How to store Lithium-ion batteries

Why you should not charge your lithium-ion battery before storing it

Today, battery technology uses lithium-ion as standard, and these cells experience negligible levels of self-discharge. To protect cells from over-discharge a lithium-ion battery is usually built with separate integrated fuses that can automatically switch a highly discharged battery to a rest state so they don't need to be fully charged before storage. In fact, lithium-ion battery life is extended if it goes into storage partly charged – that said, it’s worth remembering that cells are negatively impacted in the event of storage with a very low level of charge or if the battery is fully charged. We recommend that you store a lithium-ion battery with two lit LEDs, indicating a charge of 40-60%, to minimise ageing and self-discharge.

Outdated battery technologies have high self-discharge

Older battery types such as nickel-cadmium batteries (NiCd) or lead batteries used in motor vehicles have high self-discharge rates, and so if a battery has not been used for a long time, it may be prone to over-discharge. This is when the battery charge level falls below the cut-off voltage. When this happens energy can no longer be supplied and the battery may fail to charge. That’s why battery care advice used to specify fully charging before any lengthy storage period, as well as regularly checking the remaining charge.

Lithium-ion battery storage: cutting-edge technology protects against over-discharge

STIHL batteries rely on lithium-ion cells and feature exceptionally low self-discharge rates of just 1-3% per year of storage. In addition, all STIHL batteries include an intelligent battery management system known as BMS. This monitors the voltage in each cell integrated into a battery, and in doing so prevents over-discharge: if voltage in the lithium-ion battery cells falls too far, the battery automatically switches to rest state, and the discharge process is interrupted.

This also happens during lithium-ion battery storage and when unused for long periods, meaning that you no longer need to worry about your battery being damaged by over-discharge.

Proper storage of tools with an integrated battery

A power tool with integrated battery, such as those in the STIHL AI Battery System, needs to be treated differently from other cordless tools as you cannot remove the battery for storage purposes. Lithium-ion battery storage preparation for these tools is simple:

When is the best time to charge the integrated lithium-ion battery again?

If you are using your cordless power tool with integrated battery after a lengthy storage period, charge it just before you use it. This safeguards the capacity and has a positive effect on the service life. The battery will only charge at temperatures above 5°C; the charger monitors the battery temperature and prevents charging if the temperature is too low or too high.

Checklist: Lithium-ion battery storage

Every STIHL cordless power tool uses a cutting-edge lithium-ion battery because it is lightweight and quiet, but also offers high energy and power density. They have a long lifespan, but will need to be replaced eventually.

Keep your lithium-ion battery protected

• Remove the lithium-ion battery from your cordless power tool before storage. Check the charge level and make sure that 2 LEDs are lit on your battery. If required, use a damp cloth to clean dirt and soil off the battery.
• Store the battery in a dry place and out of direct sunlight, in a closed box for example.
• Temperature requirements: it’s best to store batteries at a temperature between -10°C and 50°C – dry basements, garages, or a well-insulated shed for example.
• Store your lithium-ion batteries in a secure place, and place them safely out of the reach of children.
• Store the charger separately from the battery, at a temperature between 5°C and 40°C.
• Further information on the storage temperature for your power tool is available in the instruction manual.

The optimal charge level for lithium-ion batteries storage

We recommend that you do not store STIHL batteries fully charged, but with two green LEDs – 40-60% charged. At this charge level the battery can stay unused in storage for two years with no damage, and with a minimal amount of self-discharge. You only need to charge your battery shortly before use. Batteries must always be charged at a temperature above 5°C.

Key considerations of lithium-ion battery storage

You do not necessarily need to charge lithium-ion batteries before storage – two LEDs should be lit when you put your lithium-ion battery away. It should also be stored in a dry place at a temperature between -10°C and +50°C. Outdoor storage is not recommended. Further information on the storage temperature for your power tool is available in the instruction manual.

Summary: lithium-ion battery storage

• Keep lithium-ion batteries protected from the elements during storage
• A STIHL lithium-ion battery should be 40-60% charged for storage, with two lit LEDs
• Lithium-ion batteries experience extremely low self-discharge even during long periods in storage
• Also be aware of the storage temperature for lithium-ion batteries: -10°C to 50°C is safe for your batteries. The precise storage temperatures for your cordless power tool are available in the instruction manual.