Repair of the battery vacuum cleaner Xiaomi with their own hands

Declining the autonomy of a robotic assistant is a common problem that smart tech owners face after a year or two of active use. Xiaomi vacuum cleaners are famous for their reliability, but lithium-ion batteries do not have a lifespan comparable to the life of the device itself. When the life drops from 90 minutes to 10-15, and the device is constantly lit with an orange indicator, this is a sure sign of the degradation of cells inside the battery pack.

Instead of buying a new expensive module in the official service, many enthusiasts prefer to rebuild the battery themselves, a process that requires accuracy, a minimum set of tools and an understanding of the principles of operation of the BMS (Battery Management System).In this article, we will discuss a step-by-step algorithm of actions that will return your Xiaomi Mi Robot Vacuum or Roborock to its original capacity and extend the life of the gadget for several years.

It is worth noting that self-interference with electronics always carries certain risks. Incorrect soldering or polarity violation can lead to failure of the charge controller or even fire. However, if you are willing to follow safety precautions and follow the instructions clearly, battery recovery is a cost-effective and technically interesting process, available even for beginners in electronics.

Diagnosis and definition of malfunction

Before disassembling the device, you need to make sure that the problem lies in the physical wear of the cells, not in software failure or contamination of contacts. Often users mistakenly sin on the battery when the robot simply can not charge due to the oxidation of the conductive plates on the bottom panel. Carefully wipe the contacts with dry cloth and check if the charging indicator lights up when installed on the base.

If visual cleaning didn't work, you should look at software diagnostics. Mi Home or specialized Android utilities can show the current voltage and battery status. The alarming signal is a sharp jump in the percentage of charge: for example, the robot is running, shows 40%, and then instantly turns off or falls to 5%. This is a classic sign that one or more cells in the assembly have a critically low capacity.

⚠️ Warning: If the battery is swollen, damaged or emits foreign smells, it is strictly forbidden to operate it. These batteries are subject to heat acceleration and can ignite at any time.

To do a deeper test, you can use a multimeter. Measuring the voltage at the output of the main battery connector (usually 14.4V or 21.6V for Xiaomi models), you can estimate the overall build condition. If the voltage is significantly lower than the nominal one (for example, below 12V for 14.4V battery) even after a long charge, this indicates a deep discharge or failure of individual elements, in which case you can not do without opening and replacing cells.

Necessary security tools and measures

You can't have a good repair without the right equipment and the right workspace, you don't need a professional lab, but a basic home craftsman's kit is a must, and the rule of thumb is the safety of lithium batteries, which, if shorted, can release tremendous energy.

The main tool for connecting new elements is spot welding. It is highly recommended not to solder lithium-ion cans with a conventional soldering iron, since overheating can damage the internal structure of the electrolyte and reduce the life of the new battery. If there is no spot welding, you can use a powerful soldering iron with acid flux, but you will have to act very quickly and carefully.

• 🛠️ Tools: screwdrivers (cross and flat), plastic blade for opening the body, bogocreas, tweezers, multimeter.
• 🔋 Consumables: new 18650 battery cells (only original, for example, Samsung, LG, Sony), nickel welding tape, insulation (fiberga, cardboard).
• 🧤 Protection: safety glasses, gloves, non-combustible substrate for the desktop.

Pay special attention to the selection of new elements. There are many counterfeits on the market labeled 3000 mAh or 4000 mAh, which actually have a capacity of 1000 mAh. Buy cells only from trusted suppliers or remove them from serviceable laptop batteries. Xiaomi vacuum cleaners usually require an assembly of 10 or 12 cells connected by 5S2P (5 sequentially, 2 in parallel) or similar.

Battery unit disassembly process

Disassembling the battery of the Xiaomi vacuum cleaner is a step that requires composure. Battery cases are often assembled on latches and glue pads, which harden over time. Do not use excessive force to avoid damaging the plastic case into which the new assembly will be inserted.

First, you have to remove the module from the vacuum cleaner, which is usually fixed by several screws under rubber plugs or clips, and after removal, inspect the top cover, which is held on screws hidden under a specification sticker, and in other cases, you have to carefully cut the body at the seam.

Inside, you'll see a BMS controller board soldered over a cluster of cylinders. The controller is responsible for balancing the cells, protecting against overload and controlling temperature. Our job is to unplug the board without damaging the tracks and electronic components. To do this, gently snack on the nickel lintels that connect the cells to the board's contacts, or sell them off if the design permits.

⚠️ Attention: When the charge is turned off BMS Try not to close the circuit boards between you. While the board is connected to the cells, it's under voltage. Use dielectric tools and isolate the contacts immediately after disconnection.

Once the electronics are turned off, you can remove old cells, they are often planted on glue or fixed with plastic holders, carefully remove old elements, trying not to deform the seats, clean the insides of the housing of residual insulation and glue, so that the new assembly is firmly and without distortion.

Selection and preparation of new cells

The key to a successful repair is to match the components, so you can't mix old and new cans, or cells from different manufacturers or lots, and the difference in internal resistance and capacity will cause the assembly to fail quickly and the controller to balance the charge incorrectly.

Before assembly, be sure to run a charging-discharge cycle for each new cell separately, which will allow them to equalize their voltage and make sure of the real capacity. Use a smart charger (for example, LiitoKala or Opus), which will show the exact values. For a vacuum cleaner Xiaomi optimally use cells with high current (High Drain), since the robot consumes significant current when running the turbobrush.

It is important to observe the orientation of the elements. In the original builds of Xiaomi, the plus leads are often pointed one way or have a specific layout for ease of mounting the board. Gather a new group by following the original connection scheme. This is usually a spike of pairs of cells (2P), which are then connected in series (5S).

Assembly and welding of the battery

The process of connecting the cells requires care. First, assemble the entire group in a plastic holder or fasten them with a shrink/scotch so that they do not shift during welding. Then cut the nickel tape of the desired length. The tape should fit tightly to the contacts of the cells.

When using spot welding, it's important to set the current and the pulse time correctly. Too weak a pulse won't weld the tape, too strong a pulse will burn the jar, do test welding on unnecessary elements, weld the tape first to one side of the cell group, then flip it over and weld it to the other, keeping polarity.

If you use soldering, get the contacts with the minimum amount of solder and hold the soldering iron for no more than 2-3 seconds. Be sure to let the cells cool between soldering contacts. After connecting all the elements, check the total build voltage with a multimeter. It should correspond to the nominal value (for example, about 18-20V for a fully charged 5S assembly).

After_successful_ Connect all elements, set a fee BMS Carefully solder or weld the board pins to the corresponding pins of the nickel tape. It is critically important not to confuse the plus and minus of the overall assembly, otherwise the controller will burn instantly.

Testing and first launch

The final step is to put the refurbished battery in the vacuum cleaner body. Don't twist the screws right away, check the device first. Put the module in the compartment, make sure the contacts are aligned. The vacuum cleaner should make a welcome sound or light up with indicators.

Connect the robot to the charging station. The indicator should light up in orange to signal the charging process. If a red light or an error flashes, immediately turn off the device and check the connections. BMS due to an error in the assembly or a deep discharge that requires a "push" charger.

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After the first charge, allow the vacuum cleaner to fully discharge in quiet cleaning mode, and then recharge fully again, which will help the controller calibrate the capacity readings and correctly display the percentage of charge in the application.

Run a test cleaning through the app. Pay attention to the behavior of the robot: it must confidently leave the base, not go into error after 5 minutes and correctly return to charging. If everything goes well, you can lock the battery cover with screws and enjoy renewed autonomy.

⚠️ Attention: In the first few charging cycles, keep a close eye on the battery pack temperature. 40-45 Excessive heating indicates high internal resistance or balance problems.

Frequently Asked Questions (FAQ)

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The secret to success is not to skimp on cells. A cheap battery will kill time spent repairing and can damage the vacuum cleaner's electronics.