What are the possible reasons for zero voltage or low voltage?

1. When batteries are short circuit from outside or over discharged/over charged or charge reverse.
2. When battery is continuously charged with high current, the electrode swells so that the two electrodes contact directly, short circuit is caused.
3. Batteries are short circuit or slightly short circuit from inside. Ex. There is spur on positive electrode or negative electrode, which gets through the insulator causing short circuit; Positive electrode and negative electrode are placed inappropriately and electrodes contact each other, causing short circuit; Positive electrodes contact directly with steel case, causing short circuit; Powder on negative electrode drops into the insulator or insulator fails to work well so that positive plates contact negative plates, causing short circuit.