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I'm a pretty good home mechanic, but very new to the e-bike world. I bought a conversion kit off eBay recently without really doing my homework beforehand. The battery pack it came with doesn't inspire any confidence now that I've read more about them, so I'd like to return it and buy a better, safer one with cells made by a reputable manufacturer.

This is the one I'd like to get (48V 13.8Ah). It comes with either Sanyo/Panasonic NCR18650GA or Samsung 1865035E cells.

Kit information:

  • Bafang 48V 500W rear-hub motor.
  • No-name 48V 17.5Ah battery, with Luhua 18650 2500mAh cells and XT60 connector.
  • I know nothing about the controller, but here's a photo of the front plate, you'll understand the numbers far better than I do.

Am I right in assuming I can purchase the battery I linked above, together with an Anderson PowerPole to XT60 adapter, and simply switch the batteries? Or am I missing some compatibility issue? I would of course also buy the dedicated charger and mounting hardware.

Thanks a lot!

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    Key thing here is battery specs. 18650' cells come in protected and unprotected, and a battery can be made of unprotected cells with protection in the battery or protected cells, or rely on protection provided by the controller. Before mixing and matching, I would ensure that the batteries had the same protection. Running a protected battery in place of an unprotected battery might work, but never run batteries without protection somewhere in teh system.
    – mattnz
    Apr 17, 2022 at 2:13
  • What did you find out that concerns you with the "No-name 48V 17.5Ah battery, with Luhua 18650 2500mAh cells and XT60 connector."?
    – Blair
    Apr 24, 2022 at 13:31

1 Answer 1

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48 volts DC is 48 volts DC, doesn't matter what battery it comes from.

There are differences in maximum current draw on different batteries - looks from the label that your controller can pull 18amps +- 1A so potentially 19amps at 48V. As long as your batteries can supply that it should work.

In theory your 17.5 Ah battery could run for almost an hour if used hard, but in reality most bikes reduce assistance when they hit the pre-programmed limiter. If you're treating this like a motorbike and using full throttle all the time without pedalling, it may not last the hour before being dead-flat.

Other issues to consider:

  • the replacement battery's casing may not fit your holder, the lock/clamps may not engage securely
  • exposed adapters are asking for water/dampness or dirt problems
  • adapters suffer from vibrations too, and either can induce arcing

The electronics questions may be more suitable on https://electronics.stackexchange.com even though its on a bike.

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  • "As long as your batteries can supply that it should work." <-- The product page says it can provide a "maximum continuous discharge current" of 25A. Is this what you mean? Apr 16, 2022 at 13:38
  • Not relevant to this question, but I feel compelled to point out that the first sentence is not universally true. Different types of batteries behave in different ways, and this can lead to compatibility issues (certain rechargeable battery types for example notoriously do not look like they’re running low right up until they suddenly run out of power). This is especially true when dealing with a separate battery controller, as the controller is generally designed to assume a specific battery chemistry (and therefore specific performance envelope). Apr 16, 2022 at 20:12
  • @AustinHemmelgarn true - but that's invisible to the controller. This is a good example of why these kind of ebike questions are really borderline on/off topic, and the more wiring/modification based ones like this could be better on Electronics.SE
    – Criggie
    Apr 17, 2022 at 0:04
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    If the batteries are not protected and controller allows over discharge of the batteries, the batteries will never be able to be charged again, so the controller may be very important.
    – mattnz
    Apr 17, 2022 at 6:37
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    @mattnz agreed - I've killed SLA batteries in my old ebike by over-discharging. That controller says "undervoltage 39 +-1" so it should cut out somewhere between 38 and 40V, which would be overdischarged for 4x 12V SLA , but probably fine for another chemistry.
    – Criggie
    Apr 17, 2022 at 10:29

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