What is a lithium-iron battery?
Lithium-iron batteries (LiFePO4 or LFP) are rapidly becoming the preferred choice for various applications due to their lightweight design and high energy density. Typically, these batteries consist of multiple LiFePO4 cells with integrated circuit boards that protect the cells.
Each cell consists of a cathode, anode, diaphragm, electrolyte, and two collectors (positive and negative). The anode and cathode are responsible for storing lithium, while the electrolyte facilitates the movement of positively charged lithium ions through the diaphragm between the anode and cathode. This charge movement creates a voltage that allows current to flow from the positive electrode to your application and back to the negative electrode.
How do I care for my lithium batteries?
Rechargeable Li-Fe batteries have a limited life span and their ability to store power diminishes over time. Once the battery capacity is reduced, it cannot be restored. Therefore, proper care and maintenance of lithium batteries is critical.
LiFePO4 batteries can withstand up to 2,000 full charge cycles or up to 6,000 partial charge cycles, depending on use! A full charge cycle consists of discharging the battery from a fully charged state to fully discharged and then fully charged again. Prolonged periods of unused batteries may affect their service life or even lead to failure.
To maintain battery capacity, it is recommended that all unused lithium batteries and battery cells undergo a complete maintenance cycle (charge to 100% State of Charge (SoC), discharge to 100% Depth of Discharge (DoD), and recharge to 50% SoC) at least once every 6 to 12 months. Periodically check batteries and battery packs to ensure that their open circuit voltage (OCV) is sufficiently high. Use the table below to determine the recommended minimum storage voltage. If the voltage falls below this value during a maintenance check, it is recommended that the battery be charged to the top of the specified voltage range.
| Voltage Range (V) | Lithium Iron Phosphate Product Type |
|---|---|
| 3.3-3.4 | Individual batteries |
| 13.2-13.6 | 12 Volt Battery Pack |
| 26.4-27.2 | 24 Volt Battery Pack |
| 52.8-54.4 | 48 Volt Battery |
When checking the voltage of a cell or battery pack every six months, also check for terminal corrosion and case integrity. Do not use any damaged cells or batteries.
LiFePO4 batteries will continue to slowly self-discharge during storage, regardless of how you maintain and store them. If your battery has Bluetooth capability, the self-discharge rate may be higher due to the power consumption of the Bluetooth module. Regularly checking your battery’s charge level will help keep it in a healthy state and ensure that it provides more power for your applications.
An easy way to check the health of your battery at home is to monitor the runtime of your apps. When purchasing a new lithium battery, take note of the runtime it provides. As the battery ages, the initial runtime will serve as a baseline for comparison to help you assess the battery’s health. Runtimes may vary depending on the applications and configurations you use.
For more detailed information on maintaining and selecting the right Li-Ion battery, our Li-Ion Battery Selection Guide may be helpful.
How do I charge my LiFePO4 battery?
Using a dedicated charger for lithium-ion batteries is the best charging method to ensure that the charging cycle is completed every time. Cohen’s Li-FePO4 chargers utilize an intelligent 3-step charging logic to efficiently charge even deeply discharged batteries.
Performance and battery life
Can a lead acid charger charge a lithium battery?
There are significant similarities between the charging curves of sealed lead acid (SLA) and lithium batteries. However, care must be taken when using SLA chargers with lithium batteries as they may damage, undercharge or reduce the capacity of lithium batteries over time. For a more in-depth look, see our blog post, “Can I Charge a Lithium Battery with a Regular Charger? , which provides more insight into using SLA chargers for LiPo batteries.
The open-circuit voltage (OCV) of a fully charged 12V SLA battery is approximately 13.1 V, whereas the OCV of a 12V LiPo battery is approximately 13.6 V. Damage will only occur if the charging voltage significantly exceeds the battery’s fully charged voltage.
For SLA batteries, the charging voltage should be kept below 14.7V during the bulk charging phase and below 15V for lithium batteries. Float charging is only applicable to SLA batteries, usually around 13.8V. Therefore, a charging voltage range of 13.8V to 14.7V is sufficient to safely charge both types of batteries without causing damage. When choosing a charger, it is vital to ensure its operating voltage is above range.
What charging rate extends the life of lithium batteries?
Choosing the right charger requires an understanding of the charge rate in relation to battery capacity. Lithium batteries can be charged at a rate of up to 1C (equal to their capacity), while lead-acid batteries should be charged at a rate of less than C/3 (one-third of their capacity). For example, a charge rate of 10 amps applies to a lithium battery at 10 amps, while a charge rate of 10 amps applies to a lead-acid battery at 10 amps.
In order to prolong the service life of Li-ion batteries and, at the same time, to meet the demand for fast charging, it is recommended that the charging rate of Li-Iron Phosphate batteries should not be lower than C/4 nor higher than C/2. Taking 10Ah batteries as an example, the charging rate should be between 2.5A and 5.0A, with 2.5A being the best choice. If you must choose between a 2A charger and a 5A charger, the 2A charger is preferable. Although a 5A charger takes about 2 hours to charge fully, it may shorten battery life. Conversely, a 2A charger takes about 5 hours to charge fully and maximizes battery life.
Charge cutoff currents are typically 2.5-5.0% of the battery capacity, i.e., for the batteries described above, the cutoff current is 0.25-0.50 A. Typically, the charger determines the current cutoff setting, so manually adjusting it is unnecessary to ensure optimal battery life.
Universal chargers often have a feature that selects the battery chemistry, which is an excellent way to extend battery life. This feature automatically adjusts the optimal voltage range for charging and recognizes when the battery is fully charged. For lithium batteries, the charger automatically shuts off, while for SLA batteries, the charger automatically switches to float mode.
Long-term storage
When storing batteries for extended periods of time, the different storage requirements of SLA and lithium batteries must be considered.
The chemistry of the battery determines its ideal State of Charge (SoC) for storage; SLA batteries should be kept as close to 100% SoC as possible to prevent sulfation, which can lead to the formation of sulfate crystals on the lead plates, ultimately reducing the capacity of the battery.
In contrast, lithium batteries should be maintained at approximately 50% SoC. this optimal level helps maintain the stability of the positive terminal structure and prevents permanent capacity loss due to electron depletion.
For more information on battery maintenance and charging practices, visit TechHelix Resources.
Refer to the Lithium Battery Storage Guide for detailed advice on long-term lithium storage.
The second factor affecting storage is the self-discharge rate. SLA batteries have a high self-discharge rate, so keeping them on a float or trickle charge is best. This keeps them as close to 100% state of charge (SOC) as possible, preventing sulfation reactions and permanent capacity loss. In contrast, lithium-ion batteries have a much lower discharge rate and do not need to be maintained at 100% SOC. if there are no parasitic loads such as Bluetooth modules, only minimal maintenance charging is required.
How do I prevent lithium-ion battery corrosion?
At Techhem, we have designed various features for the battery terminals to help you prevent corrosion! However, even with careful maintenance, batteries can corrode over time. You can minimize corrosion by following these steps:
An easy way to minimize the effects of corrosion is to store your batteries in a cool, dry environment. In addition to reducing corrosion, storing batteries in these conditions will extend their shelf life and lifespan.
The best way to prevent corrosion is to seal the terminals with a spray-on protector sold at most auto parts stores.
Inspect the terminals of your lithium battery regularly. Clean the terminals with a soft, dry cloth before use if they look dirty. This will prevent serious buildup that will be difficult to remove later.