Most ebikes come with a 2amp battery charger. In order to see how long your battery will take for a full charge, simply divide the total amp hour rating by the amp rating of the charger.
Example: 48v 12ah battery, 12ah / 2 amps = 6 hours (approximately)
So what if we get a faster charger and shorten the time?
This can be done, but you must be careful with the type of charge connector installed.
- The standard barrel connector found on many ebikes will be ok up to 3 amps. Although 4 amps MIGHT work, 5 amps will surely start melting the connector in many cases and is NOT recommended.
- XLR connectors are used often on 5 amp chargers or higher, so if your battery has one of these you can safely charge at a higher rate up to 15 amps - not accounting for the type of battery or BMS.
The 2nd limitation would be the battery's BMS. This is the internal circuit controlling the cell levels, both on the charge and discharge side of things. Some will not allow more than a certain charge rate. In other words, you may get a faster 5 amp charger, only to discover your battery is limited to a 3 amp charge rate.