Disassembling a laptop battery: detailed instructions for beginners and professionals

A laptop battery is one of the most vulnerable components, which loses capacity over time and requires replacement. However, buying a new original battery can cost a lot of money, especially for models Apple MacBook, Dell XPS or Lenovo ThinkPad. An alternative solution is to disassemble the battery and replace the failed elements (18650 or 21700) independently. This will save up to 70% of the cost, but requires accuracy and knowledge of the nuances.

In this article we will look in detail at how to properly remove the battery, avoiding short circuits and damage to the controller. You'll learn what tools you'll need, how to identify faulty jars, and what to do if the battery swollen or started to get warm when charging. The instructions are suitable for most modern laptops, but please note: battery design varies by brand HP, Asus And Acer may vary.

Preparing for Disassembly: Tools and Safety Precautions

Before you start disassembling, make sure you have everything you need. An ordinary screwdriver will not help here - you will need specialized tools. Here is the minimum set:

• 🔧 Plastic picks (or guitar picks) - for neatly separating glue seams.
• 🔨 Hot air station (hair dryer) - to soften the glue (temperature 60–80°C).
• 🔪 Knife with thin blade or a scalpel - to pry off the lid.
• 🛠️ Multimeter - to check the voltage on the banks.
• 🧤 Nitrile gloves — protection against possible electrolyte leaks.
• 🔋 Insulated connectors - to temporarily disconnect the battery from the laptop.

Pay special attention to safety. Lithium-ion batteries may ignite if mishandled. Work on a non-flammable surface (such as ceramic tiles), keep it handy Class D fire extinguisher (for metals) or sand. Never disassemble the battery if it:

• 🔥 Swollen (visible by the deformed body).
• 💥 Has traces of oxidation or electrolyte leaks.
• 🌡️ Heats up above 50°C in a calm state.

⚠️ Attention: If the battery has already begun to emit gas (a hissing sound is heard), immediately leave the room and do not try to disassemble it. The risk of explosion in this case is extremely high.

Step 1: Removing the battery from the laptop

The first stage is to carefully disconnect and remove the battery. In most laptops, the battery is secured with screws and double-sided tape. Algorithm of actions:

1. Turn off your laptop, unplug the charger, and turn it over.
2. Remove the bottom cover (a screwdriver may be required Phillips #00 or Torx T5).
3. Locate the battery - it usually takes up up to 50% of the internal space.
4. Disconnect the power cable from the motherboard (pull the plastic tab, do not pull the wires!).
5. Unscrew the screws securing the battery (they may be hidden under stickers).
6. Pry the battery with a plastic pick, carefully separating it from the case.

For some models (for example, MacBook Pro 2015–2017) the battery is glued to the aluminum case. In this case:

Heat the case with a hairdryer (60-70°C) for 2-3 minutes|

Pry up the battery in the corner with a plastic pick|

Do not use excessive force - risk of damaging the controller|

Use isopropyl alcohol to remove adhesive residue

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If the battery does not budge, do not try to pull it out - this may damage it. BMS board (battery management system). It is better to reheat the problem areas with a hairdryer.

⚠️ Attention: In laptops Lenovo Yoga and some HP Spectre the battery can be integrated into the housing. In this case, disassembly requires complete removal of the rear panel and disconnecting additional cables.

Step 2: Disassemble the battery case

The battery case usually consists of two plastic or metal parts glued or soldered together. Your task is to separate them without damaging the internal elements. Disassembly methods:

Housing type	Tool	Disassembly technology	Risks
Plastic (adhesive)	Mediator, hair dryer	Heating up to 70°C + gentle prying around the perimeter	Damage to cans with a knife
Metal (soldered)	Soldering iron 60W, solder	Seam sealing at corners	Short circuit due to inaccurate soldering
Combined (glue + latches)	Mediator, screwdriver	Bending the latches + heating	Broken latches due to excessive force

For plastic housings (e.g. batteries Dell Latitude):

1. Heat the seam around the perimeter with a hairdryer for 1-2 minutes.
2. Insert the pick into the slot and slowly move along the body, separating the halves.
3. If the case does not give in, reheat the problem areas.

For metal cases (found in Apple and some MSI):

• 🔥 Use a soldering iron with a thin tip and a temperature of 300–350°C.
• 🛠️ Start unsoldering from the corners where the attachment points are usually located.
• ⚡ After unsoldering, check with a multimeter that there is no short circuit between the banks.

Step 3: Diagnostics of cans and controller

After opening the case you will see:

• 🔋 Lithium ion banks (usually 4–6 pieces, marking 18650 or 21700).
• 📱 BMS board (charge/discharge controller).
• 🔌 Thermistor (temperature sensor).
• 🔗 Connecting wires (often soldered to cans).

First of all, check the voltage on each bank with a multimeter. Normal indicators:

• 🔋 3.7–4.2V - the bank is working properly.
• 🔋 2.5–3.6V — discharged, but subject to restoration.
• 🔋 0–2.4V - deep discharge, requires replacement.
• 🔋 0V - short circuit inside the can (dangerous!).

If the voltage on the banks is very different (for example, one shows 4.1V, and the other - 3.2V), this indicates imbalance. In this case:

1. Disconnect the BMS board (take a photo of the connection diagram first!).
2. Charge each jar separately using lithium ion charger (For example, TP4056).
3. After equalizing the voltage (the difference is no more 0.1V) connect the BMS back.

⚠️ Attention: If, when checking with a multimeter, the bank shows 0V, but its body is swollen - this is a sign of an internal short circuit. Such a jar cannot be charged or disassembled further! Dispose of it in accordance with local regulations.

How to check the BMS board?

To diagnose the controller, connect the battery to the laptop (without the top cover) and check:

1. Does the BMS board heat up when charging is connected?

2. Is there voltage at the output contacts (must match the total voltage of the banks).

3. Does the controller respond to connecting/disconnecting charging (the relay should click).

If the board shows no signs of life, it will have to be replaced or flashed (for this you need a programmer and datasheet for the chip).

Step 4: Replacing faulty cans

If the diagnostics reveal faulty banks, they need to be replaced. To do this:

1. Purchase new cans of the same model (eg. Samsung INR18650-35E or Panasonic NCR21700B).
2. Solder the old cans using a soldering iron of at least 60W and aluminum flux (cans are often held together with aluminum strips).
3. Clean the contacts of the new cans with sandpaper (for better solder).
4. Solder the new cans, observing the polarity (plus to plus, minus to minus).
5. Check with a multimeter that there is no short circuit between the banks.

Important details:

• 🔥 Do not solder cans connected to the BMS - this may burn the controller.
• 🧲 Use a magnet to hold the cans when soldering.
• 🌡️ Do not overheat jars - temperatures above 80°C shorten their service life.
• 🔧 After replacing cans, be sure to balancing (voltage equalization).

To solder aluminum contacts, use a special flux (for example, FSW-33) and low temperature solder. If you have little soldering experience, it is better to use spot welding - it is more reliable and safer.

Step 5: Battery Assembly and Testing

After replacing the cans and checking the BMS board, you can begin assembly:

1. Place the cans in the body, securing them with hot glue or original fasteners.
2. Connect the BMS board, observing the polarity and connection order (see photo taken before disassembly).
3. Close the case using hot glue or double-sided tape (for plastic cases).
4. If the case is metal, solder the seams with a soldering iron.

Before installing the battery in your laptop, perform the following tests:

• 🔌 Connect the battery to the laptop without top cover.
• 📊 Check if it is detected in the BIOS (in some models Lenovo And HP you need to reset the EC controller).
• 🔋 Start charging and monitor the temperature of the cans (should not exceed 45°C).
• 📉 Use the program HWiNFO or BatteryBar to monitor capacity and discharge rate.

If the battery is not detected or discharges quickly, possible reasons:

• 🔌 Incorrect connection of the BMS board.
• 📱 Damage to the controller during soldering.
• 🔋 Unbalancing the cans (each can needs to be recharged separately).

⚠️ Attention: In laptops Apple (starting from 2018) uses a proprietary controller that can block a non-original battery. In this case, you will need to flash the chip using a programmer CH341A and a dump of the original microcircuit.

Common mistakes and how to avoid them

Even experienced technicians sometimes make mistakes when disassembling batteries. Here are the most common ones and ways to prevent them:

Error	Consequences	How to avoid
Soldering cans without turning off the BMS	Controller failure	Always disconnect BMS before soldering
Using acid flux	Contact corrosion	Use only neutral flux (e.g. RMA-223)
Overheating of cans during soldering	Reduced service life	Solder quickly using a heat sink
Wrong polarity when connecting BMS	Short circuit	Check the connection diagram with a multimeter
Ignoring balancing	Rapid failure of new cans	Always equalize voltage before assembly

Another typical problem is false protection alarm (the battery turns off at 20–30% charge). This occurs due to incorrect data in EEPROM controller. Solution:

• 📱 Connect the programmer to the BMS chip (usually BQ20Z45, BQ40Z50 or similar).
• 📊 Read the memory dump and compare it with the reference one (can be found on forums, for example, BadCaps).
• 🔧 Correct the capacity and number of cycles values (use Battery EEPROM Works).

If you are not confident in your soldering skills or working with programmers, it is better to contact a specialist. Errors at this stage can lead to battery fire during the first charge.

FAQ: Answers to frequently asked questions

Is it possible to disassemble the battery if it is swollen?

No, it is strictly forbidden to disassemble a swollen battery. The risk of explosion or fire in this case is extremely high. Such a battery must be disposed of at special collection points (for example, electronics stores or service centers). If the laptop is still working, immediately unplug it and remove the battery (if possible without disassembling).

What kind of soldering iron is needed to replace cans?

The best option is a soldering iron with a power of 60–80W with temperature control (for example, Hakko FX-888D or KSGER T12). To solder aluminum contacts, you will need a special tip and flux (for example, FSW-33). An alternative to soldering is spot welding (more reliable, but requires special equipment).

What should I do if the battery does not charge after replacing the cans?

There may be several reasons:

1. Incorrect connection of the BMS board (check the polarity and integrity of the contacts).
2. Unbalancing the cans (charge each one separately to the same voltage).
3. The controller protection has tripped (reset via programmer is required).
4. The thermistor is damaged (check the resistance with a multimeter - it should be ~10 kOhm).

Start by checking the voltage at the output of the BMS board. If it is not there, the problem is in the controller.

How long will the battery last after replacing the batteries?

The service life depends on the quality of the new cans and operating conditions:

• 🔋 Original cans (For example, Panasonic or Samsung) - 3–5 years with proper balancing.
• 🔋 Budget banks (For example, UltraFire) - 1–2 years (higher risk of bloating).

To extend battery life:

• 📉 Do not discharge below 20%.
• 🔌 Do not leave the laptop on charge all the time (optimally - 40–80%).
• 🌡️ Avoid overheating (use a cooling pad).

Can the battery be used without the BMS board?

No, this is extremely dangerous. The BMS board performs several critical functions:

• 🛡️ Short circuit protection.
• 📊 Voltage balancing between banks.
• 🌡️ Temperature control.
• 🔌 Limitation of charge/discharge current.

Without a BMS, the risk of battery overheating, swelling, or even fire increases tenfold. If the controller is broken, it must be repaired or replaced with a similar one.