How to Read a Scooter or Hoverboard Charger Label
Quick answer
The OUTPUT line is what matters. "42V 2A" means the charger delivers up to 42 volts at up to 2 amps. The replacement's output voltage must match exactly; its amps can be equal or lower (slower charging) — higher is only safe if your battery supports it.
INPUT vs OUTPUT
Every charger label has two electrical ratings. INPUT is what the charger takes from the wall, for example "INPUT: 100–240V ~ 50/60Hz 1.5A". The wavy ~ symbol means AC. A 100–240V range means the charger works on both US and European outlets.
OUTPUT is what the charger delivers to your scooter or hoverboard, for example "OUTPUT: 42V ⎓ 2A". The ⎓ symbol (a solid line over a dashed line) means DC. This is the line you use to find a replacement.
What "42V 2A" means
The first number is voltage. Lithium-ion scooter and hoverboard chargers are constant-current / constant-voltage chargers: they push current until the pack reaches the set voltage, then hold that voltage while the current tapers off. 42V is the full-charge voltage of a 36V (10-cell) battery.
The second number is current in amps. 2A means the charger can deliver up to two amps. A 10Ah battery charged at 2A takes roughly five to six hours from empty; at 1A it takes about twice as long.
Some labels show watts instead of or as well as amps, e.g. 71W. Watts = volts × amps, so 42V × 1.7A ≈ 71W.
Why volts must match exactly
Common output voltages are 29.4V (24V packs), 42V (36V), 54.6V (48V), 58.8V (52V), 67.2V (60V) and 84V (72V). Each is simply the number of cells in series × 4.2V. A charger with a higher voltage overcharges the cells and can start a fire; a lower one never fills the battery.
Older lead-acid scooters such as the classic Razor E100 and E300 are different: their chargers are rated around 24V for a 24V sealed lead-acid pack and must not be swapped with a lithium charger.
Why amps can be equal or lower
The battery only draws the current the charger allows. A lower-amp charger at the right voltage is gentle and simply slower. A higher-amp "fast" charger can be fine for scooters whose battery and connector are rated for it, but it adds heat, so stick to the original rating unless the manufacturer approves more.
Polarity and other symbols
Barrel-plug chargers often show a polarity diagram: a dot inside a C shape with + and − marks. "Center positive" means the pin inside the barrel is +. Most scooter chargers are center positive, but you must match the original. Reversed polarity can damage the battery management system.
Other marks: UL, ETL or CE show safety certification (look for UL in the US); a double square means double-insulated; a house symbol means indoor use only. There is also often a line about the LED: red = charging, green = full or not connected.