Worried about your product's reliability? Using old batteries seems like a cost-saver, but it can lead to device failure, upsetting your customers and damaging your brand's reputation.
It is strongly advised not to use a lithium battery1 after its recommended use-by date, especially in commercial products. While it might still hold a charge, its performance is degraded, and the risk of safety hazards like swelling or leakage increases significantly, posing huge legal and financial risks.
This seems like a simple question, but the answer is complex. I've seen clients, even sharp ones like Michael from the US, consider this to cut costs. But the risks go far beyond just a battery that won't hold a charge. Let's break down what really happens when you push a battery past its prime. It's a conversation that could save your business a lot of trouble down the line.
What Happens If You Use Expired Batteries?
Your device suddenly fails, leaving a customer frustrated. The cause? An expired battery you thought was fine. This single component can undermine your entire product's quality and reliability.
Using expired batteries leads to poor performance and serious safety issues. You'll see reduced capacity, meaning shorter runtimes. The internal resistance increases, causing voltage drops under load. Worst of all, the risk of swelling, leaking, or even fire becomes a real and dangerous possibility for your product.
When a lithium battery ages, its internal chemistry changes, and not for the better. Two main things happen: performance drops, and safety becomes a gamble.
Performance Takes a Nosedive
The first thing you'll notice is a loss of capacity. A battery rated for 1000mAh might only deliver 700mAh after a few years on the shelf. For your product, this means shorter runtime and unhappy customers. I remember a new client developing a portable medical monitor. They tried using a batch of batteries that sat in a warehouse for over two years past the recommended date. Initially, the devices passed testing. But within three months, they saw a 30% failure rate in the field. The batteries couldn't deliver the stable power the device needed, causing it to shut down unexpectedly. The cost of the recall and replacement was massive, far more than the money they saved on the batteries.
Safety Becomes a Gamble
More importantly, the internal materials of the battery break down. The electrolyte can degrade, and the separator that keeps the positive and negative electrodes apart can become brittle. This increases the chance of an internal short circuit, which leads to overheating. This heat can cause the battery to swell up as gases are released inside. In the worst cases, it can leak corrosive chemicals or even catch fire. For a wearable or medical device that is in direct contact with a person, this is a risk you can never take.
| Feature | New Battery | Expired Battery (3+ years) | Impact on Your Product |
|---|---|---|---|
| Capacity | 100% of rated | 60-80% of rated | Shorter runtime, user complaints |
| Internal Resistance | Low | High | Device may shut down under load |
| Self-Discharge | Low (~1-2%/month) | High (~5-10%/month) | Battery drains quickly even when not in use |
| Safety Risk | Very Low | Moderate to High | Increased risk of swelling, leaking, or fire |
How to Check if a Lithium Battery Is Still Good?
You have a box of older batteries and are unsure if they're usable. Throwing them away feels wasteful, but using them is a risk. How do you make a smart decision?
To check a lithium battery, first, visually inspect it for any swelling, corrosion, or leaks. Next, use a multimeter to measure its voltage; a significantly low voltage often means it's permanently damaged. For a thorough analysis, a professional battery analyzer is needed to test its true capacity.
While I strongly advise against using old batteries in a final product, you might need to test some you have in stock. Here are the steps professionals take. But remember, these checks are for identifying clearly bad batteries, not for certifying old ones as good for production.
Step 1: Visual Inspection
Look at the battery closely. Do you see any of these warning signs?
- Swelling or Bulging: The battery casing should be perfectly flat. Any puffiness means gas has built up inside, and the battery is dangerous. Do not use it.
- Corrosion or Leaks: Look for any white or crystalline residue, especially around the terminals. This indicates the battery has leaked.
- Physical Damage: Check for dents, punctures, or damage to the outer wrapper. A compromised casing can lead to a short circuit.
Step 2: Voltage Check
You can use a simple digital multimeter to check the battery's open-circuit voltage. For a standard 3.7V lithium-ion cell, a healthy, fully charged battery should read around 4.2V. A battery at a nominal storage charge should be around 3.7-3.8V. If the reading is below 3.0V, and especially if it's below 2.5V, the battery has likely been over-discharged. Trying to charge it again can be hazardous.
Step 3: Professional Capacity Test
The only way to know the true health of a battery is to test its actual capacity. This requires a specialized battery analyzer. This machine performs a full charge-discharge cycle and measures exactly how much energy (in mAh) the battery can store and deliver. At Litop, our quality control team uses this equipment as part of our IQC (Incoming Quality Control) process. It tells us if a cell meets its stated specifications. This is not a quick check, but it is the most accurate one.
What Does the Date on a Lithium Battery Mean?
You see a date on a battery and assume it's an expiration date like on a milk carton. This misunderstanding can lead to costly mistakes in inventory management and production planning.
The date on a lithium battery is almost always the manufacturing date, not a strict expiration date. It serves as a starting point. Manufacturers use this date to calculate the battery's expected shelf life, which is typically 2-3 years under ideal storage conditions, before significant degradation begins.
Think of the date on a battery as its "birth date." It tells you when the battery's life journey began. From that day forward, the clock is ticking, and a process called calendar aging starts, whether the battery is being used or not.
The "shelf life" is the period during which the battery should retain most of its original capacity and performance, provided it is stored correctly. For most lithium-ion and lithium-polymer batteries, this is around 2 to 3 years. After this period, the rate of degradation increases more quickly.
Storage conditions are extremely important. A battery is like a living thing; its environment affects its health. The ideal way to store a lithium battery to maximize its shelf life is at a cool temperature and a partial state of charge.
| Storage Temperature | State of Charge | Capacity Loss (After 1 Year) |
|---|---|---|
| 0°C (32°F) | 40% | ~2% |
| 25°C (77°F) | 40% | ~4% |
| 25°C (77°F) | 100% | ~20% |
| 40°C (104°F) | 40% | ~15% |
| 60°C (140°F) | 40% | ~25% |
As you can see, storing a fully charged battery, especially in a warm place, is the fastest way to ruin it. That's why at Litop, we are so strict about our climate-controlled warehouses and our shipping procedures. We ensure the batteries you receive from us haven't lost a big chunk of their life before they even get to you.
Is It Safe to Use Old Lithium Batteries?
Saving money by using old batteries seems tempting. But are you unknowingly putting your product, your customers, and your company's reputation at serious risk of a safety incident?
No, it is generally not safe to use old lithium batteries in a commercial product. The internal components degrade over time, increasing the risk of internal short circuits. This can lead to overheating, swelling, leakage, and even fire, creating a significant liability for your brand.
This is the most important question, and my answer is always a firm no. This is where the conversation moves from performance to risk management.
I often discuss this with my client, Michael. He runs a company in the United States that makes high-end medical devices2, and he understands that product liability is a huge concern. I always tell him, "Michael, if a device fails and causes harm, lawyers and investigators will look at every component. If they find an expired battery, the case is almost closed." Your company knowingly used a part that was past its recommended service life. The few dollars you saved on that battery could lead to millions in lawsuits, a full product recall, and a complete loss of trust in your brand.
In strictly regulated markets like the US, Europe, and Japan, this is a non-starter. You could even lose your certifications to sell in those regions. It's a legal and financial time bomb.
The small amount of money saved on sourcing expired batteries is nothing compared to the potential costs. Think about it:
- Repair and Replacement Costs: Handling warranty claims for failed devices.
- Brand Damage: Negative reviews and loss of customer loyalty.
- Legal Fees and Fines: The cost of defending your company in a lawsuit.
- Loss of Major Contracts: Big clients will not work with a supplier who cuts corners on safety.
Using an old battery is like building a house on a weak foundation. It might stand for a while, but eventually, it will fail. And when it does, the damage will be catastrophic.
Conclusion
Using expired lithium batteries is a bad business decision. The performance loss, safety hazards, and legal liabilities far outweigh the minimal cost savings. To protect your product, your customers, and your brand, always source fresh, certified batteries from a trusted supplier like Litop.
