Battery Storage Guide: How to Store LFP and NMC Batteries Long-Term?

Storing batteries long-term seems simple, but a small mistake can ruin your inventory. This can lead to significant financial loss and even create serious safety hazards on your shelves.

To store LFP (LiFePO4)¹ and NMC (Nickel Manganese Cobalt)² batteries long-term, you must keep them in a cool, dry place. Store LFP batteries at a 50-70% State of Charge (SoC) and NMC batteries at a 40-50% SoC to minimize degradation and ensure safety.

I’ve been in the battery business for over 8 years, and I’ve seen how storage practices can make or break a project. It’s not just about putting batteries on a shelf anymore. Especially now, with new regulations in Europe and the US, storing batteries has become a matter of managing data and risk. Getting it wrong can lead to your shipment being seized or heavy fines. But getting it right protects your investment and ensures your products perform exactly as intended. Let’s break down how to do it correctly.

How to prolong NMC battery life?

NMC batteries are powerful, but they are also sensitive. Storing them the wrong way can slash their lifespan and performance, which is a waste of your investment. But a few simple adjustments can help them last much longer.

To prolong NMC battery life, store them at a 40-50% State of Charge (SoC) in a cool environment, ideally between 15°C to 25°C. You must avoid extreme temperatures. Also avoid keeping them fully charged or fully empty during long-term storage, as this speeds up capacity loss.

NMC batteries are the workhorses for many high-performance devices, but their chemistry requires careful handling during storage. The two biggest enemies of an NMC battery’s health are high voltage and high temperature. When you combine them, you create the perfect storm for battery degradation. I once had a client who stored a large batch of fully charged NMC batteries in a warehouse that got hot during the summer. After six months, they had lost nearly 20% of their capacity before ever being used. This was a costly lesson in battery chemistry.

The Critical Role of State of Charge (SoC)

Storing an NMC battery at 100% charge is like holding a rubber band stretched to its limit. The high voltage puts constant stress on the battery's internal structure, especially the cathode. This accelerates the growth of the Solid Electrolyte Interphase (SEI) layer, an internal film that consumes lithium ions and increases internal resistance. Over time, this leads to permanent capacity loss. By storing it at around 40% SoC, you lower the voltage and relieve this stress, slowing down the aging process significantly.

Temperature: The Silent Killer

Heat acts as a catalyst for all the unwanted chemical reactions inside a battery. The higher the temperature, the faster your battery degrades. Storing batteries in a non-climate-controlled warehouse or near a heat source is one of the fastest ways to destroy them. The table below shows just how much temperature and SoC can affect capacity.

As you can see, a simple change in storage habits can be the difference between a healthy battery and a useless one.

How to store LFP batteries?

LFP batteries are famous for their safety and long life. But you can't just assume they are indestructible. If you don't follow proper storage guidelines, you can still face unexpected capacity loss over time.

For LFP (LiFePO4) batteries, you should store them at a 50-70% State of Charge (SoC). Keep them in a dry place with stable temperatures, ideally around 25°C. Their strong chemistry makes them less sensitive than NMC batteries and gives them a wider storage window.

LFP batteries are becoming a favorite for many of my clients, especially those who need to hold inventory for longer periods. Their inherent stability comes from the olivine crystal structure, which features strong covalent bonds. This structure is incredibly resilient and less prone to breaking down under stress, which is why LFP batteries are so much safer and less likely to experience thermal runaway. This chemical stability is a huge advantage, but it also translates into a hidden financial benefit when it comes to storage. It’s what I call the "hidden dividend" of LFP.

LFP's Inherent Stability

The reason you can store LFP batteries at a higher SoC (50-70%) is because their voltage curve is very flat in this middle range. This means the internal voltage doesn't change much, so there's very little stress on the battery's components. Unlike NMC, there is no high-voltage stress pushing the battery to degrade. This, combined with its resistance to high temperatures, makes LFP far more forgiving. Its self-discharge rate is also incredibly low, often less than 2% per month, so you don't have to check and recharge it as often as other chemistries.

The Total Cost of Ownership Advantage

When choosing a battery, many people focus only on the initial purchase price. But for long-term storage, you have to look at the total cost of ownership. LFP batteries might sometimes have a similar or slightly higher upfront cost, but they save you money in the long run. Because they are safer, insurance premiums for storing them are often lower. You also don't need as strict of a climate-controlled environment, which saves on energy costs. Most importantly, their lower degradation rate means less inventory loss over time.

A client of mine, Michael, who develops medical devices, switched to LFP for this exact reason. His products sometimes sit in inventory for over a year. The lower insurance costs and near-zero capacity loss made LFP the clear winner, saving his company thousands.

What is the 40 80 rule for batteries?

You probably hear rules of thumb for batteries, like the "40-80 rule³." But what does it really mean? If you misunderstand this simple rule, you could be shortening your battery's life every day without even knowing it.

The 40-80 rule is a guideline for daily battery use, not for long-term storage. It suggests you keep your lithium-ion battery's charge between 40% and 80%. This practice minimizes stress on the battery, reduces degradation, and can significantly extend its overall cycle life.

This rule is all about minimizing stress during a battery's active life. Think of a battery's charge level like a person's blood pressure. You don't want it to be too high or too low for long periods. The same is true for a battery. The states of being fully charged (100%) and fully discharged (0%) are the most stressful for its chemistry. While our devices are designed to handle this, constantly pushing the battery to these limits will wear it out much faster. The 40-80 rule is simply a strategy to keep the battery in its happiest, most stable state as often as possible.

Why Avoid the Extremes?

When you charge a battery to 100%, the voltage is at its peak. This high voltage accelerates wear on the cathode, one of the key components. On the other end, when you discharge a battery completely to 0%, the voltage drops very low. This risks over-discharging, which can cause permanent damage like the dissolution of copper components inside the cell, leading to a dead battery. Staying within the 40% to 80% range keeps the voltage in a stable, middle ground, putting the least amount of strain on the battery.

Cycle Life vs. Depth of Discharge

The 40-80 rule is directly related to the concept of Depth of Discharge (DoD)⁴. A 100% DoD means you use the battery from full to empty. A 40% DoD means you only use 40% of its capacity before recharging (e.g., from 80% down to 40%). As you can see in the table below, shallower discharge cycles dramatically increase the total number of cycles you can get from a battery.

For many of our B2B clients making medical or IoT devices, we help them implement this logic directly into their product's Battery Management System (BMS). The device can then automatically manage its charging to optimize for a long service life.

How to properly store batteries long term?

Storing batteries used to be an easy task, but new regulations are turning it into a minefield. A simple mistake in compliance can get your entire shipment rejected by a warehouse, costing you a lot of time and money.

To properly store batteries long-term, maintain the correct State of Charge (40-50% for NMC, 50-70% for LFP) in a cool, dry, climate-controlled environment. More importantly, you must now comply with all local fire, safety, and insurance regulations, which are becoming much stricter.

The game has changed. I recently spoke with a procurement officer from a large US company, and he told me that compliance is no longer a "choice" but a "survival issue." Warehouses in the US and Europe are now enforcing strict rules based on the latest fire codes and insurance requirements. They won't even accept your batteries without the right paperwork and proof of compliance. This means your storage strategy has to be about more than just temperature and charge level; it has to be about risk management and documentation.

Beyond Temperature and SoC: The New Era of Compliance

Storing batteries today is about managing data and risk. Before your batteries even arrive at a warehouse, you need a complete documentation package. This includes the Material Safety Data Sheet (MSDS)⁵, UN38.3 test reports⁶, and any other certifications required for your market (like CE, UL, or RoHS). The storage facility itself must meet specific fire codes, which often include requirements for shelf spacing, specialized fire suppression systems (like Class D extinguishers), and proper ventilation to prevent any gas buildup. Failure to meet these standards can result in your inventory being rejected or even seized by authorities.

A Practical Checklist for Long-Term Storage

To make this easier, I've put together a checklist that we use with our clients to ensure their storage plan is solid from start to finish. Following these steps will help you protect your investment and avoid any costly surprises.

We at Litop help our partners navigate these requirements every day. It's now a standard part of our service to provide a full documentation package and advise on storage compliance.

Conclusion

To sum it up, store NMC batteries at 40-50% SoC and LFP at 50-70% in a cool place. Remember, LFP often has a lower total storage cost. The 40-80 rule is for daily use. Most importantly, always follow storage regulations to protect your business and your investment.