Dead Battery Voltage and its Charging

1. How can we say a battery,say Li-ion battery, is dead when it is 2.8V itself instead of 0V? How can the 2.8V not give current? What is happening? This question, is applicable to all other batteries also. Why do we say a battery is dead when it is not completely 0V, but when it is hanging some very around 2.8V for Lithium ion and 1.1V for the AA battery whose nominal voltage is 1.5V and others?

2. I have a Li-ion battery which I tried to charge. The maximum voltage mentioned in the battery is 4.4V max. And its nominal voltage is 3.85V. But, when I connect the battery to the USB Charger to charge the dead battery which was at 2.8V, the voltage line reads 4.6V. How is the 4.6V obtained and won't the battery get damaged as we are feeding 4.6V which is more than its maximum 4.4V voltage which is mentioned?

• 1) different batteries have different chemistry and you seem to ask this without even trying to do own research, there is plenty material about this subject 2) In you other question you already have an answer to that, there is a charger chip between supply input and battery. Please don't ask same question in multiple places before getting an answer. Jun 15, 2020 at 8:56
• Does this answer your question? Battery Discharged - But Potential difference exists without any current flow Jun 15, 2020 at 9:03
• No. I am not clear on why you call a battery dead when it has some voltage left in it? And is that voltage not capable to provide current? Can someone provide a real example of a battery that will not work because it has less voltage (the dead condition, even if it has some voltage left) Jun 15, 2020 at 9:56
• A dead battery is one that can't be successfully recharged to provide a useful battery with broadly the same energy capacity as a new battery. 2.8 volts is not a dead battery exactly but you shouldn't use it as a power source because as soon as the voltage drops to something closer to 2.5 volts, it will be unusable and non-re-chargeable. Then it can be regarded as dead. Jun 15, 2020 at 11:03