Leclanché cells lose low-temperature performance faster than zinc chloride cells. As temperature falls below 0°C, electrolyte conductivity and reaction kinetics decline, causing internal resistance to rise and usable discharge capacity to fall. In environmental testing, Leclanché cells retain roughly 65% of room-temperature capacity at 0°C and can become effectively inoperative below −20°C; zinc chloride cells retain about 80% at 0°C because their electrolyte remains fluid over a wider sub-zero range.
The key distinction is electrolyte behavior: both systems suffer higher resistance and lower capacity in the cold, but zinc chloride cells generally maintain discharge performance longer because their concentrated electrolyte resists slushing and freezing more effectively than the electrolyte in conventional Leclanché cells.
Why Sub-Zero Temperatures Increase Internal Resistance
Reduced ionic conductivity
Cold temperatures increase electrolyte viscosity and reduce ion mobility. This makes it harder for ions to move between the electrodes, increasing the cell’s internal resistance.
The result is a larger voltage drop under load, even when the cell still contains chemically available active material.
Slower electrochemical reactions
Lower temperature also slows electrode reaction kinetics. The cell therefore polarizes more readily during discharge, reducing the voltage plateau and preventing complete utilization of the active materials.
This is why measured capacity depends on both temperature and discharge rate. High-current loads expose the resistance increase more severely than low-current loads.
Resistance growth in Leclanché cells
For a representative D-size Leclanché cell, internal resistance can increase from approximately 0.5 Ω at 20°C to about 2 Ω at −20°C.
That fourfold increase substantially magnifies the load-induced voltage drop. A cell may still show an open-circuit voltage while failing to deliver useful power under practical discharge conditions.
How Discharge Capacity Changes
Leclanché performance
Leclanché cells typically show a pronounced capacity reduction as temperature approaches and passes below freezing.
At 0°C, available capacity may fall to approximately 65% of its room-temperature value. Below about −20°C, the cell can become essentially inoperative because the combination of high resistance, sluggish reactions, and electrolyte solidification prevents effective discharge.
Zinc chloride performance
Zinc chloride cells generally provide better sub-zero discharge performance. At 0°C, they can retain approximately 80% of room-temperature capacity, subject to the specified load and test method.
Their advantage is not immunity to cold. Resistance still increases and capacity still declines, but the degradation is less severe over the initial sub-zero range.
The role of electrolyte concentration
Zinc chloride formulations commonly use approximately 25–30 wt% zinc chloride. This electrolyte typically forms a slush near −20°C and freezes near −25°C.
Those limits explain the performance pattern: zinc chloride cells can outperform Leclanché cells around 0°C and moderately sub-zero conditions, but their advantage diminishes sharply as slushing and freezing begin.
What Environmental Testing Reveals
Capacity is a test-condition measurement
“Capacity” is not a fixed value independent of temperature. It depends on the cutoff voltage, discharge current, duty cycle, cell size, and thermal history.
A cell tested at a low continuous current may deliver more apparent capacity than the same cell tested under a high-current pulse load at the same temperature.
Internal resistance exposes practical failure earlier
Resistance measurements often reveal low-temperature degradation before a capacity test is complete. As resistance rises, the terminal voltage collapses more quickly during load application.
Testing should therefore track both total internal resistance and voltage response under load, rather than relying only on ampere-hours delivered.
Environmental chambers are essential
A controlled chamber allows the cell to equilibrate at a defined temperature before and during discharge. This separates genuine temperature effects from temporary thermal gradients or self-heating.
A suitable test system should record temperature, current, terminal voltage, cutoff events, and resistance or pulse-voltage behavior throughout the test.
Comparing the Two Systems
Leclanché: stronger temperature sensitivity
Leclanché cells are more vulnerable to cold-induced resistance growth and capacity loss. Their performance can deteriorate substantially by 0°C and may become practically unusable below −20°C.
They are therefore less suitable when reliable operation is required during sustained sub-zero exposure.
Zinc chloride: improved but bounded performance
Zinc chloride cells offer better low-temperature capability because their electrolyte remains usable at lower temperatures before slushing or freezing occurs.
However, “better” does not mean “cold-proof.” Once the electrolyte approaches its slush or freezing range, internal resistance rises sharply and discharge capacity falls rapidly.
Understanding the Trade-offs
Low-temperature capability versus formulation limits
Increasing electrolyte concentration can depress the freezing point and improve cold performance, but every formulation still has a practical thermal boundary.
The zinc chloride system’s approximate slush and freezing limits should be treated as operating constraints, not merely laboratory observations.
Capacity retention versus discharge rate
The reported 65% and 80% capacity values are representative environmental-test results, not universal specifications. Higher discharge rates generally produce greater apparent capacity loss because the increased resistance causes the cutoff voltage to be reached sooner.
Resistance data versus capacity data
A resistance measurement does not directly equal available capacity. It indicates how strongly the cell’s terminal voltage will respond to load, while capacity testing measures how long the cell can sustain a defined discharge condition.
Both measurements are needed to distinguish chemical depletion from cold-induced power limitation.
Avoiding misleading comparisons
Leclanché and zinc chloride cells should be compared using the same cell size, temperature stabilization time, discharge profile, cutoff voltage, and measurement method.
Otherwise, an apparent chemistry advantage may actually result from different test conditions.
Making the Right Choice for Your Goal
The appropriate system depends on whether the application prioritizes nominal cost and ordinary-temperature operation or sustained output in cold environments.
- If your primary focus is ordinary indoor operation: Leclanché cells can be suitable, but expect meaningful capacity loss as temperature approaches 0°C.
- If your primary focus is sub-zero discharge capability: Prefer zinc chloride cells, which generally retain more capacity and lower effective resistance near 0°C.
- If your primary focus is operation below −20°C: Treat both chemistries as thermally constrained and verify performance experimentally, because electrolyte slushing, freezing, and resistance growth may prevent useful discharge.
- If your primary focus is environmental qualification: Measure capacity together with internal resistance and load-induced voltage drop across a controlled temperature profile.
For cold-environment applications, zinc chloride is generally the stronger choice, but only temperature-controlled testing can establish the cell’s actual operating limit.
Summary Table:
| Parameter | Leclanché Cells | Zinc Chloride Cells |
|---|---|---|
| Capacity retention at 0°C | ~65% of room-temperature capacity | ~80% of room-temperature capacity |
| Internal resistance increase | ~0.5 Ω at 20°C to ~2 Ω at −20°C (4x increase) | Better resistance stability at moderate sub-zero temps |
| Usable low-temperature limit | Becomes inoperative below about −20°C | Operates until electrolyte slush ( |
| Electrolyte behavior | More prone to viscosity increase and freezing | Concentrated electrolyte resists slushing and freezing better |
| Suitability for sub-zero use | Less suitable for sustained cold operation | Generally preferred for better low-temperature performance |
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