Chargers
Used electric bike chargers come up regularly on Cranxs, from top brands like Bosch, Shimano and Bafang, as replacements for failed units or spares to leave at work. Sellers list both new and second-hand chargers to suit most common e-bike batteries. The whole job is matching voltage and connector to your pack.
Which charger matches my battery?
Voltage comes first and there is no room for approximation. A nominal 36V battery is charged by a unit with a 42V output; a nominal 48V battery needs a 54.6V output. Both figures are printed on the charger's label and on the battery itself, so compare them directly rather than going by the bike model. The wrong voltage will at best refuse to charge and at worst damage an expensive pack.
Which connector do I need?
Bosch, Shimano and Bafang each use their own charge port, and a charger with the correct voltage but the wrong plug is useless to you. Bafang and generic kits commonly use a round barrel-style DC plug; Bosch and Shimano systems use their own proprietary connectors. Photograph your bike's charge port and compare it against the listing photos before buying. The same applies if you are powering a home-built bike — conversion kits usually ship with a matched charger, and replacing it means matching the kit's connector rather than the frame's brand.
How fast will it charge?
The current rating in amps sets the speed. A 2A charger is the standard supplied unit; a 4A charger roughly halves the time for the same pack. Faster charging runs the battery warmer, and not every pack is rated for a higher input, so check the battery's maximum charge current before paying extra for a quick charger it cannot use.
Bosch, Shimano or Bafang?
These three account for most of what turns up on the UK second-hand market. Bosch and Shimano chargers are matched to their own batteries and are not cross-compatible with other systems even where the voltage looks right, so buy within the ecosystem your bike came with — the same discipline applies to displays and motors. Bafang and generic units are more interchangeable, provided the voltage and plug agree.
What should I check buying used?
Ask the seller to plug it in and confirm the status LED lights and changes state. Check the mains lead is a UK three-pin (a detachable IEC lead is cheap to replace if not), and run your fingers along the output cable feeling for kinks or fraying where it meets the strain relief at each end — that is where these fail. Look over the casing for cracks, scorch marks or a rattle that suggests it has been dropped. A charger that gets warm in use is normal; one that gets hot, buzzes, or smells is not worth any price.