMS boards for different setups. A poor/cheap quality BMS with 100-something cells and your house could become a statistic so definitely check reviews and reputations. I’m speaking very generally of course, with more information I can maybe give more detailed advice.
It should go without saying but if you’re probing areas of the pack with anything metallic such as voltmeter probes, be careful about the potential of shorting any circuits. These packs are likely to have exposed nickel strips that span relatively large areas and are close together so make sure to keep that in mind. As mentioned, if you’re uncertain about what you’re doing or what to expect, you may wish to carry out any works on this outside, even if nothing happens you might just make people very nervous and for a good reason!
There’s lots of metal strips and so it seemed like my usual approach of getting in there with a multimeter and figuring things out may not be ideal.
It’s a decent manufacturer but I think it’s just over 10 years old now and has been sitting uncharged for so long it’s probably not worth recovering when a replacement battery now cost well under £200.
It could possibly just need reconditioning.
I posted some info about that:
JIC it’s useful.