SwitchBot Lock Ultra: What It Is and How to Use It Safely

The SwitchBot Lock Ultra is a retro-fit smart lock: it fits over the thumb turn on the inside of an existing door lock rather than replacing the lock itself, and it lets you unlock with a fingerprint, a PIN code, NFC, your phone or your voice. SwitchBot lists it as fitting 99.9% of doors, working with most single deadbolts, Jimmy Proof and mortise locks with an adapter, and says the rechargeable main battery lasts around nine months based on 10 locks and unlocks a day¹.

If you are thinking of fitting one, the practical questions are whether it suits your door, how you keep it powered, and how you get in when something goes wrong. The lock carries three layers of power: a rechargeable main pack, a cold-resistant CR123A backup, and an emergency reserve that lets you in when both are nearly flat¹. It is sold in Black and Silver, on its own or in bundles with a keypad, hub or doorbell¹.

This page sets out what the lock does, what it fits, how to fit and calibrate it, how to keep it powered, how to unlock it, and what to do when the battery runs low or the lock sticks. It also covers the safety points that matter with any smart lock, and where to get help if something goes wrong.

What the SwitchBot Lock Ultra is and which doors it fits

The Lock Ultra is a motorised unit that sits over the inside thumb turn of your existing lock. SwitchBot describes it as a smart lock released in 2025, with a full aluminium alloy shell and a body 50% slimmer than the Lock Pro¹. It measures 122 × 62.6 × 66.8 mm and weighs 367 g with batteries fitted¹. Because it turns the existing lock rather than replacing it, you keep your original door lock and cylinder, which matters if your home insurance names a particular standard. Our guide to doors and locks explains what insurers tend to look for.

On compatibility, SwitchBot states the lock fits 99.9% of doors and works with most single deadbolts, Jimmy Proof and mortise locks with an adapter¹. The maker also says the Accessory Kit supports Jimmy Proof and Mortise locks without replacing the lock core, and that the lock is designed for European locks and lets you keep your original door lock³. Mortise locks require the adapter¹. If your door is unusual, check with the maker before ordering.

A smart lock is not right for every door. Which? notes that smart locks are more expensive than traditional locks, need firmware updates, and need an internet connection for features such as remote unlocking⁶. If you rent or share an entrance, our page on smart locks in rented and shared homes covers the questions to ask first, and Smart Locks: How They Work and What to Check sets out the wider picture.

Power: about nine months from the main battery, plus backup and emergency layers

The Lock Ultra runs on three power layers, which SwitchBot calls triple battery protection: main, backup and emergency¹. The main pack is rechargeable and holds three 18350 cells in parallel, 4200mAh in total, and SwitchBot rates it at nine months of battery life based on 10 locks and unlocks a day¹. That figure is an estimate from the maker, not a guarantee: a busy household, a stiff lock or a cold porch will use more.

The second layer is a CR123A backup battery. SwitchBot describes it as low self-discharge and cold-resistant, and says it is the perfect backup for winter travelling or when the main battery is charging³. The maker states the backup supports 500 backup lock and unlock operations². The third layer is a supercapacitor, which SwitchBot says stores just enough power to let you in even when the battery is nearly empty, and a micro-power unlock mode that gathers minimal current for emergency access when both batteries are low³.

For context, Which? says smart lock batteries generally last from six months to a couple of years before they need replacing or recharging⁶. The Lock Ultra's nine-month figure sits inside that range. The National Security Inspectorate, writing about alarm system backup batteries, notes that a backup should keep a system running for at least 12 hours in a power cut⁷. That is alarm guidance rather than lock guidance, but the principle is the same: a backup is there to buy you time to act, not to run indefinitely.

Getting in when the battery runs low or the lock sticks

The first warning comes from the lock itself. SwitchBot states that you get a low battery reminder through the app or on the device, with LED light, app notifications and sound alerts⁵. Treat that first warning as the moment to recharge the main pack. If you ignore it, the lock steps down through its backup and emergency layers rather than stopping dead.

If the lock has stuck, the SwitchBot app has an emergency unlock option, which boosts power before turning the handle². If both batteries are low, micro-power unlocking gathers minimal current to provide just enough power for emergency access, and the supercapacitor holds enough for a few unlocks³. SwitchBot states the micro-power reserve supports five emergency unlocks⁵.

From the inside, the internal dial can always be twisted to lock and unlock the door by hand, and there is a large push button to lock or unlock². That is your fallback if the motor or the app misbehaves: you are not locked in.

One risk worth knowing before you switch on automatic locking: Trusted Reviews notes that locking automatically when the door closes means you run the risk of locking yourself out automatically². If you enable it, make sure a key is reachable from outside.

Works down to , 40°C with a cold-resistant backup battery

SwitchBot states the Lock Ultra works even in extreme cold down to , 40°C³. That figure is the maker's operating range, and it is the backup battery that carries the lock through cold weather: the CR123A is described as low self-discharge and cold-resistant, and as the backup for winter travelling or while the main battery charges³.

In a UK winter, the practical points are these. Cold reduces what a battery can deliver, so a lock on an exposed north-facing door will lean on its backup sooner than one in a sheltered porch. The main pack is rechargeable, so bring it indoors to charge rather than charging it in a cold porch. The lock also supports 5 emergency unlocks on micro-power, so a flat battery does not have to mean a locked-out household³.

If your lock is on an outbuilding, a gate or a door you do not use every day, the same logic applies with more force: a lock that is rarely used gives you fewer reminders, because the app only warns when the lock reports. Check it in person before a cold snap.

Fitting it to your door: adaptors, mounting plates and calibration

Fitting is designed to be drill-free. SwitchBot says no drilling or damage is required and that it installs on your existing door lock in minutes, fixed with screws or adhesive mounting³. The box includes mounting components (bracket, screws and lock cylinder parts), a magnet and three wood grain stickers, a charging cable and support tape, and the rechargeable main pack¹.

SwitchBot provides eight different adaptors designed to fit over the thumb turner, as with the Lock Pro². There are two mounting plates: the A plate has grubscrews to attach it to the lock plate, and the B plate is supposed to stick to the door². Once mounted, the door needs to be held open, and then calibration runs automatically².

Customer reviews on the SwitchBot store give a sense of how it goes in practice. One reviewer said it was very easy to install, with no more than 30 minutes between out of the box and up and running⁵. Another found HomeKit integration took a couple of attempts, and that their thumb turn lock was not on the supported list, but a small modification to one of the adaptors got it set up⁵. If your lock is not on the list, ask SwitchBot support before you start rather than modifying an adaptor on your own initiative.

Ways to unlock: fingerprint, PIN codes, NFC, phone and voice

SwitchBot lists five unlock methods for the Lock Ultra: fingerprint, auto unlock, NFC, voice, or your smartwatch¹. It also states 0.3-second fingerprint recognition supporting up to 100 fingerprints, and an unlock time of 0.3 seconds with 98% accuracy¹. PIN codes can be set as Permanent, Temporary (operating only between set dates and times, with an expiry), One-time, or Emergency, and an email is sent when an Emergency PIN is used². The Touch Combo page describes four password types: permanent, one-time, time-limited and disguise codes⁵.

This is now a common way for smart locks to work. Verisure, a smart lock maker, says models can be operated by PIN code, biometrics such as fingerprints or face recognition, a fob or voice recognition⁸. Aqara lists NFC, custom passcodes, fingerprint recognition, Apple Home Key or Zigbee on its range¹⁰, Nuki lists fingerprints, codes, a fob, a smartwatch or a physical key¹¹, and Burg lists fingerprint, code, smartphone or radio key¹². The point for a household is not which is best but which suits each person: a fingerprint for the adults who come and go, a PIN for a visitor, a one-time code for a tradesperson.

Whatever method you choose, secure the account behind it. Essex Prepared advises using a PIN, password, biometric (fingerprint or facial recognition) or pattern, and says any is better than none¹³. Avon and Somerset Police advise using facial or fingerprint recognition for your phone, digital wallets and banking apps, so you unlock with your face or finger rather than a PIN¹⁴. If your lock is controlled from a phone, that phone is now part of your door security.

Hub, Matter and remote control

Out of the box, the Lock Ultra works over Bluetooth, and SwitchBot states that a SwitchBot Hub is not required for Bluetooth unlocking and local control⁵. A hub is required for remote control via the app, real-time status updates, voice assistant integration, Matter and IFTTT integration, and automation with other SwitchBot devices⁵. The lock is listed as networking over Bluetooth and Wi-Fi, and as Matter compatible with a Matter-compatible hub².

The bundles change what you get. The Vision Pro Combo comprises the Lock Ultra, a Hub Mini Matter and a Keypad Vision Pro, and SwitchBot says the included Matter-supported Hub Mini gives full compatibility with HomeKit, Alexa, Google Assistant and other third-party smart home platforms⁴. The Touch Combo supports Matter and works with Apple HomeKit via the SwitchBot Hub mini, and is also compatible with Alexa and Google Assistant⁵. The Vision Combo includes a Matter-compatible Hub Mini compatible with HomeKit, Alexa and Google³.

One caution on remote access: it depends on your internet connection and your home network. Which? notes that smart locks need an internet connection for features such as remote unlocking⁶. If your broadband or mobile signal is poor, our page on alarms and cameras on a weak signal covers what still works. Ofcom's guidance on the move away from landline calls is relevant if your home still relies on a landline for connectivity¹⁵.

Security, tamper alerts and keeping the account safe

SwitchBot describes a six-layer security system covering tamper alerts, encryption and real-time status for all-around safety¹. The Vision Pro bundle adds AES-128 encryption for stored facial and palm vein data⁴. The Touch Combo page states the app supports two-step confirmation for remote unlocking⁵. Those are the maker's own claims about its own product; they are worth checking against your own arrangements rather than taking on trust.

The weakest point in most smart lock set-ups is not the lock but the account and the phone. The lock offers 4 password types, permanent, one-time, time-limited and disguise codes, so you can give a visitor or a trader a code that stops working after they leave rather than sharing your main one³. If someone can unlock your phone, they may be able to unlock your door.

For the wider picture on choosing and living with a smart lock, see Smart Locks: How They Work and What to Check and Smart Lock or Traditional Key Lock?. If you are weighing up whether a smart lock is worth it at all, Which?'s guidance is a useful independent starting point⁶.

Motor noise, silent mode and living with the lock

SwitchBot lists the Lock Ultra's noise level as 50 to 55dB measured at 50cm, with a no-load speed of 50rpm⁵. It also says the upgraded motor is quieter than the Lock Pro, with noise reduced to under 20dB in Silent Mode⁵. The combos add a night setting: the Touch Combo automatically switches to Quiet Mode at night, disabling sound effects⁵, and the Vision Combo does the same³.

If the lock is on a bedroom door or a door next to one, set the quiet schedule before the first night rather than after. The lock also has a stall torque of 22.5Kgf.cm and a load torque of 8Kgf.cm, which is the maker's way of saying how much turning force it can apply to a stiff lock⁵. A door that needs a shoulder to close will make the motor work harder and drain the battery faster.

Support, warranty and swapping from a Lock Pro

SwitchBot states that all its smart locks come with a 2-year warranty¹. The UK store lists a 30-day money-back guarantee and lifetime customer support, and ships from a local warehouse³. Keep your order confirmation: warranty claims normally need proof of purchase, and the warranty period runs from purchase rather than from fitting.

If you already have a Lock Pro, SwitchBot says both use the same thumbturn adaptors, so it is quite a straightforward swap². You will still need to recalibrate: hold the door open and let calibration run automatically². The Ultra is described as 50% slimmer than the Lock Pro with an all-metal body, so check the new body clears your door frame and handle before you rely on it³.

If a lock develops a fault, contact SwitchBot support before dismantling anything. A lock that is partly disassembled is a lock you cannot rely on, and it may affect your warranty. For the wider question of what to do if you are locked out, our guide to being locked out of your home covers locksmiths and the steps to take.