For little money you can buy a 48V 3A e-bike battery charger via the usual channels, which can neither shine with performance nor inner values. A purchase is not recommended.
Tage d: Battery
Power banks are a convenient means of choice for supplying small projects such as IoT, streaming or sensors. But what's with low quiescent current, efficiency and maximum performance? Ideally the cells should be Exchange or compile initial. Pre tipped (cheap) power banks...
Battery charger on the basis of the BQ24450 (UC3906) with isolated input to load several AGM/GEL cells in series.