How Should Your Lithium Batteries Be Stored

Apr 09, 2021 | XTAR

Lithium batteries have long been widely used in various industries. When using lithium batteries, the most important thing is the maintenance and safety of the battery itself. Because if storage and maintenance are not good, the battery may be damaged, and cause accidents such as fire and explosion. I know some of you have tons of old batteries torn from laptop, electric bike etc. You may only use 2-4 batteries in daily life, and store the rest for a long time.

Then, how to properly store the lithium battery?

If you plan to not use your lithium batteries for a long time, then you should recharge them every 3 to 6 months, that is, charged to a voltage of 3.5 to 3.8V and maintained at a power level of about 40%-70%. It is not suitable to be fully charged. The battery should be stored in a dry environment at around 15°C or in moisture-proof packaging. Keep away from heat sources, and don’t place it in direct sunlight.

If they are protected batteries, recharge them every 3 months would be better, because the protection board also will discharge some power.

Why should charge to voltage of 3.5-3.8V and power of 40%-70%?

Chemical substances are more active at high voltage and high temperatures, and are prone to some bad reactions, which appear as capacity loss in the battery.

When a lithium battery is fully charged, about 90% of the lithium is concentrated on the positive electrode, and the remaining 10% is responsible for maintaining the stability of the negative electrode structure. When the battery is charged to 4.35V or more, all the lithium ran to the positive electrode, and then the battery is not far from death.  

So if the battery is stored empty however it can be drained too much, and lithium ends to age quicker if it stored while it’s full.

When the battery is 40%, the number of lithium ions on both sides of the positive and negative electrodes is basically balanced, and both sides are in a relatively stable state.

How to recharge your lithium batteries every 3 months?

We do that for the purpose of supplement the battery’s self-discharge loss. Just fully charge, then discharge, and then recharge it to around 40%-70% state.

Can the newly purchased lithium battery be stored for a long time if it is not used? 

Actually your newly bought lithium battery is not fully charged. If the lithium-ion battery is shipped at 100% power, it will bring risks during transportation or storage, because when fully charged, lithium-ion is the most active, and the safety hazard is also the biggest.  According to the measured data of most battery factories, shipping with around 50% of the power can guarantee its storage for more than one year, the voltage is still above 3.2V, and the recovery capacity is above 98%. But you can’t sure when you get it, how long has the battery been already stored. You’d better to detect the voltage and power of the battery firstly and then recharge it before storage.

How long can the lithium battery be stored when it is fully charged?

Don’t take too long. Lithium batteries will permanently lose capacity if stored for a long time. The charged power and storage temperature of the lithium battery will affect the capacity of the lithium battery. Someone had a test for it. He tested the remaining capacity of the lithium battery after one year of storage under different temperatures and battery states. Let’s see the test data below.

Storage Temp.     40% state of charge        100% state of charge

zero degree                    98%                                  94%

25 degree                       96%                                  80%

40 degree                       85%                                  65%

60 degree                       75%                                  60%

It can be seen that the higher the storage temperature and the more fully charged the battery, the more severe its capacity loss. Therefore, it is not recommended to store lithium-ion batteries for a long time. If users have idle batteries, the storage conditions recommended are 40% state of charge and storage temperature below 15 degrees or lower. The battery is generally stored for about 3 years, when not in use. And some articles said if storage in fully charged over one year, the capacity will has a over 10% of irreversible loss.

How to adjust the battery to a best storage state?

If your charger does not have the function of storage mode, you have to keep an eye on the charging and discharging of the charger, calculate the required time, or discharge it in a flashlight and other equipment for a period of time. It is really inconvenient. In this situation, XTAR developed two chargers – XTAR VC8 and XTAR VC4S, which have storage function. You only need to install your batteries in the charger, and choose the storage mode. Then the charger will adjust the voltage of your batteries to the best storage state.

In order to prelong your battery life, please pay attention to its storage, especially for the guys who have lots of stored batteries and like DIYs.


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