Varta 3/V80H Ni-MH

Varta 3/V80H Ni-MH Rechargeable Pack (3.6V) — Compact Backup Power

The Varta 3/V80H is a three-cell Ni-MH pack built from V80H cells to provide a nominal 3.6V in a very small footprint. It is purpose-built for low-current, always-on standby roles such as memory and RTC retention, alarm and sensor keep-alive, and small industrial electronics.

Key specs and fit notes

Chemistry	Nickel-Metal Hydride (Ni‑MH)
Configuration	3 × V80H in series (3/V80H)
Nominal voltage	3.6 V
Nominal capacity	≈ 80 mAh (pack capacity equals a single V80H cell)
Intended use	Backup/standby power (low, continuous current)
Mounting/termination	Varies by variant (e.g., solder tabs, pins, leads). Verify before ordering.

Note: For exact dimensions, pinout, and allowable charge rates, consult the specific variant datasheet.

When to choose this pack

• Your device expects a rechargeable 3.6V backup source with a trickle-charge circuit.
• Space is limited and loads are low (microamps to a few milliamps).
• You need a serviceable, cadmium-free alternative to older 3.6V Ni-Cd packs.

When to consider alternatives

• Long shelf/storage with no charging available: Use a primary lithium coin cell (e.g., CR series). Do not charge primary cells.
• Longer runtime at the same load: Consider higher-capacity Ni‑MH packs such as 3/V110H or 3/V150H (if space allows).
• Very high pulse currents or instant recharge: Evaluate a supercapacitor (ensure your circuit tolerates voltage droop), or a larger rechargeable pack.

Runtime examples (approximate)

Estimate: runtime (hours) ≈ 80 mAh ÷ load (mA). Actual runtime will be lower due to self‑discharge and temperature.

• 10 µA load → ≈ 8,000 h (~11 months)
• 50 µA load → ≈ 1,600 h (~2.2 months)
• 1 mA load → ≈ 80 h (~3.3 days)

Charging guidance (typical for Ni‑MH backup cells)

• Trickle charge: 0.02–0.05 C recommended for standby use (≈ 1.6–4 mA for an 80 mAh cell/pack).
• Fast charge: Only if the device supports proper termination (-ΔV/dt, temperature). Not typical for backup roles.
• Temperature: Charge generally between 0–45°C; discharge typically -20–60°C.
• Self‑discharge: Expect gradual capacity loss during storage; keep the pack topped up in-circuit.

Installation and care

• Use the correct variant (tabs/pins/leads). Avoid soldering directly to cell cans.
• Observe polarity; mount securely to minimize vibration and lead stress.
• Do not mix old and new packs or different chemistries.
• Store cool and dry (ideally 10–25°C). Top up every few months if stored off-charge.

Environmental and safety notes

• Ni‑MH chemistry avoids the cadmium found in older Ni‑Cd cells.
• Do not short-circuit, crush, or incinerate. Dispose/recycle in accordance with local regulations.
• No built-in protection PCB; rely on the host device for proper charging/termination.

FAQ

Can I replace a 3.6V Ni‑Cd backup pack with the 3/V80H Ni‑MH?

Often yes for low-rate trickle‑charged systems, but confirm the device’s charge algorithm and current. Ni‑MH prefers lower trickle rates and different termination than Ni‑Cd.

Is continuous trickle charging safe?

Yes if the current stays within the manufacturer’s specified trickle range (e.g., 0.02–0.05 C) and ambient temperature is controlled.

What if my device originally used a lithium coin cell?

Do not substitute. Primary lithium cells are not rechargeable. Only use the chemistry and charging method the device was designed for.

How do I estimate backup time?

Divide 80 mAh by your standby current (in mA). Then reduce the result to account for self‑discharge, temperature, and device cut‑off voltage.

How do I know the pack is at end of life?

Noticeably shorter backup time, rising self‑discharge, or inability to reach/hold charge under a known-good charger are common indicators.