Can you buy second-hand smart devices? I picked up about ten items and two went wrong, and the camera wasn't unbind, so my ex can still see your place

Last year, I bought four second-hand routers on Xianyu—the CR8809 and Redmi AX6000—and once I got the hang of them, I thought smart devices could just follow the rules. Since the beginning of this spring, I've received about ten items, two of which went wrong, and almost fell into a pitfall I never dared to imagine. Only then did I realize that the rules for second-hand smart devices are different from those for routers—once the router is restored from the factory, it's clean, while a smart device is something tied to the Seller Cloud account.

first mention the bottleneck: account binding, not machine

the router, hold down the reset button, and clear your broadband account and password cleanly, just like on a new device. I wrote about second-hand router inspections, mentioned the ESET report. The biggest risk for second-hand network equipment is data residue; resetting it basically solves the problem.

smart devices don't fall for this. The first thing you get is to bind the Mi Home account—the sensors, cameras, and speakers of the Mi Home—so the device is 'owner' in the cloud. Once you receive the goods, install the battery, power on, open your Mijia app and click 'Add'. Nine times out of ten, a line of text appears: The device has been bound to another account.

untie, there are only two paths. First, find the seller and have them enter the device page in their Mijia app, tap the three dots in the top right corner, scroll down to delete the device, and the cloud will automatically reset it. You can add it immediately—so face-to-face transaction, immediate unbinding, immediate binding, and payment after binding, none of these steps can be skipped. Second, if the seller goes missing, call Xiaomi customer service at 400-100-5678, provide a screenshot of the Xianyu order or similar purchase proof, and after verification, the customer service remotely unbinds the binding. I walked the second path on my friend's behalf once, waited three days before it was unlocked, provided you could keep the order record. Avoid those paid 'remote unbinding' third-party services online—account security is not guaranteed.

two failures: one bricked, one battery

first item is a gimbal camera, 45 yuan. The seller confidently said it had been restored and left the factory. When I got it, I scanned the code to add, but it popped up 'The device has been bound to another account.' I went back to the seller, but they said the account had already been canceled and couldn't be recovered. The machine itself is fine; when powered on, it switches to a gimbal but can't access my account. It sat on the bookshelf as a decoration for two months, and finally sold for 30 yuan. Later, after browsing more on Xianyu, I realized that the camera-linked camera is everywhere. The seller, wanting to save trouble, only pressed the reset button on the device and didn't delete the device in the app. The cloud "owner" was still there.

camera adds another issue that other brands don't have: it has eyes. my post about self-checking camera privacy I've checked the methods of black market trafficking. If the second-hand device isn't fully unbind, the previous owner's account should theoretically still be able to see footage of this machine. Installing a camera of unknown origin in the bedroom is like leaving a window for strangers. So when it comes to cameras, doorbells with cameras, and peepholes, I only stick to two principles: either unbind and verify in person, or just buy new ones—these are brand new for just over a hundred yuan, so there's no need to gamble.

the second failure was the Roborock G10 that Old Sun bought from the neighboring shop. In 2021, a machine sold for 3999 yuan, while Xianyu sold for 400 yuan—it looked really appealing. The seller said a full charge could sweep the entire house with two wheels and still had some leftovers. In actual tests, it recharged in 58 minutes—the new machine claims 150 minutes of battery life, but it has a 60% degradation. You can't tell by how the battery looks, and the seller's claim of "battery health" is not to be taken seriously. Later, Old Sun spent 89 yuan to replace it with a compatible battery, and with the machine, the total came to 489 yuan. It was still worth it, but the hassle was on my account. Besides batteries, vacuum cleaners also have consumables: roller brushes, side brushes, and filters are all worn parts. Discontinued older models have hard spare parts, so before ordering, search for consumables of the same model on Taobao. If you can't find any, just skip it.

One thing

never touch: Smart door locks

once had a fancy for a semi-automatic door lock, and the seller offered 80 yuan, saying they were moving to a new home and upgrading to a smart whole house. I made plans to pick up myself, but I took the tape measure with me, squatted at their doorstep to look, and in the end didn't dare ask for it.

door locks are security components, and second-hand locks are deeper than cameras. First, most of the management passwords, recorded fingerprints, and NFC cards set by your ex can be removed after factory reset, but how do you confirm they're clean? Second, mechanical keys may have been used several times, and you never know who holds the keys. The third point that makes me most uneasy: the key to the lock cylinder may have been copied . The original key is yours, but the key shop only costs five yuan each. Who knew this lock had served several owners. I wrote about how to choose a door lock I said the lock cylinder is the final bottom line, and second-hand lock cylinders are like those that have been touched by others.

really want to buy it, that's fine. Buy it and replace it with a C-grade lock cylinder, about a hundred yuan. Adding to the wear on the motor and clutch, it's impossible to inspect, so it's better to just buy a new semi-automatic and get a deal under 300 yuan. The money saved on door locks is disproportionate to the anxiety you carry.

closed your eyes to the sensors, especially the Zigbee series

the downfall is one thing, but what let me taste the benefits was the second-hand ones. The Mijia body sensor was brand new for 49 yuan, Xianyu for 20 each, and I bought three in one go; Temperature and humidity sensors 25 each, two of them were collected; Water leakage sensor 15. It has been running under my home IoT private network for over half a year, and not a single one has failed.

the sensor dares to close its eyes and take it in, there are some rules. Zigbee sensors aren't bound to Mijia accounts; they are linked to gateways—Zigbee system sensors are just sub-devices of gateways. Got a second-hand one, long-pressed reset button for five seconds to enter pairing mode, and my own gateway was instantly absorbed. The relationship with the previous owner was completely cut off, with no cloud deadlocks.

the only consumable for these types of devices is button batteries. The CR2450 costs three yuan each, so you can replace it yourself, regardless of how new the device is. Inspection is also straightforward: once you pair it next to your gateway, any reaction is good, and you'll see the outcome on the spot. There's no room for disputes like "finding out it's defective when you go back."

the gateway itself can also be accepted. I also received a second-hand multi-mode gateway to use as a base for Old Sun's smart device—his router was just replaced last year, and he's learning to use it on the sensor. The gateway requires binding the account, but unbinding means deleting a device from the seller's app, done in five minutes in person. The gateway has no camera or microphone, so privacy is clean. the article about central gateways I wrote that Mijia's gateways can be configured with master-slave structures, and second-hand slave gateways cost half as much as new ones.

the middle ground: Manage speakers and small parts yourself

Xiaoai Speaker Mini, bought for 35 yuan, added a voice input for my parents' home. Unbinding the speaker is easy; sellers can delete the device, add the device to the device, and press the long press to reset it. If you want to talk about details, the speakers come with microphones, theoretically...... Forget it, at 35 yuan, I didn't hesitate. The new one costs 149, and the money saved is enough to buy three more sensors. If you really care, restore it to the factory first once you get it. Don't leave it by the bedside or in the living room.

small transmitter-side accessories like wireless switches and buttons are easy to accept. Just reset and pair Zigbee for 20 yuan each, and you can stick them by your bedside or entryway without worry. But for a big item like a robot vacuum, account management is easier — maps and cleaning records are stored locally, reset and cleared from the factory, and the local capability to scan even the internet is off means it doesn't have cloud deadlocks; the bottlenecks are always batteries and consumables, so you have to settle accounts with the previous section before you buy them.

checklist for the actions on the day of receiving the goods

I accepted about ten items, and I solidified my actions into a checklist. Following them basically didn't cause any problems:

• before ordering, ask 'Are you bound to your account?'—If your answer is vague, don't talk at all
• If you can do it face-to-face: unbind, link to your account, pay, complete these three steps together, then
• pair the sensor face-to-face. If it doesn't match, it's broken. There's no other possibility
• run the vacuum cleaner face-to-face for ten minutes, check the meter to see how long it takes to find a charging station. HTML73__
• only accepts sensors and small items for shipping. Don't bet on the camera locks for courier
• keep a screenshot of your order. If the card is bound, contact customer service. The voucher is the

my conclusion is simple: the cheaper the price, the more you dare to accept it; the more expensive, the more you have to avoid those who have eyes or gates. A 20-yuan sensor is broken and thrown away without regret; a 400-yuan robot vacuum is frustrating if you lose a gamble; a door lock for 80 yuan is a gamble and you can't sleep. How do you remove old cameras from the cloud after phased out I wrote an article about it, and the reverse applies to second-hand cameras—the rule in this industry is always to get through the account first, then discuss the machine's condition.