Discharge cutoff voltage is a vital parameter concerning Lithium Battery lifetime. Therefore, this concept meaning should be made clear. Lithium battery here particularly refers to li-ion battery.
Lithium battery cutoff voltage means that it is not suitable to discharge any longer if lithium Battery Voltage reaches a certain value otherwise, partial capacity of lithium battery will be irreversible or even battery will be seriously damaged. Generally rated voltage of current single lithium battery is 3.7V and cutoff voltage 2.75V. Yet considering following two cases, manufacturers might raise cutoff voltage to 3.0V: one case is to use battery more safely; the other is relevant to specific electric devices and operating environment. Of course, on the contrary, producers may reduce cutoff voltage to 2.5V or 2.4V. There is no cutoff voltage less than 2.4V.
In case discharge operating temperature scope is -20~60℃, lithium batteries with 2.75V cutoff voltage is able to continue discharging, however discharge with voltage lower than 2.5V is not allowed because discharge loss between 2.75V to 2.5V might be partial but discharge lower than 2.5V will lead to serious damage to battery.
Lithium Battery Pack, often called multi-cell lithium batteries, also has cutoff voltage, which should not be less than 2.75*n (n is serial battery number). Take 6-cell lithium Battery Pack used on laptops for example, discharge cutoff voltage of this lithium battery with 3S2P combination is 2.75V*3=8.25V and 2.5V*3=7.5V is not allowed in practical use.
Actually, due to high lithium-ion battery price, both single lithium battery or multi-cell lithium battery are equipped with PCM or protection IC so that batteries will send a signal to electric devices in case of reaching cutoff voltage.
