I bought a Li-ion battery which was deeply discharged, now what?
I've heard that low current pulses over the course of days could be a good approach to bring back deeply discharged batteries. As other people have pointed out, 0% capacity is most likely not 0 volts, and usually does not count as being &quot;deeply discharged&quot; - batteries operate between a range of voltages, for lithium cells it's generally 4.2 volts full and about 2.8 or 3 volts as empty. TLDR 0% does not necessarily mean deep discharge

Additionally, some recommend leaving batteries at 75% to 50% of their operational voltage range for long term storage to reduce chemical stress. The self discharge rate curve flattens out as the voltage decreases, so this is further beneficial. (see graph)

Generally speaking no. The main determiner of lifespan is charge and discharge cycles. (number quoted on datasheets generally mean full charge and full discharge, batteries last a lot longer if their voltage don't swing as far so its preferable to charge to a lower voltage and charge more often)


Here's a graphic comparing self discharge rate in cells of various condition from batteryuniversity: