A second battery is the single upgrade that changes how far you actually ride. Carry it in a pannier and you double your day; keep one on charge at home and one on the bike and you never wait.
This is the original Kimdyma pack, not a third-party copy — Samsung lithium cells, 960Wh, with the same connector, lock and mounting rail as the battery your bike shipped with. It slides into place and locks with the supplied key. The four-LED gauge on the end cap shows remaining charge without turning the bike on, and the built-in battery management system protects against over-charging, deep discharge, over-current, short circuits and temperature extremes.
Charging: use only the supplied 48V 4A charger, which outputs 54.6V DC. A charger rated 58.8V is built for a different pack and will overcharge this one. A full charge takes about six hours.
Looking after it: if you are storing the bike for a month or more, leave the pack at roughly 40–60% charge rather than full or empty, and keep it somewhere dry between 0°C and 25°C. Charge on a hard, non-flammable surface with air around the pack, never in a stairwell or the only exit from a room, and never leave it charging unattended overnight. Stop using a battery immediately if the case is cracked, swollen or has been dropped hard — do not try to open or repair it, and take it to a battery recycling point.