Lumicycle Li-Ion batteries

Li-Ion batteries can be damaged by being drained below a certain level, and can even become unstable, and so are usually protected by internal electronics which prevent the cells from draining too far. However, these electronics use a little current themselves, and may over the last six months have drained the battery below its minimum level, which is usually fatal and the battery should be replaced.

You should generally charge Li-Ion batteries to at least 50% before storing them for a long period.

The following may help to explain the problem (batteryuniversity.com) :

"Extreme low voltage must also be prevented. The safety circuit is designed to cut off the current path if the battery is inadvertently discharged below 2.50V/cell. At this voltage, most circuits render the battery unserviceable and a recharge on a regular charger is not possible.

There are several safeguards to prevent excessive discharge. The equipment protects the battery by cutting off when the cell reaches 2.7 to 3.0V/cell. Battery manufacturers ship the batteries with a 40% charge to allow some self-discharge during storage. Advanced batteries contain a wake-up feature in which the protection circuit only starts to draw current after the battery has been activated with a brief charge. This allows prolonged storage.

In spite of these preventive measures, over-discharge does occur. Advanced battery analyzers feature a 'boost' function that provides a gentle charge current to activate the safety circuit and re-energize the cells if discharged too deeply. A full charge and analysis follows.

If the cells have dwelled at 1.5V/cell and lower for a few days, however, a recharge should be avoided. Copper shunts may have formed inside the cells, leading a partial or total electrical short. The cell becomes unstable. Charging such a battery would cause excessive heat and safety could not be assured. "

Marv