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I bought a battery for my laptop from a local store. When I inserted it into my laptop and tried to power it on, I noticed that it was deeply discharged. Then I connected charger and then it started charging. To check the battery state I powered it on and found out that battery percentage was zero. Then I left it for 2 hours and when I came back it was fully charged. Then I checked battery health statics and it was reported that battery is 100% healthy and has charged up to its nominal capacity.

Now I've these questions.

  1. Is this battery damaged due being stored in this state for a period of time? If so then why statics report that it's 100% healthy?

  2. What is the proper way to store li-ion batteries in warehouse as they have a self-discharge rate which leads to be fully discharged eventually even if they are 40% charged before storing them?

  3. Does storing battery unused in a warehouse, reduce its 2 - 3 years lifespan?

EDIT: I just checked one of my old laptops and figured out its battery was also 0% and now does not respond and doesn't recharge. Battery was detached and had been charged to 40% before being detached.

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    \$\begingroup\$ @winny Actually, OP cited correct preferred SOC for storing li-ion. \$\endgroup\$
    – Maple
    Commented Nov 4, 2020 at 21:24
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    \$\begingroup\$ I doubt the battery has been damaged. Keep in mind that whatever is reported by your laptop is done by software, which has its own logic and assumptions, not to mention bugs. According to this batteries will not discharge to 0 in any reasonable storage time, unless they have internal defects. As for warehouse storage, the self-discharge should probably be the lowest of your concerns, due to many regulations you must follow, like fire protection, temperature control etc. \$\endgroup\$
    – Maple
    Commented Nov 4, 2020 at 21:36
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    \$\begingroup\$ To answer your 3rd question, I don't think "lifespan" is used to describe battery usability. The drop in capacity is mostly due to charge/discharge cycles, and it seems manufacturers routinely sizing the batteries in their products to last for 2-3 years of typical operation, which is where this number comes from. \$\endgroup\$
    – Maple
    Commented Nov 4, 2020 at 21:44
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    \$\begingroup\$ @Maple there was no implication that the voltage was zero, merely that there was a little to no useful charge in the received condition. A "new" battery should not be received in deeply discharged condition; that hints it's either very very old stock or used or damaged. \$\endgroup\$
    – Chris Stratton
    Commented Nov 4, 2020 at 22:22
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    \$\begingroup\$ @ChrisStratton Without some kind of smart built-in BMS the only data available to software is a voltage. Regardless of what program considers to be fully discharged voltage, everything under it will be shown as "empty", even if it is only 0.01V below. So, you are right, it could be very old stock or damaged. But also it can be simply discharged just enough to register as 0%, while still not being "deeply discharged". I guess couple days of normal use should give a feel which one it is. \$\endgroup\$
    – Maple
    Commented Nov 4, 2020 at 23:16

2 Answers 2

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  1. 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 "deeply discharged" - 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

  2. 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)

  3. 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: graph

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  • \$\begingroup\$ Thanks but it's also been said that letting battery to reach 0% will damage battery. Now I'm wondering if it is damaged or not for being stored in this state in a while \$\endgroup\$
    – Nixmd
    Commented Nov 4, 2020 at 22:05
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    \$\begingroup\$ Batteries are designed to go to 0% of their designed capacity by definition. You might be confusing 0% capacity with 0 volts. Of course, any use of batteries would cause wear, so generally it's a choice between lifespan and performance/capacity. \$\endgroup\$
    – crossroad
    Commented Nov 4, 2020 at 22:07
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The problem wiht lithium ion cells is that the cell chemistry will be permanently damaged if the cell is deep discharged. If you want to know more about this, try searching for lithium plating or dendrite crystal formation which can damage the separator.

Don't mistake deep discharge with SOC 0%. This is just a value where the battery has reached the end of it designed capacity rating. A real deep dischrage condition is reached at a voltage below the minimal specified one in the cell datasheet.

It may still be possible to recharge the battery back to a normal voltage value but the usable cell capacity will most likely be reduced. The Probability of an internally damaged cell which can lead to fire or explosion is is too high so most of the commercial BMS systems (e.g. in electric cars) will mark the battery as permanently damaged.

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