Storing batteries properly over winter: what you should know

Maurice Forgeng, Epoch Times

In brief:

• Proper winter storage is important for the longevity of batteries.
• Besides e-bikes, electric garden tools and all cordless power tools are affected.
• Damage shows itself in some cases on the outside, in others only during charging or operation.
• To prevent fires, charging should as far as possible not take place unattended.

The approaching winter with its low temperatures poses challenges not only for us humans. The batteries in many household and garden appliances are also sensitive to cold. Cold does not automatically damage a working battery. But it can temporarily reduce its performance and usable capacity. Anyone who is sending their battery-powered devices into a longer winter break should think carefully about whether the unheated shed in the garden or yard is a suitable place. Besides the right storage location, the right charge level matters too. Dryness should likewise be ensured.

Which devices are affected?

Besides the e-bike, you should also think of the e-scooter in the garage and the electric lawnmower in the garden shed. Many homeowners also have battery-powered garden tools such as hedge trimmers, leaf blowers, chainsaws or strimmers. Anyone with an unheated workshop should also think of their cordless tools such as drills, jigsaws or screwdrivers. But battery storage systems standing outdoors, such as those of balcony power plants, are affected too. In the hobby sector, drones and their remote controls as well as cameras now often belong here as well. Not to be forgotten are larger battery systems in motorhomes or boats.

What to bear in mind for winter storage

If a battery can easily be removed from the device, the owner can simply bring it into an area protected from the cold. If a battery is permanently installed in the device, however, the entire device should if possible spend the winter in a suitable place. It is also advisable to look at the manufacturer’s instructions on winter storage, if available. In the worst case, incorrect storage can become expensive if it damages the battery. If a battery has to be replaced, additional costs usually arise. If it is the battery of an e-bike, a replacement battery quickly costs several hundred euros, in some cases over 1,000 euros.

The right climate

According to the motoring club ADAC, the decisive factor for the storage location is first of all the right climate. Batteries should accordingly be stored at temperatures between 10 and 20 degrees Celsius and in as dry a environment as possible. Direct sunlight should also be avoided, as it can heat up the energy stores and thereby likewise cause damage.

These precautions apply especially to batteries with lithium-ion (Li-ion) technology. They are the most widespread and are used in almost all modern vehicles, tools and garden appliances. In addition, there are lithium iron phosphate batteries (LiFePO4), which are used in solar systems and various electric vehicles, as well as nickel-metal hydride batteries (NiMH). The latter cell chemistry is also used by the familiar AA/AAA batteries that power small devices.

Keeping the right charge level

For optimal winter storage, the charge level of the battery should also be in the correct range. What this means in an individual case can differ from manufacturer to manufacturer. In general, batteries should be stored neither completely full nor empty for a longer period. A medium charge level of around 40 to 60 per cent is most suitable.

The self-discharge of batteries over time must also be taken into account. Even though it is low in lithium-ion batteries, so-called deep discharge can occur during longer periods of rest. If this happens, the battery often can no longer be charged properly afterwards and has to be replaced. To avoid this, the owner should regularly check the charge level of the stored batteries and recharge them if necessary. In addition, the ADAC recommends following the respective manufacturer’s instructions on longer-term storage of the battery. If the owner wants to use the battery again after the winter, it should be fully charged before use.

Spotting damage quickly

If a battery is defective because of incorrect winter storage, there are in individual cases several ways to detect the damage. Sometimes a simple look is enough, if the battery is swollen. This points to gas formation inside. Any further use is to be avoided: there is a risk of fire and explosion. Such a battery – if it is still in the device and can be removed – should be removed immediately, stored separately and disposed of properly. The same applies if cracks appear in the battery. In some cases, however, a defect only becomes apparent during charging or use in the device. Signs of this can be overheating, longer charging times, loss of capacity, sudden switching off, an inaccurate battery indicator or too low a voltage.

If the battery continues to be used in winter

Not all devices with a battery go into winter hibernation. Many people continue to use their e-bike or e-scooter in winter. In doing so, the battery can be directly exposed to icy temperatures. To avoid impairment or even damage from the cold, it is therefore advisable to first let the battery slowly come up to room temperature after the ride. Afterwards it can be recharged. This should be avoided at temperatures below 0 degrees. Electric cars in some cases have an internal battery heater for this.

Fire risk exists

Batteries also represent a cause of fires. Owing to their wide use, lithium-ion batteries are now the most frequent cause of fires caused by electricity. Ignition often occurs during charging.

The Institute for Damage Prevention and Damage Research of the public insurers (IFS) therefore advises not to charge these batteries unattended where possible. A smoke detector in the room in which the battery is charged is also advisable. If it sounds the alarm, someone must react and be able to extinguish the fire at an early stage.

The fire risk with lithium-ion batteries lies in their strength: the high energy density compared with other types of battery. This makes them more sensitive. Under excessive loads or in the event of a defect, they can go into thermal runaway. In this case the battery releases the stored energy suddenly in a violent reaction – ignition occurs. The good news is that ignitions occur comparatively rarely. The damage mentioned occurs far more frequently with incorrect storage over the winter months. Anyone who takes the winter storage tips given in this article into account therefore has a good chance of reviving their batteries in spring without complications.

This article first appeared in German on Epoch Times – with kind permission of Maurice Forgeng.
Cover image: Ralphs_Fotos / Pixabay