[myzter]

hey Ragez, looks like your battery maybe 4 lead acid cells in that case ??
how many volts 48volts how many Ah ?

maybe a BMS (battery management system) is used ..
important to know before building starts ??

if you are going solar route, making a portable folding array of 4 panels (12"x12")
2 volts each panel
You can get a step up voltage booster, which can charge batteries from a 6-8V source.
In this case get 16/ 6"x6" -4 watt solar cells. these usually are .6v open voltage and 8Amps.
The solar cells will not cost as much as the voltage booster $200
and should charge your battery 50% in a couple hours