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Deep within countless industrial motherboards, legacy computers, CNC machine tools, and precision instruments lies a small, unassuming cylindrical battery. Whether tightly wrapped in heat-shrink tubing or resting quietly beneath the casing of an RTC chip, it bears the model designation "VARTA 3/V200H." This tiny capsule of energy silently safeguards device configurations, time settings, and calibration data, allowing the machine to "remember" its identity even after power is lost. Today, we take a closer look at this classic Ni-MH rechargeable battery pack.

What exactly is it?

The VARTA 3/V200H is not a single cell, but a rechargeable nickel-metal hydride (Ni-MH) battery pack consisting of three cells connected in series. It comprises three VARTA V200H button-style Ni-MH cells—each with a nominal voltage of 1.2V—packaged together in a compact cylindrical form, resulting in a total nominal voltage of 3.6V and a typical capacity of 200mAh. It is also commonly referred to by designations such as "3.6V 200mAh Ni-MH battery pack."

This battery is specifically designed for memory backup applications requiring long-term trickle charging and low discharge currents. Commonly found in:

Replacement batteries inside RTC modules such as the Dallas DS12887 / DS12C887 (many enthusiasts cut open the module casing to replace the dead original battery with a 3/V200H).

SRAM backup power supplies for industrial CNC systems (e.g., Siemens, Fanuc).

CMOS memory batteries on vintage computer motherboards.

Calibration data retention circuits in oscilloscopes, spectrum analyzers, and medical instruments.

Specifications Overview

Item Parameter

Model VARTA 3/V200H

Type 3-cell series Ni-MH rechargeable battery pack

Nominal Voltage 3.6V

Standard Capacity 200mAh

Standard Charging 0.03–0.05C long-term float charge, or 20mA trickle charge

Cell Dimensions Single V200H cell: approx. φ25.2 × 6.3 mm

Pack Configuration Usually heat-shrink wrapped; includes solder tabs or lead wires

Operating Temperature -20°C to +60°C

Typical Lifespan 5–10 years (under float charge conditions)

Silent Warning Signs of Aging

When this battery reaches the end of its life, the device usually does not trigger an alarm; instead, it quietly "loses its memory":

Time Reset: After power-off, the system clock reverts to the factory default date (e.g., 1980 or 2000).

Loss of BIOS/CMOS Settings: A "CMOS Checksum Error" appears upon startup; hard drive parameters and boot sequences are lost.

Loss of Calibration Data: Precision instruments lose calibration coefficients after a power cycle, causing measurement drift.

Leakage and Corrosion: More dangerously, severely aged Ni-MH batteries may leak alkaline electrolyte, corroding solder pads and PCB traces, resulting in irreversible physical damage.

If you observe any of the above symptoms, the first step is to check the 3/V200H battery. Use a multimeter to measure the voltage; the normal float-charge voltage should be around 3.9V–4.2V (trickle charge state). If the open-circuit voltage drops below 3.0V—or even close to zero—the battery has reached the end of its service life.

**Practical Replacement Guide and Pitfalls to Avoid**

Replacing the VARTA 3/V200H is a common task for electronics enthusiasts and equipment maintenance engineers. The process is not complex but requires care.

**Brief Overview of Replacement Steps**

**Locating and Removal:** Locate the cylindrical battery on the motherboard or module; it is usually secured with cable ties, a bracket, or soldered directly to the pads. Take a photo to record the polarity (positive/negative orientation).

**Desoldering:** Use a solder sucker and an anti-static soldering station to quickly detach the old battery leads from the pads, avoiding prolonged heating that could damage the circuit board.

**New Battery Preparation:** Most commercially available 3/V200H units come with pre-soldered axial leads (single-ended or double-ended output). Measure the required lead spacing accurately and adjust the shape if necessary.

**Soldering:** Solder the new battery back in place, observing the original polarity. **Mind the polarity!** Reversing it can cause a short circuit through the diode, potentially blowing the current-limiting resistor or even damaging the chip.

**Power-on Test:** Once assembled, power up the motherboard and measure the battery terminal voltage. Confirm it fluctuates within the 3.9V–4.2V range, indicating the float-charge circuit is functioning correctly. Power down briefly and restart to ensure the timekeeping remains accurate.

**Points to Consider When Purchasing**

**Check the Brand:** Prioritize genuine VARTA batteries; brand-new stock is still available on the market. Some domestic alternatives offer stable performance, but ensure you select a Ni-MH battery pack explicitly rated for 3.6V and a capacity of ≥200mAh.

**Inspect Appearance:** Genuine products feature tight packaging, smooth heat-shrink wrapping, clear printing, and securely soldered leads.

**Avoid Non-Rechargeable Replacements:** Never solder a standard disposable 3V lithium battery into a float-charge circuit; this can cause severe overheating or even an explosion. Likewise, do not directly substitute it with a non-rechargeable 3.6V lithium-thionyl chloride battery without modifying the circuit. Ensure proper insulation: After soldering, be sure to maintain a safe distance between the battery body and surrounding components; apply insulating paper if necessary to prevent short circuits.

Preserving the device's memory

In an era increasingly dominated by solid-state storage and supercapacitors, the VARTA 3/V200H remains an irreplaceable guardian of memory for countless legacy devices. It employs a gentle, enduring trickle charge to withstand the erosion of time. When you solder this brand-new battery onto a motherboard from thirty years ago—watching it accurately report the time and steadfastly retain calibration parameters upon every startup—the satisfaction of extending the life of such an electronic relic is perhaps the most moving aspect of repair and restoration.

PLC battery 3/V200H For VARTA 3/V200H