Use a thick extension cord for battery chargers.

Yes, you can, but a cheap or overly long cord will slow your charger down.

Battery chargers for power tools pull a decent amount of current, especially fast chargers. A long, thin extension cord (like a 16-gauge light-duty cord) introduces resistance and drops voltage. The charger sees less voltage and either takes longer to deliver full power or throttles itself to protect the battery.

For a cord under 25 feet, 14-gauge is fine. For 50 feet, go with 12-gauge. Anything longer than that or running a high-amp charger (like for a big lawn mower battery) — stick to 10-gauge or don’t use an extension at all.

You won’t damage the charger or battery, but you’ll definitely waste time. Get a decent, heavy cord once and stop wondering.