I bought a TRIANGLE 48v Panasonic GA 18650 17.5ah Pack HIGH POWER + LONG RANGE with 48V Advanced Luna 300W Ebike Charger on 1/16/2018.

The charger says 54.4 volts, but the battery is either not charging or holding the charge. The battery shows only 4 - 5 volts. I have had multiple problems with my bike over the past year, so I have not ridden it much or used the battery much. I only charged the battery about 20 times at most since purchase. It did sit out in my garage for about a month without the charger hooked up during a cold spell this winter. Could that have killed the battery? I am wondering what can account for the battery not performing at this time? Or could it be the battery charger?