A 6ES5 980 0AB42 battery board cannot be replaced safely from the S5-110 family name alone. First identify whether the controller is an S5-110A or S5-110S, record the complete CPU order number, and compare the installed board’s electrical and mechanical details with the candidate replacement. Treat the part as a battery-backed module—not automatically as a replaceable bare cell—because the small circuit board may provide connection, protection, or monitoring functions required by the CPU.
Identify the Exact S5-110 Hardware
The S5-110 designation covers more than one controller and CPU arrangement. A replacement listed for another S5 controller, or even another S5-110 variant, is not sufficient evidence of compatibility. Make the selection from the CPU order number and installed battery assembly.
- Keep the PLC energized if the machine condition and site procedures permit it. Removing power before preserving the program can erase battery-backed memory.
- Record whether the controller is marked S5-110A or S5-110S.
- Copy the complete CPU order number, including every suffix.
- Record the installed module number exactly as
6ES5 980 0AB42. - Photograph the board, connector, wiring orientation, mounting points, and all cell markings.
- Determine whether the battery is soldered to the board, clipped into a holder, or permanently encapsulated.
If the CPU label is unreadable, use the rack position, front-panel markings, connector layout, and clear photographs to identify it through official Siemens support or a qualified legacy-controls supplier. Do not select a battery solely because its connector fits.
Why the Battery Board Matters
The backup source maintains volatile memory while normal PLC power is absent. When the source is depleted, disconnected, reversed, or electrically incompatible, a power interruption can cause program loss, retained-data loss, or a restart without the expected machine state.
The installed item is described as a small board supplied as one unit. That distinction matters: the board may be more than a mechanical battery carrier. Before replacing only its cell, trace or inspect the board for series components, diodes, resistors, fuses, monitoring contacts, or other circuitry. Bypassing those elements can change the voltage presented to the CPU, defeat reverse-polarity protection, or invalidate the controller’s battery-status indication.
| Item to match | Why it matters | How to verify |
|---|---|---|
| CPU variant and order number | Defines the intended backup arrangement | Read the CPU and chassis labels |
| Nominal battery voltage | Incorrect voltage can prevent retention or damage circuitry | Read the original cell marking and applicable hardware documentation |
| Battery chemistry | Determines discharge behavior and whether charging is permissible | Read the chemistry marking; inspect the circuit before assuming it charges |
| Polarity and connector pinout | Mechanical fit does not prove electrical compatibility | Document orientation and confirm with a meter |
| Board circuitry | May provide protection, isolation, or monitoring | Inspect both sides of the assembly |
| Dimensions and mounting | Prevents strain, shorts, and enclosure interference | Measure the original assembly and clearance |
Diagnostic Sequence Before Replacement
Separate a failed battery from a failed battery path. A new source cannot correct an open connector, damaged board, corroded contact, broken trace, or faulty CPU backup input.
- Preserve the application using the site’s proven S5 programming and backup method. Save the program and required retained data before disturbing the assembly.
- Inspect the battery and board for swelling, leakage, corrosion, cracked solder joints, heat damage, and loose contacts. Leakage requires controlled cleanup and inspection of nearby conductors.
- Read every marking on the battery and board. Do not infer chemistry or voltage from physical size.
- Measure battery voltage with an appropriate meter while maintaining correct polarity. An open-circuit reading alone does not demonstrate useful capacity, but a missing or severely depressed reading identifies an immediate problem.
- Confirm continuity through the connector and any accessible protective components. De-energize and isolate the circuit before resistance or continuity measurements.
- Check whether the PLC reports a battery condition and whether the indication changes after installing a known-compatible assembly.
If the battery measures normally but the PLC still reports a backup problem, inspect the board-to-CPU path. If the indication clears but memory still disappears after a controlled outage, investigate the memory configuration and CPU retention circuit rather than repeatedly replacing batteries.
Select and Install the Replacement
The preferred replacement is an assembly explicitly matched to the exact CPU order number and the function of 6ES5 980 0AB42. Because the original board may be discontinued, practical routes include verified legacy stock, professional refurbishment of the original assembly, or a documented engineered replacement. Age matters with legacy stock: an unused battery can still have lost capacity during storage.
- Confirm compatibility in writing from official Siemens support documentation or a supplier that identifies the exact CPU and module.
- Match voltage, chemistry, polarity, connector pinout, board function, dimensions, and mounting.
- Back up the PLC program and record operating data needed for recommissioning.
- Follow the CPU-specific procedure for maintaining memory during exchange. Do not assume the board can be unplugged with power removed without losing the application.
- Mark the old connector orientation before removal and prevent exposed conductors from contacting the chassis.
- Install the replacement without pulling on wires or stressing an aged connector.
- Inspect polarity again before making the final connection.
- Dispose of the removed battery according to its marked chemistry and site rules.
Do not install a rechargeable cell unless the original circuit and documentation identify a rechargeable system. Likewise, do not substitute a primary cell into a circuit that applies charging current. The deciding measurement is the current and voltage at the battery connection under the controller’s normal operating states, interpreted against the specified battery chemistry.
Verify Retention Without Risking the Machine
Verification must prove both battery recognition and actual memory retention. Perform the test during a controlled maintenance window with the machine secured against unexpected motion.
- Confirm that the PLC enters its expected operating state after installation and that no battery indication remains.
- Compare the online program with the saved copy where the available S5 tools support comparison.
- Record critical retained values before the test.
- Apply the documented power-down procedure, wait only for the site-approved test interval, and restore power.
- Verify the program, operating mode, retained values, outputs, interlocks, and machine sequence before returning equipment to service.
If retention fails, restore from the verified backup and test the battery voltage at the CPU connection. A good battery measured at the board but not at the CPU points to the connector, board circuitry, or internal retention path.
Recurring Replacement Pitfalls
The most common error is treating all S5 backup batteries as interchangeable. Similar packaging does not establish the correct voltage, chemistry, pinout, or board function. Other recurring failures include buying old stock without checking its condition, reversing a two-wire connector, soldering directly to a cell that is not supplied with suitable tabs, and powering down before securing a restorable program backup.
A field-fabricated substitute also needs secure insulation and strain relief. Loose cells or exposed terminals can short against the enclosure. Label any engineered replacement with its voltage, chemistry, polarity, installation date, and the CPU for which it was qualified so the next maintenance action does not repeat the identification work.
FAQ
What replaces the Siemens 6ES5 980 0AB42 battery board?
Select the replacement by the complete S5-110 CPU order number and by matching the original board’s voltage, chemistry, polarity, connector, and circuitry. The module number alone does not establish a safe current substitute.
Can I replace the cell on an S5-110 battery board?
Only after identifying the cell specification and confirming what the board circuitry does. Preserve the original protection and monitoring path, and use a qualified battery service when the cell is soldered or permanently assembled.
Will an S5-110 lose its program when I change the battery?
It can lose battery-backed memory if both normal power and the backup source are absent. Save and verify the program first, then follow the CPU-specific exchange procedure that maintains memory during replacement.
Why does the S5-110 still show a battery problem after replacement?
Check polarity, connector continuity, corrosion, board components, and voltage at the CPU-side connection. If voltage reaches the CPU but retention still fails, investigate the CPU backup input and memory configuration.