Hue accessories run on batteries, so power problems are battery problems. The motion sensor takes two AAA batteries, which independent guides say last about two to three years, and replacing them means removing the back cover with a small screwdriver, inserting two new AAA cells with correct polarity and refitting the cover. The dimmer switch uses a coin cell: guides say some models use CR2450 and others CR2032, and they are not interchangeable, so check the type printed on the old battery before buying.
The checks in more detail
Open the back of the dimmer gently, note the positive side and insert the new cell. Hue's dimmer reset article advises making sure the battery is installed and working before any reset and notes many wireless dimmer problems such as delayed responses or flickering LEDs are caused by low voltage and not software. If a battery drains in days, look for a cause: a sensor that triggers constantly because of a heat source or a pet will drain quickly, and weak Zigbee signal makes radios work harder.
Use quality batteries, not cheap ones, since low-grade cells can drop below the voltage the accessory needs. Remove batteries from an accessory you will not use for months. A sensor that has just had fresh batteries but stays dead may need a soft reset or re-pair. Date each battery with a marker when you fit it so you know its age at the next fault. Store spare batteries at room temperature and swap sets together. Dispose of old batteries at a collection point.
Rechargeable AAA cells run at a slightly lower voltage than alkaline and some sensors report low battery early with them, so if you use rechargeables, expect earlier warnings and swap them on schedule. Independent guides say the motion sensor should last two to three years on two AAA cells, so a sensor that dies in months has a cause, and finding it, such as a heat source or a weak signal, is better than replacing batteries repeatedly.
Differential
Likely causes of “Hue accessories has power or battery problems”, and how to tell them apart
- 1
Weak AAA batteries
What separates it The sensor stops reporting because its AAA batteries have become weak
How to confirm Replace both AAA batteries with fresh ones and check the sensor responds again
- 2
The wrong coin cell
What separates it The dimmer will not power up because the wrong type of coin cell battery was fitted
How to confirm Use the type printed on the old cell, since dimmers use different coin cells by model
- 3
Constant triggering
What separates it Batteries drain in a few days because something is triggering the sensor constantly
How to confirm Fix the trigger source, such as a heater, a pet or sunlight, that keeps setting it off
- 4
A weak Zigbee link
What separates it Batteries drain faster than expected because the accessory has a weak link to the Bridge
How to confirm Move the accessory closer to the Bridge so it does not spend power retrying the connection
- 5
A corroded contact
What separates it The power comes and goes because the battery contacts have corroded
How to confirm Clean the contacts carefully and refit fresh batteries, checking for any leaked residue
Before you touch a setting
Record this first — changing settings destroys the evidence
- The battery type that the accessory uses
- The age of the batteries and when they were fitted
- How often the accessory is triggered each day
- How far the accessory is from the Bridge
Try in this order
0 of 7 completedIdentify the battery type
ReversibleIdentify the battery type, which is printed on the old cell or inside the compartment, before you buy replacements.
Open the back cover
ReversibleOpen the back cover, using a small screwdriver where the cover is fixed, and take out the old batteries carefully.
Insert fresh batteries
ReversibleInsert fresh batteries the right way round, matching the polarity marks, so that the contacts touch firmly.
Refit the cover
ReversibleRefit the cover and test the accessory, by moving in front of the sensor or pressing a button on the dimmer.
Check what triggers it
ReversibleCheck what triggers the sensor, such as heat, pets or sunlight, and move it if it keeps firing for no reason.
Move it closer
ReversibleMove the accessory closer to the Bridge if the signal is weak, since a weak link makes the batteries drain faster.
Contact Hue
ReversibleContact Hue if the accessory stays dead after new batteries, and tell them the model and battery type.
Model-specific
What is true of this model and not of its siblings
- Motion sensor
- Two AAA batteries.
- Dimmer
- A coin cell; check the type.
Stop boundary
When this stops being a self-service repair
- !If fresh batteries do not help, contact Philips Hue support
- !If batteries drain very quickly, look for what keeps triggering the accessory
- !If a battery has leaked, clean the compartment carefully before fitting new batteries
Evidence ledger
Sources behind this answer
Battery type and life.
Dimmer battery.
Soft reset and factory reset.
Motion sensor features.
The company and its products.
Exact questions
Common questions
What batteries does the motion sensor use?+
The Hue motion sensor uses two AAA batteries, which you can buy in any shop and fit behind the cover.
How long do they last?+
The batteries last about two to three years in normal use, though a busy sensor drains them sooner.
What does the dimmer use?+
The dimmer uses a coin cell, which is a CR2450 or a CR2032 depending on the model.
Are they interchangeable?+
No, the coin cells are not interchangeable, so use the type printed on the old cell or inside the compartment.
Why do batteries drain fast?+
Batteries drain fast when the accessory is triggered constantly, for example by heat or by a pet.
Can a weak battery cause odd behavior?+
Yes, a weak battery can cause odd behavior, such as missed detections, delays or a sensor that keeps dropping offline.
Should I use quality batteries?+
Yes, use quality batteries, because cheap ones can leak or run out early and cause the same faults again.
How do I soft reset a dimmer switch?+
Hold all four buttons for about five seconds, which restarts the switch without removing it from the Bridge.
How do I factory reset a dimmer switch?+
Hold the setup button on the back for about ten seconds, until the LED blinks, to return it to factory settings.
What does the dimmer LED show after reset?+
After a reset the dimmer's LED blinks orange, showing that it is ready to be set up again.
Where is the setup button?+
The setup button is on the back of the dimmer switch, and you hold it to reset or pair the switch.
How do I contact Hue?+
Contact Hue through the Philips Hue support site, where you can find chat and phone contacts.