Click on the third link below. It is a Google Search on "e-bike battery" There are a bunch of folks selling them. The first two links are a couple of the top pages that came up. You will want to replace your battery with one of the same voltage and with the capacity called Amp-hours or Ah that is the same or perhaps a bit bigger. It is not absolutely required that you use the same type of battery but it would be best if they are the same type. The charger us usually optimized for a particular type of battery. By type I mean Lead-acid, Nicad, Nickel-metal-hydride, or Lithium. Your batter should indicate what its capacity is and what type it is.
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