Find out how to charge lithium-ion batteries correctly and what you need to be aware of.
12.03.2024
Charge STIHL lithium-ion batteries to 80-100% before using them for the first time
Safety technologies prevent lithium-ion batteries from overheating
Overnight charging of a lithium-ion battery is safe
Protect lithium-ion batteries from moisture, heat and cold
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.
Your STIHL Li-ion battery can be charged without a problem at temperatures between 5°C and 40°C. STIHL chargers also incorporate safety features so that if your battery is too hot when inserted into the charger after a long period of use, the charging process will only begin when it falls to an appropriate temperature.
Your Li-ion battery should not be placed on a heater for charging. Warming a charging battery does not save battery life and does not increase the capacity – in fact, the battery may be damaged if temperatures are too high or too low. Your Li-ion battery is best charged at normal room temperature or at moderate outdoor temperatures. We advise that you always check your battery’s permissible temperature range.
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.
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, ions move from one battery electrode to the other, depending on the direction of flow. If the battery is made too hot by the process, the particles accelerate and the material breaks down, leading to reduced battery life. If the battery overheats, in a worst-case scenario highly flammable gases may be released meaning that the battery becomes unusable.
We advise that you always check your battery’s permissible temperature range.
It's normal for a battery to warm up during charging, and is not a cause for concern. STIHL batteries are protected against overheating and are basically risk-free. When a battery reaches its full charging capacity, the charging process stops and the current is switched off. This prevents overcharging and the associated heat build-up.
If a battery exceeds its approved temperature range, it 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.
STIHL uses high-tech lithium-ion cells in all its cordless products. This technology has 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.
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.
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 charging process is interrupted.
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.
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.
All STIHL cordless products use advanced lithium-ion cells which do not need to be fully charged before first use and are ready for use within a few hours. In a year, a STIHL Li-ion battery loses just 1-3% of capacity via self-discharge.
The memory effect describes the permanent loss of capacity that nickel cadmium batteries are affected by. Repeated partial charging reduces the amount of power the battery makes available, as it only “remembers” the most recently added amount of energy, rather than its full capacity. The advent of the Li-ion battery means this issue with partial charging is a thing of the past.
If a battery runs hot
Electrical safeguards in the battery, charger and power tool prevent overheating, automatically switching off functions at critical points. In the unlikely event of overheating, all battery cells are protected by robust and flame-retardant housing.
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.
The four LEDs on a STIHL Li-ion battery communicate the charge level, but can also indicate a malfunction on the power tool or battery. Press the button on the battery and the LEDs will light up green for around five seconds, then indicate the charge level. If only one LED flashes green, the battery level is low.
The green LEDs also indicate the charge level while the Li-ion battery is charging (if no LEDs are lit, the charging process is complete). If the LEDs are lit up or flashing red during charging, a malfunction has occurred.
LED display | Meaning |
|---|---|
 | The battery should be charged. |
 | The battery is 20-40% charged. |
 | The battery is 40-60% charged. |
 | The battery is 60-80% charged. |
 | The battery is 80-100% charged. |
 | The battery is too hot or cold. |
 | The power tool is too hot. |
 | There is a fault in the power tool. |
 | The battery has a fault. |
The LED display of the battery provides information about the charge level or faults.
How long a battery needs to charge depends on its capacity. In most cases, charging to 80% takes between half an hour and four and a half hours. The battery can be used without any problems at this charge level, even the first time it is used. Charging to 100% takes a little longer, with the exact time depending on the type of battery.
Whether lithium-ion batteries can be charged with a standard charger depends on the battery. Specific connections are often needed to charge a lithium-ion battery. This is generally related to the products in which the batteries are used. So a suitable charger is required for charging.
There are three points to ensure correct charging of a lithium-ion battery. First, the temperature should be between +5 and +40 degrees Celsius. Make sure that the battery is protected from moisture. Secondly, connect it to the appropriate charger. Advanced safety technologies in STIHL lithium-ion batteries protect against overheating and automatically regulate the flow of current. And lastly, before using the battery for the first time, you should charge it to 80-100%.
It is often assumed that the battery temperature has an impact on the amount of energy it provides. According to this theory, electrical activity should increase due to heat input. Some claim it should even be possible to reactivate a fully discharged battery by heating it up. Today this theory is known to be incorrect, and heating a battery – on a heater for example – actually damages the battery.
When charging a lithium-ion battery, temperatures should be between +5 and +40 degrees Celsius.
Charging a battery for too long is potentially dangerous if using imitations and non-OEM parts. Quality batteries are generally protected against overheating, though defects can never be entirely ruled out.
