Computer Repair · October 29, 2026 · ComputerKing Team

Laptop Base Bulging, Trackpad Lifting — Is It Always a Swollen Battery? How to Tell Without Opening the Machine, and What to Prepare Before Repair

A bulging base or lifting trackpad does not necessarily mean a swollen battery. Use five checks that need no opening to narrow the possibilities, treat it as swelling if you cannot tell, and prepare five exterior photo sets and six items of machine information before repair.

Key Points

• A bulging base, a lifting trackpad, or a laptop that no longer sits flat does not necessarily mean a swollen battery. A loose hinge, an ageing trackpad mechanism, a warped bottom cover, or a foreign object inside can produce a similar appearance.
• Without opening the machine, five exterior checks can narrow the possibilities: the flat-table test, the lid-closing test, trackpad feel, seam inspection, and keyboard feel.
• If you cannot tell, treat it as a swollen battery: stop using it immediately, shut it down, and unplug the charger. Do not charge it again, and do not press on the bulge to test it.
• Before repair, take five sets of exterior photos and note six items of machine information, so the technician can judge accurately at first sight instead of relying on a verbal description.
• Whether to replace the battery or retire the machine, and what it costs, all depend on the inspection result and are quoted individually. This article gives no fixed price.

Introduction

A laptop that used to sit flat on a desk suddenly rocks on one side. The trackpad feels as if something is pushing it up from underneath. A gap appears between the bottom cover and the body for no obvious reason. Many people's first reaction is: "Is the battery swelling?" And the second reaction is often to look up a teardown guide and try to open the cover to check.

This article covers the step before opening anything: how to tell "looks like swelling" from "actually swelling" without opening the machine at all, and how to prepare an evidence pack for repair. This step deserves its own article because it decides two things: first, whether you might keep using a machine whose battery is in fact swelling because you guessed wrong; and second, whether the technician receiving the machine can check the right thing straight away, or has to start again from a vague verbal description.

This article does not repeat the full emergency procedure, nor does it cover the replace-or-retire decision. Both already have dedicated articles on this site (see the Sources section). This article covers only three things: how to check without opening the machine, how to distinguish other causes, and how to record everything before repair.

First Principle: If You Cannot Tell, Treat It as Swelling

Before starting any check, set one safety line: if you finish checking and still cannot tell, treat the machine as if the battery is swelling. Stop using it immediately, shut it down, unplug the charger, and then arrange repair. The reason is simple: the cost of a swollen battery is a safety risk, while the cost of the other causes (for example a loose hinge or a slightly warped cover) is mostly inconvenience in use. Treating an unknown case as the more serious one is the only approach that does not increase the risk.

That line does not mean "every bulge is definitely swelling". When you hand the machine in, stating clearly which signs you observed and which did not appear lets the technician judge accurately, instead of treating every bulging machine as the same fault for quoting purposes.

One more point to state clearly: all checks below are exterior checks. They do not require, and should not involve, opening the bottom cover. Built-in batteries are held in place with strong adhesive, and prying them out carries its own risk. The purpose of checking is to narrow the possibilities and prepare repair information, not to let you diagnose the fault at home.

Five Checks Without Opening the Machine

Before checking, shut the machine down completely, unplug the charger, and place it on a hard, flat, dry, non-flammable surface. Use a light touch throughout. Do not press hard on the bulging area — pressing to test is itself an action to avoid. Do each of the five checks in turn, and note down each result.

Check 1: The Flat-Table Test

Close the lid, place the machine bottom-down on a table you know is flat (for example a glass or stone surface), and gently press each corner in turn with a finger to see whether the machine rocks.

• If all four corners sit firmly on the table and the machine does not rock at all, bottom-cover bulging is less likely, and the problem may be elsewhere.
• If one side or one corner clearly lifts, and the machine rocks when placed down, that is a signal worth recording: the shape of the bottom cover has already changed.
• Note which corner lifts, and roughly by how much (an everyday comparison such as "about the thickness of a fingernail" is enough; no precise measurement is needed).

One caveat: a table that is not itself flat will make the test unreliable. Repeat the same test on a second flat table, and only count a result that appears both times.

Check 2: The Lid-Closing Test

Slowly close the lid and see whether the left and right sides close symmetrically.

• If one side closes and the other does not, or one side shows a clearly wider gap after closing, note which side.
• If you feel resistance while closing, do not force it. Stop, and simply note "resistance when closing".
• A hinge problem usually makes lid closing asymmetrical, but a swelling battery can also push the body out of shape so the lid no longer closes evenly. This check alone can therefore only tell you "the shape is asymmetrical", not confirm a diagnosis.

Check 3: Trackpad Feel

The trackpad is the location that most often makes people suspect swelling, because a swelling battery often pushes the trackpad up from underneath.

• Gently press the left and right sides of the trackpad, and feel whether both sides feel the same, or whether one side feels unusually stiff, will not press down, or does not spring back after pressing.
• At the same time, check whether the trackpad surface sits level with the palm rest, or whether one side is slightly raised.
• A change in feel has many causes: an ageing trackpad mechanism, a foreign object inside, or a battery swelling underneath are all possible. The value of this check is that it lets you say "which side, and how it differs" — not that it settles the diagnosis.

Check 4: Seam Inspection

In good light, slowly look along all four sides of the machine at the seam between the bottom cover and the body.

• Check whether the seam width is consistent all the way around, or whether one section suddenly widens.
• Check around the bottom-cover screw positions for signs of being pushed up, and whether the edge of the bottom cover is slightly bent.
• Check whether the body shows cracks or impact marks — if the machine has been dropped before, that is relevant to the cause of the deformation, and this information matters at repair. Do not hide it.
• Observation is enough. Do not try to press the bottom cover back into place, and do not pry the seam open with a tool to look inside.

Check 5: Keyboard Feel

Place the machine flat and gently press each key in turn, watching for any individual key that sits unusually high, sticks when pressed, or feels clearly different from its neighbours.

• A swelling battery can sometimes push the keyboard up from below, making individual keys sit high; but dust or a foreign object under a key can produce a similar feel.
• Note which keys show anything unusual. Press gently once each — do not press hard repeatedly to "test it properly".

After all five checks, you should hold a simple record: whether the machine rocks on a flat table, which corner lifts, which side closes unevenly, which side of the trackpad feels different, which section of seam has widened, and which keys feel abnormal. That record is the input for the comparison table in the next section, and the core of the repair evidence pack.

Comparison Table: Five Situations That Look Like Swelling

The table below lists five common situations that change the exterior shape, with their more typical appearances. Note the wording: "more typical" does not mean "always". One machine can have two causes at once. This table only narrows the direction; it is not a diagnostic tool.

How to use this table: match your five check results against it, item by item.

• If several checks react at the same time, and the change appeared gradually, swelling is the more likely direction, and you should stop using the machine and arrange repair without further delay.
• If only one check reacts and all the others are normal, swelling is relatively less likely — but it still cannot be ruled out. Early swelling, for example, may affect only trackpad feel. In this case, arrange an inspection promptly rather than continuing to use the machine as normal.
• If all five checks are normal but something still looks wrong to you, note down the location that looks wrong and mention it at repair, leaving the decision to the inspection.

The safety line stands again: this table narrows the direction; it is not a diagnosis. In any case where you cannot tell, treat it as swelling.

The Repair Evidence Pack: Five Photo Sets and Six Items of Information

Many repair conversations go wrong not because the technician cannot find the fault, but because the owner's verbal description is too vague — "the machine is a bit bulgy" or "the trackpad feels weird" gives the technician nothing to prepare for before first seeing the machine. The evidence pack below exists so the first conversation is already specific enough.

Five Exterior Photo Sets (Exterior Only, No Opening)

1. Whole machine, front view: the machine with its lid closed, sitting on a flat table, showing the whole machine and how it contacts the table surface.

2. Close-up of the lifted area: the bulging bottom cover or the widened seam section, photographed from the side so the extent of the bulge is visible.

3. Trackpad area: the trackpad and palm rest, showing whether the trackpad sits level or one side is raised.

4. Lid-closing condition: after closing the lid, the left and right seam widths side by side for comparison.

5. Bottom label: the brand, model, and serial number label on the bottom of the machine (cover any other personal information first, leaving only brand, model, and serial number).

When photographing, do not press the machine hard to get a clearer shot, and do not turn the machine over or prop it up with objects. Photograph it as it naturally sits on the table.

Six Items of Machine Information

With these five photo sets and six items ready to hand over together, the technician does not need to call back to ask each question one by one, and you do not need to recall each detail from memory. On cost, to be clear: inspection, battery replacement, and any related parts replacement all depend on brand, model, and inspection result, and must be quoted individually. This article gives no fixed price.

While Waiting for Repair: What to Do, and What Not to Do

Between noticing the shape change and actually handing the machine to a technician, there may be a gap of several hours or even a day or two. What you do during that wait is worth stating clearly:

One common mistake during the wait deserves a special mention: pressing the trackpad a few more times "to check whether it really is being pushed up". That action is itself a press test, which should be avoided when swelling is suspected. Do each check once, note the result, and stop. Do not test repeatedly.

Common Misunderstandings

Misunderstanding 1: "The system says battery health is normal, so it cannot be swelling."

A system battery-health figure reflects capacity and cycle condition, not shape. A machine whose shape has already changed can still show a normal figure. Shape signals take priority over software figures; do not use a normal figure to dismiss a visible change.

Misunderstanding 2: "Only the trackpad will not press down, so it must just be a trackpad fault."

A change in trackpad feel has many causes, and a battery swelling underneath the trackpad is one of them. Precisely because swelling can present as a trackpad problem, judging "trackpad fault" from that one symptom alone and continuing to use the machine carries risk. The correct approach is to complete all five checks, narrow the direction with the comparison table, and leave the decision to inspection.

Misunderstanding 3: "Photographing and recording is too much trouble; describing it verbally is enough."

Verbal descriptions distort easily: "a bit bulgy" can mean a slight bend or a clear lift, and the handling order for the two is completely different. Five photo sets and six items take less than half an hour to prepare in total, but they make the first conversation specific enough and reduce back-and-forth questions.

Misunderstanding 4: "Before repair, I should open it up myself to describe it clearly."

The opposite is true. Opening the bottom cover yourself, quite apart from the safety risk, changes the shape, seams, and screw condition, making it harder for the technician to judge the original condition. Exterior checks plus photo records are already enough for the technician to judge; you do not need to open the machine to prove anything.

Summary

When swelling is suspected, there is no need to rush to a conclusion, and no need to rush to open the machine. First follow the safety line: if you cannot tell, treat it as swelling — stop using it, shut it down, unplug it. Then use the five checks that need no opening to narrow the possibilities: flat-table test, lid-closing test, trackpad feel, seam inspection, keyboard feel. Then compare against the five situations in the table to see which fits best. Finally, prepare five exterior photo sets and six items of machine information, and hand them over together to the technician. Do each check once; during the wait, do not test by repeated pressing, do not charge, and do not switch the machine on to copy files. Remember, the purpose of this article is not to let you diagnose the fault at home, but to take you from "something looks wrong" to "a machine with complete information handed to a professional" by the safest and most specific route.

Q: The laptop rocks on a table. Does that mean the battery is swelling?

A: Not necessarily. A reaction in the flat-table test only shows that the shape of the bottom cover has already changed. The cause could be a swelling battery, a warped cover, impact deformation, or several other possibilities. Check the other four items as well, narrow the direction using the comparison table in this article, and if you cannot tell, treat it as swelling: stop using it, shut it down, unplug it, and arrange repair promptly.

Q: One side of the trackpad feels stiff and the other side feels normal. What does that mean?

A: It means trackpad feel has become asymmetrical. The cause could be a battery swelling underneath pushing the trackpad up, an ageing trackpad mechanism, or a foreign object inside. This one item alone cannot confirm a diagnosis. Complete all five checks, see whether other areas have changed at the same time, and leave the decision to the technician's inspection.

Q: The system says battery health is normal. Can swelling be ruled out?

A: No. A system battery-health figure reflects capacity and cycle condition, not shape. A shape that has already changed with a still-normal figure is entirely possible. Shape signals take priority over software figures, and once a shape change appears, it should be handled using the checks and the safety line in this article.

Q: Do the five checks require opening the bottom cover?

A: No, all five are exterior checks, and they should not involve opening the cover. Built-in batteries are held in place with strong adhesive, and prying them out yourself carries risk. Opening the cover also changes the shape and seam condition, making it harder for the technician to judge. Exterior checks plus photo records are enough.

Q: When photographing, can I turn the machine over or press it down to get a clearer shot?

A: No. Photograph the machine as it naturally sits on the table. Do not press hard on the bulging area, and do not prop the machine up with objects. Pressing to test is itself an action to avoid, and pressing for the sake of a photo puts the purpose backwards.

Q: At repair, why should I mention whether the machine has been dropped or exposed to liquid?

A: Because drops and liquid exposure are both possible causes of body deformation. When the technician knows this background, the source of the shape change can be judged more accurately, instead of treating every bulge as the same fault. Hiding background information only makes the judgement less accurate, and the quotation may also be less accurate.

Q: While waiting for repair over a few days, how should the machine be stored?

A: Shut down, charger unplugged, placed on a hard, flat, dry, ventilated, non-flammable surface, in a location household members and pets will not easily touch. Do not pack it into a backpack or drawer, do not place heavy objects on it, do not charge it, and do not switch it on again to copy files.

Q: How does this article differ from the earlier battery-swelling safety guide and the replace-or-retire article?

A: The safety guide covers the emergency steps immediately after swelling is found. The replace-or-retire article covers the decision after emergency handling. This article covers the step before both: when swelling is suspected but not yet confirmed, how to check without opening the machine, how to distinguish other causes, and how to prepare a repair evidence pack. The order of the three articles is: this article's checking and recording, then the safety guide's emergency handling, then the replace-or-retire decision.

Sources

• ComputerKing internal article, Laptop Battery Swelling Safety Guide (emergency steps after swelling is found, irreversible damage, official recycling channels): https://www.computerking.hk/blog/laptop-battery-swelling-safety-guide/
• ComputerKing internal article, What to Do After a Laptop Battery Swells: Replace the Battery or Retire the Machine? Protect Your Data First, Then Decide on Three Factors (decision after emergency handling, inspection items when replacing a battery): https://www.computerking.hk/blog/laptop-swollen-battery-replace-or-retire/
• ComputerKing internal article, MacBook Battery Health Guide (cycle count, when to replace, original vs third-party batteries): https://www.computerking.hk/blog/macbook-battery-health-guide/
• Apple Support, If you see battery 'Service Recommended' on your Mac laptop: built-in batteries should only be replaced through authorised repair channels; MacBook batteries are designed to retain up to 80% of original capacity at 1,000 complete charge cycles. https://support.apple.com/en-ca/108376
• Waste Reduction Website, Rechargeable Battery Recycling Programme FAQ: damaged rechargeable batteries are not suitable for collection boxes; suspected damaged rechargeable batteries should have their metal terminals covered with non-conductive tape and be sealed in a plastic bag before handling. https://www.wastereduction.gov.hk/en-hk/recycling-faq/rechargeable-battery-recycling-programme-faq