A guide to proper lithium-ion battery storage
A guide to proper lithium-ion battery storage
Why you should not charge your lithium-ion battery before storing it
Today, battery technology uses lithium-ion as standard, and these cells experience negligible levels of self-discharge. To protect cells from over-discharge a lithium-ion battery is usually built with separate integrated fuses that can automatically switch a highly discharged battery to a rest state so they don't need to be fully charged before storage. In fact, lithium-ion battery life is extended if it goes into storage partly charged – that said, it’s worth remembering that cells are negatively impacted in the event of storage with a very low level of charge or if the battery is fully charged. We recommend that you store a lithium-ion battery with two lit LEDs, indicating a charge of 40-60%, to minimise ageing and self-discharge.
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Outdated battery technologies have high self-discharge
Older battery types such as nickel-cadmium batteries (NiCd) or lead batteries used in motor vehicles have high self-discharge rates, and so if a battery has not been used for a long time, it may be prone to over-discharge. This is when the battery charge level falls below the cut-off voltage. When this happens energy can no longer be supplied and the battery may fail to charge. That’s why battery care advice used to specify fully charging before any lengthy storage period, as well as regularly checking the remaining charge.
Cutting-edge lithium-ion battery technology protects against over-discharge
STIHL batteries rely on lithium-ion cells and feature exceptionally low self-discharge rates of just 1-3% per year of storage. In addition, all STIHL batteries include an intelligent battery management system known as BMS. This monitors the voltage in each cell integrated into a battery, and in doing so prevents over-discharge: if voltage in the lithium-ion battery cells falls too far, the battery automatically switches to rest state, and the discharge process is interrupted.
This also happens during lithium-ion battery storage and when unused for long periods, meaning that you no longer need to worry about your battery being damaged by over-discharge.
How To Store Lithium-Ion Batteries
As you’re probably aware, how you store lithium-ion batteries is extremely important from both a safety and efficiency perspective. If you don’t pay attention to the way that your batteries are stored in the short or long term, it can cause them to overheat and lead to a sensation known as thermal runaway.
To ensure you store your lithium-ion batteries safely and correctly, we explain the storage steps you need to take in detail below.
Temperature
The optimum storage temperature for lithium-ion batteries is 10C (50F). The higher the temperature at which your lithium-ion battery is stored, the more quickly it will self-discharge.
In most instances, temperatures below freezing won’t significantly damage lithium-ion batteries as they don’t contain water. Still, you shouldn’t store them at sub-zero temperatures regardless. If you’re storing your lithium-ion batteries long-term make sure the conditions are optimal.
Humidity
The optimum storage humidity for lithium-ion batteries is 50%. When the air is too humid, condensation can accumulate between the terminals, which can cause a short in the batteries.
In the worst-case scenario, a short can cause the battery to overheat and it may even catch fire. It’s for this reason that you should provide each terminal with a separate cover and do everything you can to prevent humidity from damaging the lithium-ion cells.
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Every battery self-discharges when it is stored in the long term. Typically, most lithium-ion batteries will self-discharge at around 5% in the first 24 hours of being charged. Thereafter, each battery will discharge at a rate of 1-2% per month. If your lithium-ion battery comes with a safety circuit, this alone will contribute to a self-discharge rate of around 3%. It’s best to store your lithium-ion batteries at around a 40-50% state of charge if you plan to use them immediately. You should also be mindful that lithium-ion batteries can suffer damage if you overcharge them for too long. When you check the charge of your lithium-ion battery, you need to remove it from storage and allow it to sit at room temperature for a couple of hours. You can then test it. If you find that your lithium-ion battery is showing heavy discharge, you will need to do the following: Trickle charge: (0.1C) until the cell voltage reaches 2.8 volts. If you don’t see this occur within an hour, your battery is probably damaged beyond repair. Fast charge: (1C) until the cell voltage reaches 4.2 volts. This should occur within 2 hours. Constant charge: until the charge current drops below 0.07C. If you keep store lithium-ion batteries in the right way, they can last for up to ten years, while those used within military and medical industries may even last twenty years. The crucial thing to remember when storing lithium-ion batteries is to regulate temperature and humidity while ensuring they’re at the right state of charge. If you have any questions about how to store your lithium-ion batteries correctly, or would like to place an order with us, get in touch via our website or give our Telford office a call on 01952 293 388. If you want to learn more, please visit our website Solar Lithium Battery Storage.Charge
Trickle, Fast, and Constant Charge
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