Charging lithium-ion batteries

Overview on charging a lithium-ion battery

• Charge STIHL lithium-ion batteries to 80-100% before using them for the first time

• Safety technologies prevent lithium-ion batteries from overheating

• Worry-free overnight charging

• Protect lithium-ion batteries from moisture, heat and cold

What to be aware of when charging lithium-ion batteries

The assumption that batteries need to be fully charged after purchase no longer applies to advanced lithium-ion batteries. However, there are a few things you should keep in mind to ensure that your batteries have a long service life.

1. Observe optimum temperatures when charging lithium-ion batteries

You can charge STIHL batteries within a temperature range from +5 to +40 degrees Celsius without any problems. Storage between -20 and +50 degrees is possible – though there will be functional losses at the top and bottom of this range.

STIHL chargers offer you additional safety: If your battery is too warm after a long period of use, the charging process will only start once the battery has cooled to a certain temperature. 

 2. Avoid extreme temperatures for lithium-ion batteries

To protect and charge lithium-ion batteries correctly, they should not be placed on heaters. That’s because temperatures which are too high or too low can be harmful to the batteries – so you should always observe the approved temperature range.

It is best to charge lithium batteries at normal room temperature or at moderate outdoor temperatures.

3. Long charging processes are not required for lithium-ion batteries

Advanced lithium-ion batteries only require 80% charge before their first use – this takes between half an hour and four and a half hours, depending on the battery.

Does the temperature of a battery affect the amount of energy it provides?

One myth suggests that a battery should be placed on a heater during charging. This theory is based on the idea that electrical activity will increase as a result of the heat input, which should protect the battery during charging and extend its service life. Some claim it should even be possible to briefly reactivate a fully flat battery by heating it, on the grounds that only a warm battery can access its entire energy reserve. Now we know that not only is this theory incorrect, but the process is actually harmful to the battery.

During charging and discharging, the ions essentially migrate from one electrode to another – depending on the direction of current. If the battery is heated too much, the particles accelerate and the material decomposes – and service life is reduced as a result. In the worst-case scenario, easily combustible gases may be produced if the battery is strongly overheated. The battery will become unusable. In general, we recommend that you always observe the battery’s approved temperature range.

How dangerous is it to charge a lithium-ion battery for too long?

It is normal for a battery to warm up during charging, and there is no need to worry when this happens. STIHL high-quality batteries are protected against overheating and are basically risk-free. The charging process ends automatically once the battery is charged, meaning you don’t have to worry about charging a lithium-ion battery for too long. Imitations and non-OEM parts are more likely to pose a hazard, because these batteries can burst as a result of excessive heat formation.

If a battery exceeds its approved temperature range by a very large amount, this can cause a self-reinforcing exothermic chemical reaction called a “thermal runaway”. The heat generation within the battery becomes self-reinforcing, sparking a circular chain reaction which quickly melts the battery core. 

It is true that the risk of battery fire continues to be a matter of concern for many users. However, advanced STIHL batteries keep you on the safe side.

What advantages do products with lithium-ion batteries from STIHL offer?

The high-quality battery products from STIHL have many advantages, including low risk of fire from lithium-ion batteries, optimal protection against deep discharge, and temperature monitoring by means of an efficient battery management system. 

The highest safety standards for STIHL lithium-ion batteries

To prevent overcharging and excessive heat development, only lithium-ion cells that meet the highest safety requirements are installed in STIHL batteries.

Both batteries and chargers from STIHL are fitted with protective mechanisms that prevent overcharging and excessive heat generation.

Temperature monitoring by means of a battery management system

Each individual cell installed in a battery is monitored by a battery management system. This involves an integrated sensor which measures the temperature at the warmest point inside the battery – if the temperature is too high, the lithium-ion battery charging process is interrupted. 

Low fire hazard with lithium-ion batteries

With advanced lithium-ion batteries, the risk of fire is very low. This is ensured through various measures, one of which is the built-in battery management system that prevents overcharging and the associated high heat generation.

Optimum protection against deep discharge

The electronics in lithium-ion batteries automatically put batteries into an idle state if they are not used for a long period of time. This protects against damaging deep discharge.

Only low capacity loss

For all its battery products, STIHL uses advanced lithium-ion cells which do not need to be fully charged before first use and are ready for use within just a few hours. The reason for this is that self-discharge rates of STIHL batteries are vanishingly low – capacity loss is just one to three percent per year.

No memory effect

There is no memory effect with lithium-ion batteries. The memory effect refers to the permanent loss of capacity arising from partial discharge, which affects nickel-cadmium batteries (NiCd). The battery remembers the consumed energy requirement and over time only provides the previously used capacity instead of the original full amount. 

For optimum storage of our lithium-ion batteries, we recommend an ambient temperature of around 20 degrees. In principle you can store the batteries between -20 and +50 degrees – however, there may be a loss of function and service life at the top and bottom of this range. That’s why we recommend storing lithium-ion batteries correctly.

Full power with chargers from STIHL

Chargers such as the AL 300 quick charger actively help to cool the battery with the aid of a built-in air cooling system. Get to know our battery chargers:

The charge-level indicator on the STIHL battery

The four LEDs on the battery indicate the charge level, but can also indicate malfunctions in the power tool or battery. Just press the button on the battery to activate them. The LEDs will turn green for approximately five seconds and then show the charge level. If only one LED flashes green, this indicates low charge.

When the battery is plugged into the charger, the green LEDs also indicate the charge level (if no LEDs light up, the charging process is complete). If the LEDs light up or flash red instead, there is a fault:

^{The LED display of the battery provides information about the charge level or faults.}

More about STIHL battery power

If you would like to find out more about how a lithium-ion battery works and how STIHL makes the most of these functions, for example with intelligent systems, you can find out more in the Basic battery knowledge article.