Battery Capacity After Four Years of Storage

In 2021, I initiated an extended test to determine how ordinary battery capacity diminishes over several years of storage and whether manufacturers' claims about 12-year shelf life are credible.

I purchased 192 AAA-format batteries from eight brands. Each September, I test two batteries of each type and compare results with previously obtained data.

Test Subjects

The test includes six alkaline (LR03) battery models:

• Duracell Ultra (manufactured in Belgium)
• Energizer Max+ with 12-year shelf life (made in USA)
• Varta Longlife Power (made in Germany)
• GP Super
• Lexman Standard (Leroy Merlin store brand)
• FLARX (Fix Price store brand)

Two salt-based (R03) battery types also participate:

• Auchan store brand with bird logo
• Trofi

When purchasing, I selected the freshest available batteries — 5-10 months old from manufacturing date at initial testing.

Leakage Issues

Before the first test, one Energizer Max+ unexpectedly leaked. After three years, Varta Longlife Power batteries leaked massively: five of sixteen remaining units failed. By year four, six had leaked severely with three more showing warning signs.

Salt batteries have a three-year shelf life, already expired 18 months prior to this test. Some Trofi salt batteries began degrading after four years — not leaking yet, but showing discoloration under the packaging with voltage dropping below 0.7V.

Voltage Measurements

I test two specimens simultaneously to eliminate single-unit defects. Voltage was measured on identical samples using the same precision instrument throughout.

Voltage drop on alkaline batteries:

• 0.7-1.2% per year
• 1.2-2.7% over two years
• 1.9-2.9% over three years (except Varta at 3.6-7.5%)
• 2.3-3.5% over four years (Varta excluded due to leakage)

Salt battery voltage drop:

• 2-2.4% yearly
• 3.2-3.5% over two years
• 4.2-6.2% over three years
• 5.1-6.1% over four years

Capacity Testing

Batteries were tested using a "Yarostanmash ASK2.5.10.8" chemical source analyzer in early September 2025. Units were discharged at 100mA to 0.9V, recording energy output in milliwatt-hours, capacity in milliampere-hours, and internal resistance in ohms.

Key Findings

After four years, several conclusions emerge:

Quality extends beyond initial capacity. Some batteries lose significant capacity during storage and leak — notably Varta (authentic German manufacturing). This is the most important finding: a premium brand with real German production proved the least reliable for long-term storage.

Capacity loss varies substantially. Salt batteries lose over 10% in four years (acceptable given their three-year shelf life). Inexpensive FLARX alkaline units lost 11% over four years (justified by their stated three-year shelf life). Energizer performed best with under 2% loss over four years; GP lost 4.5%.

When purchasing, note manufacturing dates. Buy units no older than one year. Some manufacturers list only the shelf-life expiration date — subtract seven years from that date to determine the manufacturing date.

The test will continue. Next year I will test another pair of batteries from each brand and update the results.