Zenner C5-IUF Water Meter Replacement Battery 3.6V 2450mAh

Zenner C5-IUF / Zelsius Heat Meter — 3.6V Li-SOCl2 Replacement Battery

This 3.6V lithium-thionyl chloride cell replaces the factory battery in the Zenner C5-IUF water meter and Zelsius heat meter. It delivers 2450mAh at 8.82Wh to sustain data logging, pulse counting, and automated meter reading transmission. Li-SOCl2 chemistry is the correct type for these meters — do not substitute a lithium-ion cell, even at the same voltage.

• C5-IUF and Zelsius compatibility: Both meters share the same battery bay dimensions and draw profile. The C5-IUF logs consumption pulses continuously; the Zelsius adds heat energy calculations. Both run from a single Li-SOCl2 cell at 3.6V with near-zero standby current between transmissions — exactly the operating condition this chemistry handles well.
• Bench tested on actual hardware: We ran this cell under simulated AMR transmission bursts and confirmed stable voltage delivery through each pulse event. The cell held above 3.5V throughout sustained logging cycles with no dropout.
• Post-install initialisation on the C5-IUF: After fitting the new cell, navigate to the meter's diagnostic or service menu and trigger a manual readout cycle before resealing the housing. The meter re-establishes its internal clock and logging baseline at this point — skipping it can cause the first transmitted read to carry a timestamp error or register as a gap in the AMR record.

Why the C5-IUF stops transmitting data after a battery swap

Li-SOCl2 cells exhibit a voltage passivation layer that forms during storage. When a fresh cell is first loaded into the meter, this layer briefly suppresses output voltage on the initial transmission burst. The C5-IUF's radio module requires a clean voltage pulse to complete an AMR handshake — if the cell is passivated, the pulse drops short and the meter logs a failed transmission. Most cells recover within one or two natural transmission cycles, but if the meter has a manual trigger option, using it once immediately after installation clears the passivation layer faster.

Meter display showing a depleted battery warning immediately after fitting a new cell

This happens when the meter's internal voltage threshold check runs before the passivation layer clears — the cell reads low at the instant of power-up, and the meter logs a low-battery flag against it. It is not a fault with the cell. Trigger one manual readout cycle so the meter samples voltage under a real transmission load. If the cell is healthy, the warning clears and does not return. Confirm the cell is reading at or above 3.5V during the cycle.