Pros and Cons of lithium batteries and NiMH batteries in shelf life

In the battery industry, the term "Shelf Life" generally encompasses two distinct meanings:

1. Charge Retention (Self-Discharge Rate): If fully charged and put in a drawer, how long until the battery goes dead?

2. Calendar Life (Total Lifespan): Even if never used, how many years will the battery's chemistry last before degrading?

Below is a comparison of the pros and cons of Lithium batteries (specifically Li-ion/Li-Po) and Nickel-Metal Hydride batteries (NiMH) regarding these two dimensions:

1. Lithium Batteries (Li-ion / Li-Po)

General Characteristics: High energy density, ready to use, but chemically active with "natural aging" characteristics.

• Pros:

  • Extremely Low Self-Discharge (Holds charge well): The monthly self-discharge rate is typically only 1% - 5%. This means if you store it fully charged for six months or even a year, it will still have power when you take it out. This is great for occasional use (e.g., camera backup batteries).

  • No Memory Effect: Can be charged or stored at any time; no need to "drain completely before charging" like older battery technologies.

  • The King of Disposables (Primary Lithium): If referring to non-rechargeable Lithium Iron batteries (like Energizer Ultimate Lithium), their shelf life can reach 10-20 years. They are the best consumer batteries for long-term storage, perfect for emergency kits or smoke detectors.

• Cons:

  • Irreversible Calendar Aging (Fears "Old Age"): From the moment it leaves the factory, the internal chemistry begins to degrade, regardless of usage. Typically, the calendar life is about 3-5 years, after which capacity drops significantly.

  • Risk of "Deep Discharge Death": If stored at a low charge level for a long time (e.g., stored at 0% for 6 months), the voltage may drop below the protection circuit's cut-off threshold. This causes permanent damage, rendering the battery unable to accept a charge again.

  • Sensitive to Storage Environment: Storing at full charge in high temperatures accelerates aging (e.g., leaving a fully charged battery in a hot car in summer will drastically reduce its lifespan).

2. Nickel-Metal Hydride Batteries (NiMH)

General Characteristics: Safe and stable, the best alternative to alkaline dry cells, but traditional models "leak" charge quickly.

• Pros:

  • The Breakthrough of Low Self-Discharge (LSD): Note: This is the key differentiator.

    • Standard NiMH: Huge disadvantage. A full charge might drain itself in a month.

    • LSD NiMH (e.g., Panasonic Eneloop): Excellent performance. They can retain 70% capacity even after 5 to 10 years of storage after a full charge. In terms of long-term charge retention, high-quality LSD NiMH batteries are arguably better than standard Lithium-ion batteries.

  • Resilient to Over-Discharge: Even if a NiMH battery is accidentally drained to 0V, it can usually be "revived" and recharged. They are not as prone to immediate failure as Lithium batteries are.

  • Long Calendar Life: With proper maintenance, high-quality NiMH batteries can last 5-10 years.

• Cons:

  • High Self-Discharge in Standard Models (Major Drawback): If you buy non-LSD (standard) NiMH batteries, the monthly self-discharge rate can be as high as 20%-30%. You might charge them, put them in a drawer, and find them dead when you need them next month.

  • Memory Effect (Slight): Although much better than the old Nickel-Cadmium (NiCd) batteries, they can still lose some capacity if not fully cycled occasionally (though this can be fixed via a "refresh" cycle).

Summary & Comparison