STIHL Australia has some tips on how the charging and care of 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, and
* Protect lithium-ion batteries from moisture, heat and cold.
What to be aware of charging lithium-ion batteries
1. Observe optimum temperatures when charging lithium-ion batteries
STIHL batteries can be charged within a temperature range of +5 to +40 degrees Celsius without any problems. Storage between -20 and +50 degrees is possible – although there will be functional losses at the top and bottom of this range. STIHL chargers offer additional safety: if a 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. Temperatures which are too high or too low can be harmful to the batteries – always observe the approved temperature range.
It is best to charge 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.
All STIHL batteries are delivered from the factory to retailers with a charge level of 30%. Even if a STIHL battery has been stored at a retailer for a long time, it is effectively protected against self-discharge.
How dangerous is it to charge a lithium-ion battery for too long?
It’s normal for a battery to warm up during charging, and there’s 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 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.
To prevent overcharging and excessive heat development, only lithium-ion cells that meet the highest safety requirements are installed in STIHL batteries, and 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 lithium-ion battery 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. Also, 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 per cent to three percent per year.
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.
Storage instructions for lithium-ion batteries
For optimum storage of STIHL lithium-ion batteries, STIHL recommends an ambient temperature of around 20 degrees.
In principle the batteries can be stored at between -20 and +50 degrees – however, there may be a loss of function and service life at the top and bottom of this range.
There’s plenty more great information on use and care of STIHL lithium-ion batteries at stihl.com.au.