Question:

We want to know how long the rechargeable Li-on battery will last if left plugged-in in the new light, so that we could tell user a reasonable life time for the battery. We know you offer one year warranty for the battery. For our current moodels, we tell user the life time of the battery could be 3 to 5 years.

About the actual life time of the battery:

1) First of all, my company provide a one-year battery warranty, which does not mean that the battery life time is only one year. Battery is a consumable part of the product, its service life depends on the daily use and maintenance of the battery in addition to the time factor. In practical application, the battery service life of many products is far more than one year.

The service life of the rechargeable battery used in our products mainly depends on the number of charging and discharging cycles, secondly the working hours.

Taking 3.7V lithium-ion battery as an example, the designed working life of the battery is more than 500 charging and discharging cycles:

A1) Assuming that the battery is charged and discharged 50 times a year, the theoretical service life of the battery is 10 years. However, this is the theoretical result after all. In practical application, the actual service life will be about 3 to 5 years due to the deterioration characteristics of the internal chemical composition of the battery, as well as the working environment and other factors.

A2) Assuming that the battery is charged and discharged 500 times a year, the theoretical service life of the battery is only 1 year. In practical application, this high-frequency charge discharge cycle belongs to the high-intensity working mode, which will cause the rapid deterioration of the internal chemical composition of the battery and the corresponding reduction of the battery capacitance. After one year's use, the internal capacitance of the battery may be only 30% to 40% of the initial capacity, and the subsequent work effect is greatly reduced. In this case, we suggest that the customer should replace the battery in time.

A3) In addition to the number of charges and discharges, the depth of each discharge will also affect the working life of the battery. For example, when a battery is discharged to 50% of its initial capacity, it will start charging immediately, which is different from that when it is discharged to 100% (i.e. deep discharge), and then it will start charging. In these two working modes, the working life of the battery is also greatly different.

A4) Take the United States and Canada as examples, both countries are well-developed countries, the local power grid construction is relatively perfect. In the last 10 years, there are few long-term power outages at a single location, which is similar to the situation in A1. Therefore, excluding human factors, the number of automatic emergency lights per year is very small in a natural state, the actual service life of an emergency light is very likely to be three to five years, or even longer.

This is also in line with the actual performance of our products in the market at present. In the local buildings in the United States and Canada, we can often find some old emergency light products produced by our company. According to the model and appearance of the products, we can judge that many lamps have been working for more than 5 years. When we press the test switch on the lamp, the lamp can still light up automatically and work normally.

All in all, the service life of the battery is determined by the user and cannot be generalized.

If it's just for consumers' questions, give a reasonable explanation, not an official warranty period，can tell consumers that under normal working conditions, the battery's possible working life is between 3 and 5 years.