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Manufacturer
Model
What This Guide Helps With
Troubleshooting charging failures, battery alarms, unexpected battery operation, or reduced backup runtime caused by AC power, connections, charging conditions, or battery deterioration.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not intentionally disconnect AC power or perform battery-runtime testing while the WATO EX Series is supporting an active patient.
If a battery or power warning occurs during clinical use:
- Notify the anesthesia provider immediately.
- Confirm that ventilation, gas delivery, alarms, and required monitoring remain operational.
- Restore the machine to a verified AC power source when possible.
- Prepare another verified anesthesia machine or approved backup ventilation method.
- Transfer the patient when reliable power or battery operation cannot be confirmed.
Expected outcome: Patient care is not dependent on equipment with uncertain backup-power capacity.
Continue troubleshooting only after the anesthesia machine has been removed from active patient use.
2. Confirm the Reported Battery Condition
Record the exact displayed message, alarm, and battery indication. Determine whether the issue involves:
- Battery not charging
- Battery symbol missing
- Machine unexpectedly operating on battery
- Battery percentage or runtime decreasing while connected to AC
- Battery failing to reach a full charge
- Short operating time after charging
- Immediate shutdown when AC power is removed
- Battery-related startup or self-test failure
Expected outcome: The failure is clearly identified as a charging, AC-input, battery-recognition, or battery-capacity problem.
3. Verify the AC Power Source
Confirm that the wall receptacle is approved for medical equipment and supplying power.
Test the receptacle with an approved outlet tester or another known-good device. Do not rely solely on the receptacle’s appearance or labeling.
Check whether the machine is connected to:
- Normal utility power
- Emergency power
- An isolation-power system
- A power strip or extension device
- A switched receptacle
Whenever possible, connect the anesthesia machine directly to a verified wall outlet.
Expected outcome: The machine recognizes AC power and no longer indicates that it is operating only from its battery.
If the issue is resolved, document the faulty or inactive receptacle and stop troubleshooting.
4. Inspect the Power Cord and Connection
Inspect the AC power cord for:
- Cuts or exposed conductors
- Bent or damaged plug blades
- Loose strain relief
- Burn marks or discoloration
- Damaged insulation
- A loose connection at the machine
- Evidence that the cord has been pulled or crushed
Reseat the power cord firmly at both the wall outlet and the anesthesia machine.
If the cord is detachable and facility policy permits, test with a known-good compatible hospital-grade cord.
Expected outcome: The power connection remains secure and the AC-power or charging indicator remains stable when the cord is gently observed for movement.
If replacing or reseating the cord restores charging, stop and replace the defective cord.
5. Confirm AC-Power Recognition
With the machine connected to verified AC power, check the display and applicable power indicators.
Confirm that:
- The machine does not display an AC-power-loss message.
- The battery symbol shows charging or increasing capacity.
- The AC indicator remains illuminated.
- The machine does not repeatedly alternate between AC and battery operation.
Allow several minutes for the displayed battery status to update.
Expected outcome: The WATO EX Series consistently recognizes external power and begins charging its installed battery.
An unstable AC indication suggests a power-cord, receptacle, inlet, power-supply, or internal charging-system problem.
6. Remove Unapproved External Power Devices
Disconnect the machine from extension cords, nonmedical power strips, adapters, or temporary power devices.
Inspect approved accessory outlets on the anesthesia machine for excessive connected loads. Remove nonessential external equipment according to facility policy.
Do not exceed the manufacturer’s specified auxiliary-outlet capacity.
Expected outcome: The anesthesia machine remains on AC power without intermittent transfer to battery or charging interruption.
If charging resumes after external accessories are removed, investigate the accessory load or power-distribution device before returning the system to service.
7. Allow Adequate Charging Time
Connect the machine to verified AC power and leave it connected for the charging period specified by the applicable WATO EX model’s instructions.
Keep the system in the manufacturer-recommended charging state. Avoid repeatedly disconnecting AC power during this period.
Battery configuration and expected backup time vary across the WATO EX family. For example, published specifications list a built-in lithium-ion battery for the WATO EX-35, while the WATO EX-65 may support different battery quantities and runtimes. Evaluate the exact model and installed configuration rather than applying one runtime to the entire series.
Expected outcome: The indicated battery capacity gradually increases and eventually reaches the expected charged state.
If the battery percentage does not increase after adequate charging, continue troubleshooting.
8. Check Environmental Conditions
Confirm that the machine is being charged within normal room-temperature conditions.
Look for:
- Excessive heat near the rear or lower cabinet
- Blocked ventilation openings
- Storage in a cold loading area
- Recent transport from an unusually hot or cold environment
- Dust accumulation around external vents
- Direct exposure to heating equipment
Allow the machine to reach normal room temperature before evaluating charging performance.
Expected outcome: Charging begins or proceeds normally after environmental conditions are corrected.
Unusual heat, swelling, odor, smoke, or discoloration requires immediate removal from service. Disconnect AC power when safe and follow the facility’s battery-safety procedure.
9. Review Battery Age and Service History
Review the equipment record for:
- Battery installation date
- Previous battery replacements
- Repeated low-battery complaints
- Long periods in storage without charging
- Recent internal service
- Previous liquid ingress
- Unexpected shutdown history
- Failed preventive-maintenance battery testing
A battery may indicate that it is charging but still have insufficient usable capacity due to age, repeated cycling, prolonged storage, or deterioration.
Expected outcome: The battery’s history supports either continued testing or replacement according to the manufacturer’s maintenance requirements.
10. Perform a Controlled Battery-Operation Check
Perform this check only after the machine has passed its normal checkout and is not connected to a patient.
Confirm that:
- Gas supplies and an approved backup ventilation method are available.
- The machine is fully charged according to its indication.
- No unresolved power or system alarms are present.
- The test follows facility policy and the applicable service documentation.
Disconnect AC power briefly and observe:
- Whether the machine transfers smoothly to battery
- Whether ventilation continues
- Whether the battery indicator appears
- Whether the reported capacity immediately collapses
- Whether the machine shuts down or restarts
- Whether unexpected alarms occur
Reconnect AC power promptly.
Expected outcome: The machine transfers to battery without interruption and returns to AC operation when power is restored.
Do not perform a prolonged discharge test without the approved procedure, suitable test conditions, and enough time to recharge the battery before clinical use.
11. Evaluate the Backup Runtime
When authorized, compare measured battery operation with the expected performance for the exact WATO EX model, battery quantity, battery age, load, and test conditions.
Published runtime values generally assume new, fully charged batteries under defined ambient conditions. Actual runtime may be reduced by battery age, installed modules, screen brightness, accessories, ventilation demands, and environmental conditions. The WATO EX-65 specification, for example, lists different expected durations for one-battery and two-battery configurations.
Expected outcome: The measured runtime is reasonably consistent with the applicable manufacturer specification and facility acceptance criteria.
If runtime is substantially shortened, the battery likely has reduced capacity even when the charging indicator appears normal.
12. Restart and Complete the System Checkout
After restoring verified AC power:
- Shut down the machine normally.
- Leave it connected to AC power.
- Restart the system.
- Observe all power and battery indicators.
- Complete the manufacturer-required pre-use checkout.
- Confirm that no battery, charging, or power alarms return.
Expected outcome: The machine starts normally, recognizes AC power, indicates battery charging or adequate capacity, and passes checkout.
If the alarm returns or battery performance remains unreliable, stop troubleshooting and escalate the device.
If the Problem Persists
If the receptacle, power cord, external accessories, charging time, environmental conditions, and basic battery operation have been checked, common external causes have been ruled out.
The likely causes may include:
- A depleted or deteriorated battery
- A battery that is not being recognized
- A defective internal charger
- A damaged AC inlet or internal power connection
- An internal power-supply failure
- Battery-management or communication failure
The device should be:
- Removed from service
- Labeled Out of Service
- Sent for repair or bench evaluation
- Evaluated using the correct Mindray service documentation and approved test equipment
Do not return the anesthesia machine to clinical use solely because it operates normally on AC power. Reliable battery backup is a safety function.
Knowing when to stop and escalate is proper troubleshooting.
Clinical Use Tip
Never test battery runtime on an active patient. Move the patient to another verified anesthesia machine before disconnecting AC power or evaluating backup capacity.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Anesthesia staff reported that the Mindray WATO EX Series displayed a low-battery warning and provided only several minutes of backup operation."
Cause
What was observed during troubleshooting.
Example:
"Verified AC power and the hospital-grade power cord were functional, but the fully indicated battery lost capacity immediately when AC power was disconnected."
Resolution
What action was taken.
Example:
"Removed the anesthesia machine from service, labeled it Out of Service, and sent it for battery replacement and internal charging-system evaluation."
Helpful Details to Include (If Known)
- Exact WATO EX model
- Exact battery or power message
- Battery icon behavior
- AC-power indicator status
- Outlet tested
- Power cord inspected or swapped
- External accessories removed
- Charging time allowed
- Battery installation date
- Starting battery percentage
- Runtime observed
- Whether ventilation continued during transfer
- Unexpected shutdown or restart
- Unusual heat, swelling, odor, or discoloration
- System-checkout result
- Final device status
Final Thought
Battery troubleshooting must protect the patient before proving the failure. Verify external power, connections, charging conditions, and battery behavior logically before suspecting an internal defect. When dependable backup power cannot be demonstrated, remove the machine from service and document the complaint, cause, and resolution clearly.
That is successful troubleshooting.