How to Take Care of Your Lithium Iron Battery

Lithium iron batteries are becoming the popular choice as the standard battery in many applications. Knowing their characteristics helps maximize lifespan, safety, and performance.

What is a Lithium Iron Battery?

Lithium iron (LiFePO4 or LFP) is widely used today for its light weight and high energy density. Most lithium iron batteries consist of multiple LiFePO4 cells with a circuit board that protects the cells.

The cells are made up of a cathode, anode, separator, electrolyte, and two current collectors (positive and negative). The anode and cathode store lithium, while the electrolyte moves lithium ions through the separator. This ion flow charges the current collector, creating voltage that drives electrical current from the positive terminal to the application and back to the negative terminal.

How Do I Maintain a Lithium Battery?

Rechargeable lithium iron batteries have a finite life and, over time, will lose their ability to hold a charge. Once your battery has lost its capacity, it is permanent. Therefore, it is very important to properly care for and maintain your lithium battery.

An estimated life expectancy of a lithium iron battery is 5-15 years, depending on usage. LiFePO4 will provide up to 2000 complete charging cycles or as many as 6000 partial cycles! A complete charging cycle uses the battery from fully charged to fully discharged and then fully recharged. Leaving your batteries unused for long periods can hinder the life of the battery and ultimately lead to a failed battery if left too long.

We recommend cycling unused lithium batteries at least once every 6–12 months: charge to 100% SoC, discharge to 100% DoD, then charge to 50% SoC to maintain capacity. Check stored batteries for adequate OCV, and recharge any below the minimum recommended voltage listed in the table.

Voltage Range (V)	Lithium Iron Phosphate Product Type
3.3-3.4	Individual Cell
13.2-13.6	12-volt battery pack
26.4-27.2	24-volt battery pack
39.6-40.8	36-volt battery pack
52.8-54.4	48-volt battery pack

When checking cells or batteries semi-annually for voltage, please inspect for terminal corrosion and case integrity. Do not use any battery or cell that appears damaged.

LiFePO4 batteries self-discharge slowly in storage, with higher rates if features like Bluetooth are active. Periodically checking the charge helps maintain battery health and performance.

A good measure of health that’s easy to do at home is to monitor the run-time of your application. When you purchase your new lithium battery, note the run time the new battery provides your application. This brand-new run time will be a baseline to compare to as your battery ages to gauge your battery’s health. The run time will vary depending on the application and configuration that you are running.

How Do I Charge a Lithium Iron Battery?

A lithium-specific charger ensures complete cycles. Our LiFePO4 chargers use intelligent 3-step charging to revive deep discharges and optimize battery performance and lifespan.

But can a lead acid charger charge a lithium battery?

There are many similarities in the charging profiles of SLA and lithium. Exercise caution using SLA chargers on lithium batteries, as they can undercharge or damage them. Learn more in our blog, “Can I Charge a Lithium Battery With a Normal Charger?”

A 12V SLA battery’s full charge OCV is ~13.1V, and lithium’s is ~13.6V. Damage occurs only if charging voltage far exceeds these values.

Keep SLA bulk charging below 14.7V, lithium below 15V, and float charge SLA at ~13.8V. A 13.8–14.7V range safely charges both, so choose a charger within these limits.

What Charging Rate Will Extend the Life of a Lithium Battery?

Chargers are sized as a fraction of battery capacity: lithium can charge up to 1C (full capacity), while lead acid should stay below C/3. For a 10Ah battery, that’s 10A for lithium and ~3A for lead acid.

To balance fast charging and longevity, LiFePO4 batteries should charge between C/4 and C/2 (e.g., 2.5–5A for a 10Ah battery). Slower chargers maximize lifespan, while faster chargers reduce it.

Charge cutoff is 2.5–5% of capacity (0.25–0.5A in this example) and is usually handled by the charger. Universal chargers with chemistry selection help optimize battery life. This function chooses the optimal voltage charging range and determines when the battery is fully charged. For example, if it charges a lithium battery, the charger should shut off automatically. It should switch to a float charge if it is set to charge an SLA battery.

Long Term Storage

If you need to keep your batteries in storage for an extended period, there are a few things to consider as the storage requirements differ for SLA and lithium batteries.

First is that the battery’s chemistry determines the optimal storage SoC. For an SLA battery, you want to store it as close as possible to 100% SoC to avoid sulfating, which causes a buildup of sulfate crystals on the lead plates. The buildup of sulfate crystals will diminish the capacity of the battery.

For a lithium battery, the structure of the positive terminal becomes unstable when depleted of electrons for long periods. The instability of the positive terminal can lead to permanent capacity loss. For this reason, a lithium battery should be stored as near as possible to 50% SoC which equally distributes the electrons on the positive and negative terminals. For detailed recommendations on long-term Lithium storage, check out this guide regarding the storage of Lithium batteries.

The second influence on storage is the self-discharge rate. The high self-discharge rate of an SLA battery means that it is best to keep it on a float or trickle charge to maintain it as close as possible to 100% SOC to avoid sulfation and permanent capacity loss. For a lithium battery, which has a much lower discharge rate and doesn’t need to be at 100% SOC, you may be able to get away with minimal maintenance charging if there are no parasitic draws on the battery, such as a Bluetooth module.

How To Keep a Lithium-Ion Battery from Corroding?

Power-Sonic designed many features into the terminals of our batteries to help fight corrosion for you! However, even with care and maintenance, batteries can corrode over time. You can minimize the rate of corroding with any of the steps below.

• An easy way to reduce the effects of corrosion is to store your battery in a cool and dry environment. In addition to reducing corrosion, storing your battery under these conditions will increase the battery’s shelf life and life span.
• The best method to prevent corrosion is to seal your terminals using a spray-on protectant available at most auto parts stores.
• Continually inspecting your lithium battery terminals – if they appear dirty – and cleaning them with a soft dry cloth before use will prevent a large build-up that may later become difficult to remove.