Many people have developed a bad habit of leaving their electric bike batteries on the bike when they are away, without turning off the air switch, and not riding for several months. When they come back to ride after several months, they find the bike has no power, and the battery cannot be charged. Even if they plug in the charger for 24 hours, the indicator light remains green. This is because the battery voltage is too low, and if the voltage difference between the battery and the charger output is too large, the charger cannot deliver the charge to the battery.