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Lithium-ion batteries, also known as Li-ion batteries, reliably supply various end devices with power, the spectrum of applications ranging from smartphones to cordless screwdrivers to pallet trucks and forklifts. To ensure that these batteries remain powerful for as long as possible, it is not only important to charge the lithium-ion batteries correctly, but also to ensure they are stored properly. In our guide, you can learn the best ways to store a lithium-ion battery, how to reduce risk of fire and how to prevent damage to batteries even during longer storage periods.
Fire hazards when storing Li-ion batteries
There are many advantages that lithium-ion batteries offer in comparison to conventional batteries: they are enormously powerful, have comparatively short charging cycles, and there is no memory effect if used correctly. Li-ion batteries differ from lithium metal batteries in the fact that the latter are not rechargeable and can be used to power devices such as wristwatches, for example.
Improper storage of lithium-ion batteries in a warehouse or other location can lead to dangerous fires, even if there are protection measures built into the battery. The reason for this is the electrochemical construction of lithium-ion batteries, which consists of several components, each of which has certain chemical properties. The lithium contained in these batteries is particularly reactive: it reacts violently to contact with water and is unstable at high ambient temperatures.
If the ambient temperature is too high, flammable gases can form inside the batteries due to chemical processes. From a cell temperature of 70° Celsius, a thermal runaway can occur, causing the battery to ignite and burn. This effect is intensified by a high number of interconnected battery packs. Although these are very powerful, they are also particularly susceptible to a thermal runaway. If only one battery cell in the group overheats, the neighbouring cells can also overheat, causing a chain reaction and an uncontrolled fire as a result.
The greater the power of a Li-ion battery, the more battery cells required and the greater the risk of fire. Particularly powerful batteries, such as those used in pallet trucks or stacker trucks are therefore more prone to fire hazards than accumulators with lower performance, which is why safe storage is so important.
Storing lithium-ion batteries safely: What to look out for
To ensure battery units last as long as possible and to prevent storage damage or fires, you should observe the following points when it comes to the safe storage of lithium-ion batteries:
- Choose a cool and dry place for lithium-ion battery storage
To prevent the batteries from overheating during storage, they should be stored at temperatures between 6 and 15 degrees Celsius. This means that cellars, cold rooms or refrigerators are highly suitable – but only if they are dry.
The same applies to contact with water: if the lithium inside the battery comes into contact with water, the heat generated by the chemical reaction caused can lead to the formation of toxic lye and flammable hydrogen. If you want to store lithium-ion batteries in the fridge for fire protection, you should therefore store them in waterproof packaging to ensure that any water – including condensation – cannot penetrate the battery. - Store a lithium-ion battery separately from its device
To avoid chemical reactions caused by leaking coolant, lubricant or brake fluid and to prevent damage to the unit in case of fire, lithium-ion batteries should be removed from the electrical appliances they operate and stored separately. If a battery is permanently installed in a device, it must be checked for leaks, loose cables and other damage before being put into storage.
- Protection against mechanical damage
To ensure safety when lithium-ion batteries are in storage, you must ensure that fire protection against internal and external short circuits is provided. Make sure that the lithium-ion batteries are not exposed enough to be hit accidentally and prevent mechanical damage by counteracting a short circuit of the battery poles with appropriate pole protection caps.
- Avoid high temperatures
Avoid storing the Li-ion batteries in a place prone to sudden or permanently high temperatures. The batteries should also be protected from direct sunlight.
• If no automatic extinguishing systems are installed in the storage rooms, the lithium batteries must be stored at least 2.5 metres away from other flammable stored goods.
• Damaged or defective batteries should be stored in specialised safety containers, and until you can properly dispose of lithium-ion batteries, you should store them in a separate area. - Store lithium-ion batteries with half charge
It is not recommended that a lithium-ion battery be put into storage empty, but rather at a charge capacity of 50 to 70 percent. This prevents a deep discharge, which can have a negative effect on battery performance, shorten service life or even cause the Li-ion battery to stop functioning.
- Check the charge level regularly
If you store a lithium-ion battery for a longer period, the charge level should be checked at regular intervals. Topping up the battery charge at intervals of 3 to 4 months can be useful in protecting the battery from deep discharge.
- Observe the manufacturer’s instructions
For the safe storage of lithium-ion batteries, it is always advised to follow the manufacturer’s instructions and product data sheet notes that come with each unit.
Hazard classes determine the storage of lithium-ion batteries
There are no public UK regulations on the storage of lithium-ion batteries, however, it is still recommended that they be treated and stored as a hazardous material.
According to UK regulations on hazardous material storage, lithium-ion and lithium-polymer batteries must be stored in appropriate hazardous materials cabinets and containers. This goes, not only for the storage, but also the transport of lithium batteries, as under transport regulations they are officially recognised as Class 9 hazardous goods. Safety cabinets should be in accordance with BS EN 14470 and container and transport systems should be ADR-compliant with a fire protection function.
General storage and transport regulations also differ depending on battery performance classification (low, medium and high performance) and there are different hazard classes for lithium-ion and lithium-metal batteries, which further determine storage requirements. As there are no significant differences in the storage requirements for lithium-polymer batteries and lithium-ion batteries, the same regulations apply to them in the following overview:
| Power | Symbol | Lithium metal battery (UN 3090) | Lithium-ion battery (UN 3480) |
|---|---|---|---|
| low* |  | < 2 g Li per battery | < 100 Wh per battery |
| medium** |  | > 2 g Li per battery and < 12 kg per battery | > 100 Wh per battery and < 12 kg per battery |
| high*** | | > 2 g Li per battery and > 12 kg per battery | > 100 Wh per battery and > 12 kg per battery |
*Low power: General UK safety regulations apply to lithium-ion batteries in this class. If lithium-ion batteries or lithium-metal batteries are stored in larger quantities (volumes over 7m3), the regulations for medium power batteries apply.
**Medium power: Here, the focus is primarily on fire protection. Lithium batteries in this classification must be stored at least 5m away from other warehouse storage areas, especially areas housing materials that are particularly flammable. In addition, storage areas must be equipped with a fire alarm system that has a connection to a permanently manned office. Fire extinguishing systems and extinguishing agents must be provided in accordance with the manufacturer’s instructions. For storage volumes covering an area of more than 60m2 or more than 3m in height, the provisions for high-power lithium batteries apply.
***High power: There arecurrently no concrete UK safety regulations for the storage of high-power lithium-ion batteries. Protective measures for these types of batteries are usually made in agreement with the property insurance firm covering the location where the batteries are stored. In principle, the specifications for medium power batteries should be complied with. Other measures, such as separation and quantity limits for the storage of high-power lithium batteries are recommended to provide additional safety.
FAQ on the storage of lithium-ion batteries
How long you can store lithium-ion batteries depends largely on the conditions of storage. Compared to nickel-cadmium batteries, for example, whose self-discharge rate of 10 to 15 per cent is much higher than that of lithium-ion batteries, Li-ion batteries are relatively easy to care for and can be stored for a long time.
If you follow the instructions described above, modern accumulators can be stored undamaged for several years with continuous operation.
Modern lithium-ion batteries tend to self-discharge even when not in use. This is usually 1% per month, but it can be higher depending on the temperature and humidity of the storage environment. Permanent self-discharge can lead to deep discharge which can damage or even destroy the battery.
Deep discharge occurs when the power level falls below the discharge voltage, i.e. the battery capacity is completely exhausted. For lithium-ion batteries, this voltage is 2.5 volts. If the proper storage of lithium-ion batteries is not adhered to and the battery becomes deeply discharged, it may affect performance in the long term or even cause the battery to become unusable.
The following points should be observed for the safe storage of lithium-ion batteries:
• Choose a dry place
• Avoid high or fluctuating temperatures
• Store Li-ion batteries at a charge level of about 50 to 70%
• Check the loading capacity regularly
• Protect lithium-ion batteries from mechanical damage
• Store batteries separately from their operational device
• Observe the manufacturer’s instructions and product data sheet
Proper and safe storage of lithium-ion batteries is important as it ensures durability, continuous performance and avoids the risk of dangerous fires and damage to the battery.
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