I bought an electric car and charged it every three days. I think the battery is dead. What is the reason?

It's not the battery. Batteries actually convert chemical energy into electrical energy. When it is cold, the activity of the battery active material becomes worse, and the discharge capacity decreases at room temperature, which is normal. Solution: 1, try to charge indoors (high indoor temperature); 2. Try to charge the battery below 50%; 3; Replace lead-acid batteries with lithium batteries or other batteries with low and low temperature effects.