Litter-Robot 4: only the power button blinking blue, no full light bar?
- Full light bar gone: the usual solid blue light bar on the control panel has disappeared.
- Only the Power button blinks blue: that single LED keeps flashing at reduced brightness while the rest of the panel stays dark.
- WiFi and night light are unresponsive: the Whisker app shows the unit offline and the night light does not turn on, even though the globe still rotates through cleaning cycles.
- This is not a malfunction: a blinking-only Power button means your Litter-Robot 4 is running on its optional Backup Battery after a power interruption.
- WiFi and the night light shut off on purpose to conserve battery power — the cleaning cycle itself keeps working.
- Everything returns to normal automatically once household power is restored; no reset is required.
- No Backup Battery installed? Then this exact symptom means something else — check the power cord and outlet first.
Why only the power button is blinking
This is the expected behavior of the optional Backup Battery, not a fault code. If your Litter-Robot 4 has this $40 accessory installed inside the base, the unit is designed to keep running quietly through short outages instead of shutting down mid-cycle.
Power interruption triggers battery mode
Whisker's official installation guide states that when power is interrupted, the unit automatically switches to Backup Battery Mode: the control panel light bar goes from full blue to only the Power button LED flashing blue, at roughly 50% of normal brightness. The globe keeps rotating and cleaning on schedule — only the display and connectivity change.
WiFi and night light shut off on purpose
WiFi and the automatic night light are deliberately disabled during Backup Battery Mode to conserve energy, so the Whisker app will briefly show the unit as offline. This is expected and does not indicate a network problem to troubleshoot.
In most cases, nothing needs to be done: once household power comes back, the light bar returns to full blue, WiFi reconnects, and the battery begins recharging on its own.
Locate and check the Backup Battery
Follow these steps if you want to confirm whether a Backup Battery is installed, or to install one for the first time. Work through them in order.
Don't have a Backup Battery yet?
The official Whisker Backup Battery (UB1213k, 24-48h runtime) installs in about 15 minutes with just a Phillips-head screwdriver.
If the issue persists: replacement options
If the light bar stays dark with only the Power button blinking even while the unit is plugged into a confirmed working outlet, and no battery is present in the pocket, the Backup Battery itself is the missing part — not a defect to repair.
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If you already have a battery installed and the symptom doesn't clear once power returns, move on to the advanced checks below.
Advanced troubleshooting
Use these scenarios to rule out other causes before assuming a defective battery.
No Backup Battery installed, but the panel still went dark
Without the optional Backup Battery, a Litter-Robot 4 has no way to stay on through an outage — the unit simply shuts down completely and the panel goes fully dark, not just partially. If the Power button is blinking at all with no battery installed, check the power cord connection at both the wall outlet and the unit, and try a different outlet before contacting support.
Don't confuse this with the Drawer Full Indicator or WiFi reconnect blink
Whisker documents two other blue-blinking states on the Litter-Robot 4 that look similar but mean something different. A flashing blue full light bar is the Drawer Full Indicator (DFI): it means the waste drawer needs emptying, and pressing Reset then Cycle clears it. A blinking blue light bar shown alongside a WiFi icon in the app means the unit is reconnecting to your network. Backup Battery Mode is the only one of the three where the full light bar goes dark and only the single Power button LED blinks.
Battery installed but not recharging after power returns
The battery recharges automatically once the unit is connected to mains power again — this is not a manual process, and Whisker does not publish an exact recharge duration. If the light bar never returns to solid blue after a confirmed working outlet and a reasonable recharge window, the sealed lead-acid cell (UB1213k) may have reached end of life and should be replaced.
| Light behavior | Meaning | Action |
|---|---|---|
| Only Power button blinks blue, rest of bar dark | Backup Battery Mode (power interruption) | None needed — resumes automatically when power returns |
| Full light bar flashing blue | Drawer Full Indicator (DFI) | Empty waste drawer, then Reset + Cycle |
| Light bar blinking blue + WiFi icon in app | Reconnecting to WiFi | Confirm app is updated and unit is plugged in |
| Entire panel dark, no battery installed | No power reaching the unit | Check cord and outlet |
Frequently asked questions
Does the Litter-Robot 4 still clean normally in Backup Battery Mode?
Yes. The cleaning cycle continues to run on its usual schedule; only the WiFi connection, the night light, and the control panel's light bar are affected to conserve battery power.
How long does the Backup Battery last during a power outage?
Whisker estimates 24-48 hours of runtime, based on roughly 10 cleaning cycles per day. Actual time will vary with how often your cat uses the unit.
Why doesn't WiFi reconnect right after the power comes back on?
WiFi is intentionally disabled during Backup Battery Mode and should reconnect automatically within a few minutes once the unit is back on household power. If it doesn't, confirm the Whisker app and unit firmware are both up to date.
How do I check whether my unit already has a Backup Battery installed?
Open the bonnet, remove the globe, and take off the four screws on the motor cover to look inside the battery pocket — no tools beyond a Phillips-head screwdriver are needed.
Conclusion
Seeing only the Power button blink blue can look alarming the first time it happens, but for most Litter-Robot 4 owners it simply means the optional Backup Battery is doing its job during a power interruption. Once you know what to look for, telling this apart from a real fault takes seconds. Let us know in the comments if this cleared things up for you!
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