Primary lithium batteries are high-energy new-type batteries featuring high specific energy, high voltage, wide operating temperature range, long storage life, environmental friendliness and zero pollution. Nevertheless, any battery selected must match the operating conditions of the electrical equipment. Below we elaborate on key technical considerations for primary lithium battery selection to serve as a reference for customers.

1. Open-Circuit Voltage

Open-circuit voltage refers to the voltage of a battery with no load, whose value is determined by its electrochemical system. Among the most widely used primary lithium batteries:

• Lithium-manganese dioxide batteries have a nominal voltage of 3.0 V;
• Lithium-thionyl chloride batteries have a nominal voltage of 3.6 V;
• Lithium-iron disulfide batteries have a nominal voltage of 1.5 V.

2. Polarization Curve

A battery delivers its open-circuit voltage under no-load conditions. Once current is drawn, the output voltage deviates from the open-circuit voltage — this deviation is defined as polarization. Polarization consists of three components: ① Ohmic polarization: Caused by the battery’s internal resistance, proportional to operating current; ② Activation polarization: Determined by the slow electron transfer step in electrochemical reactions; ③ Concentration polarization: Governed by the ion concentration gradient near electrode surfaces.

Polarization rises with operating current; the higher the discharge current, the more severe the polarization.

Due to polarization during current discharge, a battery’s operating voltage varies under different discharge currents and declines as current increases. For example, batteries used in smart flow meters run at low current under normal conditions, maintaining a relatively high and stable operating voltage. When a large pulse current is required (e.g., for electric valve actuation), the sharp current surge triggers a substantial voltage drop, an inherent characteristic of batteries. In short, the operating voltage under high-current pulses is noticeably lower than the normal working voltage — a critical point users must bear in mind.

3. Battery Capacity

Battery capacity is measured in milliampere-hours (mAh), calculated as the product of operating current and discharge duration. Discharge duration denotes the time taken for a battery to discharge down to its cut-off voltage. Capacity is directly proportional to the quantity of active materials inside the battery: larger battery housings contain more active materials and thus deliver higher capacity.

The rated capacity specified by manufacturers is measured under standard ambient temperature (20 ℃ ± 5 ℃), calculated by multiplying the standard continuous discharge current by the discharge time until the defined cut-off voltage is reached. Extremely low temperatures or discharge currents far exceeding the standard value will prevent the battery from releasing its full rated capacity.

Furthermore, performance differs drastically between new batteries and those after prolonged use; battery performance degrades as active materials are consumed. Users should therefore reserve an appropriate safety margin when choosing battery capacity. Please consult the manufacturer for detailed specifications.

4. Standard Discharge Current

The standard discharge current is the continuous current at which a battery can deliver its full nominal capacity when discharged continuously to the specified cut-off voltage (2.0 V) under defined temperature conditions. Exact parameters shall comply with manufacturer specifications.

5. Maximum Continuous Operating Current

Defined as the maximum continuous discharge current at 20 ± 2 ℃ that enables the battery to release 50% of its rated capacity when discharged continuously down to the 2.0 V cut-off voltage.

6. Maximum Pulse Operating Current

Refers to the maximum pulse output current for a battery that has already discharged 50% of its rated capacity, tested at 20 ± 2 ℃ with a pulse duration of 10 seconds and a minimum operating voltage of 2.0 V.

7. Battery Power

Power equals the product of battery operating voltage and discharge current, serving as a metric for a battery’s output capability. Within a fixed electrochemical system, battery power is primarily determined by internal structure. Batteries are generally categorized into power-type and energy-type designs:

• Power-type batteries support high-current discharge with relatively low capacity, suited for devices requiring high output power;
• Energy-type batteries operate at low discharge currents with relatively high capacity, ideal for equipment with long-duration low-current operation.

No direct correlation exists between battery capacity and power rating.

8. Operating Temperature Range

Primary lithium batteries typically operate within -20 ℃ to +60 ℃ (special high-temperature variants can withstand up to 150 ℃). Exceeding the upper temperature limit may lead to battery failure or even explosion; temperatures below the rated lower limit will render the battery incapable of discharging. Even within the specified low-temperature range, battery output performance deteriorates as temperature drops. Please consult the manufacturer for stable operation under extreme high or low temperature environments.

9. Voltage Delay Phenomenon

Voltage delay describes the phenomenon where a battery’s operating voltage drops sharply immediately after connecting to a load, then recovers to its normal operating voltage after several seconds. This effect stems from the passivation film formed on the negative electrode surface and occurs mainly in lithium-thionyl chloride batteries; lithium-manganese dioxide batteries generally exhibit no such delay.

10. Storage Life

Primary lithium batteries boast superior storage performance compared to all other primary battery types. Under normal room temperature and humidity, their annual self-discharge rate is only 1–2%, delivering a storage life of over 6 years, with top variants reaching 10 to 15 years. This makes them perfect for maintenance-free equipment with long-term low-current operation. However, long-term storage under high temperature or high humidity will shorten service life.

11. Battery Safety

Lithium primary batteries are high-energy devices, and lithium is an extremely reactive metal, creating inherent potential safety hazards. Improper handling during charging, transportation, storage, assembly or application may trigger safety incidents. Strictly prohibited operations include charging, squeezing, incinerating, short-circuiting and disassembling the batteries, all of which may cause electrolyte leakage, combustion or explosion.

Power-type batteries feature strong output performance and therefore pose more prominent safety risks. Assembled battery packs impose stricter safety requirements, so users are advised not to assemble battery packs on their own — this work must be performed by professional battery manufacturers. Equipment designers shall integrate battery safety requirements into product design to guarantee product quality. We welcome in-depth discussions with you regarding all battery safety-related matters.