Battery Repair · October 20, 2026 · ComputerKing Team

Laptop Battery Swelling Safety Guide: Signs, Stop, Recycle

A swollen battery is irreversible damage: stop using it, power off and unplug immediately; never puncture, pry or press it — hand it to the manufacturer or an official recycler.

# Laptop Battery Swelling Safety Guide: Spot the Signs, Stop Using It, Recycle It Properly

Key Summary

A swollen battery is irreversible damage: stop using it, power off and unplug immediately; never puncture, pry or press it — hand it to the manufacturer or an official recycler, and never throw it in the bin.

*This guide compiles official guidance from Apple, Dell, Lenovo and HP, public information from Hong Kong's Environmental Protection Department, and public reports from 2025–2026. Every fact carries a source; the full source list is at the end. Prices only show figures with a public source — where none exists it says "quote on request". No estimates, no guessing.*

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1. What is battery swelling, and why does it happen?

Battery swelling is not just "a bit of warping from old age". According to battery engineering resource AEANET, swelling is caused by electrolyte decomposition producing gas (outgassing): overcharging, overheating, over-discharging, ageing or manufacturing defects all accelerate electrolyte breakdown, generating hydrogen, carbon dioxide, carbon monoxide, hydrocarbons and other gases. These gases get trapped inside the sealed cell, internal pressure rises, and the battery swells.

Other chemical mechanisms include SEI (solid electrolyte interphase) film breakdown, lithium plating reacting with the electrolyte, and separator damage causing internal short circuits. The critical point: swelling is irreversible internal structural damage — it cannot be repaired; the only safe option is replacing the whole battery. Lithium-ion and lithium-polymer batteries swell most often; nickel-cadmium and nickel-metal hydride are rarer but not immune.

Dell's official knowledge base article (KB 000128491) also explains that modern Dell laptops use lithium-ion polymer batteries built with flexible multilayer pouches, which can sometimes expand. Causes include normal battery ageing, usage habits and environmental factors (heat or humidity). Dell stresses this is a known characteristic of this battery technology, an industry standard — not something unique to Dell.

HP technical document c05159228 (cited via the HP official community) states that polymer battery cells can swell due to damage, improper maintenance or the manufacturing process; prolonged low voltage, high temperature and cell imbalance can also cause it.

Recent public reports for context:

• US Federal Aviation Administration (FAA) data shows 93 verified lithium-battery aviation incidents (smoke, fire or extreme heat) in 2025, up from 89 in 2024. The FAA notes lithium batteries can enter "thermal runaway", triggered by physical damage, overheating, overcharging, improper packaging, water exposure and manufacturing defects. (Note: these are aviation statistics, not laptop-swelling figures.)
• In December 2025, the US CPSC and INIU announced a recall of about 210,000 INIU power banks (model BI B41) following a series of overheating incidents including multiple fires and minor burns.
• The Casely mobile phone charger (model E33A) was first recalled in April 2025 (about 429,200 units), then re-announced in April 2026, disclosing that a 75-year-old New Jersey woman suffered second-to-third-degree burns in a fire/explosion while using the charger in August 2024 and later died from complications. This must be stated clearly: it was a phone charger case, not a laptop battery — but it belongs to the same lithium-battery safety context.
• In Hong Kong, ezone.hk reported on 10 October 2026 that a local netizen left spare batteries at home, went travelling, and came back to find a battery severely swollen — fortunately it did not catch fire. The report describes improperly handled waste lithium batteries as a household "ticking time bomb".
• In December 2025, a user shared on the iFixit community that their MacBook Air 13" (2019) first suffered plunging battery life then shut down; opening it up revealed the original battery was already slightly swollen. (This is a user-reported case, cited for symptom reference only; this guide does not recommend opening up your machine to replace a swollen battery yourself.)

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2. How to recognise a swollen battery: the symptom checklist

Dell's official knowledge base (KB 000128491) lists these warning signs:

1. Bulging or swelling in the battery compartment area

2. Gaps or separation in the chassis seams

3. The trackpad or keyboard feels wrong when pressed — as if pushed up from underneath

4. The laptop wobbles when placed on a flat table

5. The screen won't close, or doesn't align when closed

Third-party repair and information sites add detail: US repair chain Micro Center notes the trackpad, keyboard and base are the most common swelling locations; symptoms include rocking back and forth on a flat table (not just a missing rubber foot), some keys failing (even after cleaning the keyboard), an unresponsive or hard-to-click trackpad, a visible gap between keyboard and screen when the lid is closed, and chassis trim pieces popping out. Electropapa (updated October 2026) adds: poor or dead trackpad response, a bulging or deformed base, chassis warping that makes some keys hard to use, abnormal heat; a chemical smell, hissing sounds or poor contact while charging are warning signs — if spotted, power off immediately, disconnect power and stop using the machine.

iFixit's swollen-battery guide mentions an easily missed signal: a sweet, metallic chemical smell, which can indicate battery gas leaking. BatterySkills says most laptop batteries start showing wear after about 2–4 years; swollen batteries are often accompanied by sharply reduced battery life, random shutdowns and abnormal heat.

A crucial reminder: an HP official community staff member stated explicitly that even if HP Support Assistant reports the battery as "operating normally", a visibly swollen battery is already a clear sign it is unsafe. Don't assume all is well just because the software says so.

If you use a MacBook, this 3-warning-signs quick check can help you judge quickly whether it really is battery swelling.

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3. You found swelling — what to do right now

Combining official guidance from Apple, Dell, Lenovo and HP with Engadget's September 2026 feature, in this order:

1. Stop using it immediately, power off, and unplug the charger. All four manufacturers and the media guidance agree.

2. Do not press, squeeze, bend or puncture the battery; do not try to pry out a battery that is stuck because of swelling. Dell's official service manual states that puncturing, bending or squeezing is dangerous.

3. Move the device to a hard, flat, non-flammable surface, or isolate it in a non-metal container (e.g. glass or ceramic, which prevents short circuits), away from flammables and heat, in a dry, ventilated spot.

4. Dell's official manual "discharge" step (stated in full): Dell requires the battery to be discharged before handling — unplug the AC adapter and run the machine on battery power alone until it can no longer power on; after discharging, that battery must not be used again, and you should contact Dell technical support to arrange a replacement. Be clear: this is not telling you to "keep using it for now". "Stop using" means no longer using the machine as a normal computer; "discharge" is a preparation step before disassembly/handling. If you plan to carry out Dell's discharge step, set the device down in its safe spot first (step 3 above) and only then power it on to run it down.

If you're unsure, the safest route is: power off, unplug, isolate, and go straight to professional repair — no need to do it yourself.

5. The emergency line — if any of these occur: smoke, hissing, popping sounds, a strong chemical smell, leaking fluid, abnormal heat. Don't touch or move it, evacuate people and pets, and call 999 (Hong Kong emergency number).

6. Contact the manufacturer's support or an authorised service centre to arrange a replacement. Within warranty, this is usually free.

Before sending it for repair or disposal: keep it powered off and unplugged, store it somewhere dry, ventilated, cool, and away from flammables and metal objects; don't store it for a long time — hand it to a qualified recycler as soon as possible.

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4. Official manufacturer guidance, side by side

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5. Where the manufacturers' statements disagree — we'll lay it out honestly

While researching, we found several points where the manufacturers — even within the same company — say different things. Rather than pretending otherwise, here they are:

1. Contradictory HP community statements. In the same HP official community, staff member Hawks_Eye wrote in one reply that a swollen battery does "not present a safety issue"; another staff member, Max3Aj, wrote in a different reply that a swollen battery "is a safety issue and should be handled as soon as possible". Both are HP employee responses, saying different things. Our position: take the conservative side — treat it as a safety risk and handle it promptly, don't wait.

2. Apple's 2018 statement. In 2018 Apple launched a battery replacement programme for the 13-inch MacBook Pro (without Touch Bar), covering units manufactured October 2016 to October 2017. Apple acknowledged a component could cause battery swelling and offered free replacements (refunds for those who had already paid), while at the same time calling the defect "not a safety issue". We quote this as stated, without drawing conclusions — readers can judge for themselves; either way, a swollen battery should be stopped and replaced.

3. Dell's "discharge" vs "stop using". Dell's manual both demands you stop using the machine and requires unplugging the adapter and running on battery until it can no longer power on, to discharge the battery first. The full context: "stop using" = no longer using the machine as a normal computer; "discharge" = a preparation step before disassembly/handling — and Dell requires that the battery not be used again afterwards. Never simplify this into "you can keep using it for now".

4. Is improper disposal "illegal"? One report wrote that dumping waste batteries "may violate relevant regulations", but we could not find a Hong Kong statute expressly supporting that claim, so we will not assert illegality. The accurate statement: never throw them in household rubbish bins or general recycling bins — they must go through official recycling channels (next section), per consistent guidance from the EPD and the US CPSC.

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6. Disposal and recycling in Hong Kong: the correct channels

Rechargeable Battery Recycling Programme (Environmental Protection Department)

Covers all reusable rechargeable batteries, including lithium-ion batteries (stated to include laptop/tablet batteries). Before recycling you must:

1. Remove the battery from the device;

2. Tape over the battery electrodes (positive and negative terminals) with adhesive tape to prevent short circuits;

3. Damaged batteries must not go into collection boxes — easily damaged batteries must be sealed in a plastic bag and taped shut before handover;

4. Take them to a collection point (including the "GREEN@COMMUNITY" network).

Collected batteries are sorted by type, given preliminary treatment, stored, then exported for recycling.

WEEE Producer Responsibility Scheme ("Four Electricals and One Computer")

The scheme covers air conditioners, refrigerators, washing machines, televisions, computers, printers, scanners and monitors, effective 1 August 2018. Even without buying a new machine, the public can book free door-to-door collection: hotline 2676 8888 or WhatsApp 6081 5096 (government operator). EPD enquiry hotline 2310 0223, website weee.gov.hk. GREEN@COMMUNITY recycling points also accept waste electrical appliances.

In other words: a whole old laptop containing a swollen battery can go through WEEE free door-to-door collection; a battery removed on its own goes through the Rechargeable Battery Recycling Programme, sealed as a damaged battery.

Emergency storage points (compiled by ezone.hk, 10 Oct 2026)

Never squeeze or puncture; handle gently, remove it with as little force as possible or move the whole device somewhere safe; isolate it in a non-metal container (e.g. glass or ceramic, which prevents short circuits), away from flammables, in a dry, ventilated place away from heat; don't store it long-term — hand it to a qualified recycler promptly; tape the electrodes before recycling; waste batteries must not be thrown away as general household rubbish.

The US CPSC, in the INIU recall notice, likewise stresses lithium batteries must not go into general household rubbish or recycling bins — they must go to designated hazardous-waste facilities per local rules.

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7. What does a battery replacement cost? Only figures with public sources

Two declarations: first, the independent repair-shop prices above are for reference only — not manufacturer prices; actual charges follow each shop's latest price list. Second, we found no public price list for official Dell, Lenovo or HP battery replacement in Hong Kong within the research scope — these are all "quote on request", and we won't estimate.

Deciding between a battery replacement and a new machine? This guide walks through the choice.

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8. Common myths, debunked

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9. Prevention: slowing battery ageing

Apple's official advice: turn on Optimised Battery Charging — macOS learns your daily charging routine and holds the charge at 80% when it expects you won't unplug soon, only topping up before you use it, reducing time spent at full-charge high voltage; newer macOS lets you manually set a charge limit between 80%–100%; the ideal operating environment is about 16°C–22°C — avoid exposure above 35°C (e.g. direct sun, a baking car interior), as heat permanently shortens battery life; for long-term storage (unused for over six months) charge to about 50%, power off, store somewhere cool and dry (below 32°C), and top back up to 50% every six months.

Lenovo: Lenovo Vantage offers Battery Charge Threshold (ThinkPads can set start/stop charge percentages, e.g. start at 75%, stop at 80%) and Conservation Mode (IdeaPad/Yoga/Legion lock the charge ceiling at about 55–60%); the official safety guide says built-in batteries in storage should be kept at about 30%–50% charge at room temperature, charging once a year to prevent over-discharge; it also warns that using the wrong battery model risks explosion — only use Lenovo-recommended models.

HP: the official community recommends avoiding long periods at 100% charge combined with heat (especially gaming laptops), and enabling the BIOS Adaptive Battery Optimizer.

General practices (consistent across sources): don't leave the laptop plugged in at 100% indefinitely, especially when used as a desktop; the 20%–80% range is ideal for daily use; avoid frequently running it down to 0% before charging; don't use it for long periods on soft surfaces like beds or sofas (they block the vents); ensure ventilation under heavy loads (video editing/gaming); never leave the laptop in a baking car or direct sun for long; use original/certified chargers. Engadget adds: for long-term storage keep about 50% charge and power it on to check roughly every three months.

How to check battery health, by the way: on Windows, open an elevated Command Prompt and run `powercfg /batteryreport` — it generates an HTML report; divide Full Charge Capacity by Design Capacity for the health percentage. On macOS, hold Option, click the Apple menu → System Information → Power to see the cycle count; most MacBook models from 2010 onwards are rated for 1,000 cycles, and Apple designs the battery to retain up to 80% of original capacity at the rated cycle count. One cycle = cumulative use equal to 100% of battery capacity (not one plug-in = one cycle). Lenovo users can check cycle count and full-charge capacity in Lenovo Vantage.

Note for older machines: ezone.hk reported in October 2026 that the 2017 12-inch MacBook is now on Apple's vintage list, with general hardware service discontinued; but Mac laptops remain eligible for a "battery-only service" extension for up to 10 years from the last date of sale, while parts remain in stock (battery only — screen/keyboard/logic board not included).

Hong Kong's humid weather makes heat worse for batteries: cooling tips for humid weather.

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10. FAQ

Q1: The battery is only slightly swollen — can I keep using it for now?

No. Swelling means the internal structure is already irreversibly damaged and can worsen, leak or catch fire at any time. Apple, Dell, Lenovo and HP all say the same: stop using it immediately and arrange a replacement. AEANET states no degree of swelling is safe.

Q2: Can I puncture it to release the gas, or pry the battery out myself?

Absolutely not — this is the most dangerous idea. Puncturing releases flammable electrolyte and can create sparks, causing immediate fire or even explosion. Dell's official service manual, Lenovo's official safety guide and HP's official notices all prohibit squeezing, puncturing, bending or prying batteries. Leave it to the manufacturer or an authorised servicer.

Q3: Can I keep using it plugged into the charger?

No. Charging adds heat and energy to an already-faulty cell. The correct action is to stop using the machine, power off and unplug the charger.

Q4: How should I dispose of a swollen battery or a whole old laptop?

A removed swollen battery: tape over the positive and negative electrodes; seal damaged batteries in a plastic bag taped shut; take it to a Rechargeable Battery Recycling Programme collection point (including GREEN@COMMUNITY) — never into an ordinary collection box. A whole old laptop: book WEEE free door-to-door collection (2676 8888 / WhatsApp 6081 5096) or take it to a GREEN@COMMUNITY point. Never throw them in household rubbish bins or general recycling bins.

Q5: How much does a battery replacement cost?

Figures with public sources: Apple US official replacement about US$149–$249 (US pricing, not Hong Kong); AppleCare+ (Hong Kong) replaces the battery free when health drops below 80%; independent third party ILIFE-HK's public price list shows MacBook Air replacement HK$500–950 and Pro HK$600–950 (not manufacturer pricing, for reference only). No public HKD price list exists for Apple Hong Kong out-of-warranty Mac battery service, nor for official Dell, Lenovo or HP replacement in Hong Kong — these are all quote on request, and we won't estimate.

Q6: My Mac is very old — will Apple still replace its battery?

The 2017 12-inch MacBook is on Apple's vintage list and general hardware service has ended. However, Mac laptops remain eligible for a "battery-only service" extension for up to 10 years from the last date of sale, while parts remain in stock (battery only). Check with Apple or an authorised service provider.

Q7: I smell something chemical at night / see the machine smoking — what do I do?

Don't touch or move the machine, evacuate family members and pets, and call 999 immediately. Don't try to put out the fire or handle the battery yourself before firefighters arrive.

Q8: How do I know if my battery is still healthy?

On Windows, `powercfg /batteryreport` shows design capacity vs current full-charge capacity; on macOS, System Information shows the cycle count (1,000-cycle rating for 2010+ models) and the battery health status ("Normal" / "Service Recommended"); Lenovo users can check in Lenovo Vantage. But remember: software saying "normal" doesn't mean all is well — visible swelling is already an unsafe signal.

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Sources

1. FAA 2025: 93 verified lithium-battery aviation incidents (up from 89 in 2024); thermal runaway triggers — https://airguide.info/american-airlines-laptop-fire-highlights-battery-safety-risk/

2. INIU power bank recall 8 Dec 2025, about 210,000 units; CPSC: never into household rubbish — https://www.prismnews.com/news/about-210000-iniu-power-banks-recalled-after-fires

3. INIU recall supplement: CPSC advises contacting local hazardous-waste programmes — https://www.newstarget.com/2025-12-09-portable-power-banks-amazon-recalled.html

4. Casely phone-charger recall (first recall Apr 2025, ~429,200 units; re-announced Apr 2026 disclosing a 75-year-old woman's death) — a phone charger, not a laptop — https://lawstreetmedia.com/insights/fire-in-the-cabin-questions-in-the-files/

5. Hong Kong netizen's battery severely swollen after travel; swollen-battery emergency steps (ezone.hk, 10 Oct 2026) — https://ezone.hk/article/20079576/閒置電池膨脹變-計時炸彈-即學-招廢棄電池處理方法

6. MacBook Air 2019 swollen-battery user case (iFixit, 4 Dec 2025) — https://jp.ifixit.com/Answers/History/929206

7. Engadget 13 Sep 2026: trackpad popping out = stop immediately; Apple US replacement US$149–249; store at 50% — https://www.engadget.com/2252834/laptop-trackpad-popping-out-stop-using-immediately-battery-swelling/

8. Apple: only trained technicians should replace batteries; stop use if damage suspected (quoting Apple Support's original text) — http://cellfixhouston.com/blog/iphone-screen-lifting/

9. Apple 2018 13-inch MacBook Pro battery replacement programme (units made Oct 2016–Oct 2017; Apple said not a safety issue) — https://www.aivanet.com/2018/04/apple-offers-to-replace-swollen-batteries-in-certain-macbook-pros/

10. Dell official service manual: swollen-battery chapter (stop use, discharge, no squeeze/puncture/pry, contact support) — https://www.dell.com/support/manuals/en-us/precision-15-3560-laptop/precision_3560_sm/Handling-swollen-rechargeable-Li-ion-batteries?guid=guid-e3342b2e-3097-42e7-a605-284fd4d652a4&lang=en-us

11. Dell swollen-battery symptom list (cited) — https://theitguysfix.com/2026/08/31/laptop-swollen-battery-safe-response-plan-2026/

12. Dell official KB 000128491: symptoms, causes, six immediate actions — https://www.dell.com/support/kbdoc/en-tt/000128491

13. Lenovo official safety guide: no disassembly/squeeze/puncture/short; built-in batteries via authorised service only — https://download.lenovo.com/consumer/mobiles_pub/new_ml_swg_en_ja_ko.pdf (note: the URL in the research report contained a space and returned 404; replaced with the working link to another language version of the same official Lenovo safety guide)

14. HP official safety notice (Traditional Chinese): no disassembly/crush/puncture; no shorting; not into fire/water — https://www.manualshelf.com/manual/hp/k3c83ear/guidelines-for-the-use-of-regulatory-safety-and-environmental-announcements-chinese/page-21.html

15. HP staff: stop immediately, don't charge or press, hard flat surface away from flammables — https://h30434.www3.hp.com/t5/Notebook-Hardware-and-Upgrade-Questions/Battery-issue/td-p/9433093

16. HP support: swollen battery is a safety issue, handle ASAP; never puncture/disassemble yourself — https://h30434.www3.hp.com/t5/Notebook-Hardware-and-Upgrade-Questions/Swollen-battery-issue/td-p/9413974

17. HP community: Adaptive Battery Optimizer, avoid sustained 100% charging — https://h30434.www3.hp.com/t5/Gaming-Notebooks/HP-Victus-15-fb0xxx-swollen-battery-safe-usage-questions/td-p/9584892

18. Swelling cause: electrolyte decomposition producing gas; irreversible, replace only — https://www.aeanet.org/why-do-batteries-swell/

19. Swelling chemistry (SEI breakdown, lithium plating, internal shorts) — https://walkermetalsmith.com/why-do-lithium-ion-batteries-swell/

20. Swollen batteries irreparable; puncturing extremely dangerous — https://www.aeanet.org/can-a-swollen-iphone-battery-explode/

21. EPD Rechargeable Battery Recycling Programme: tape electrodes, seal damaged batteries, collection points — http://www.wastereduction.gov.hk/en-hk/waste-reduction-programme/rechargeable-battery-recycling-programme

22. WEEE free door-to-door collection 2676 8888 / WhatsApp 6081 5096; EPD 2310 0223 — https://gia.info.gov.hk/general/201807/27/P2018072700440_288924_1_1532681261277.pdf

23. WEEE page: free collection service, GREEN@COMMUNITY accepts waste appliances — http://www.wastereduction.gov.hk/en-hk/waste-reduction-programme/weee-hk

24. AppleCare+ Hong Kong: free replacement below 80% health; accidental damage HK$799 / HK$2,299 — https://www.hkcsl.com/en/macbook-applecare/

25. Apple US replacement reference pricing US$159 / 199 / 249 tiers — https://sdmactech.com/repair-or-replace-batteries-applecare-and-the-real-math-on-aging-macs/

26. ILIFE-HK public price list (HKD, independent third party) — https://www.ilifehk.com/

27. GAAHK 維修快: on-site inspection from HK$200 (independent third party) — https://www.gahk.com.hk/services/macbook-battery-replacement/

28. Apple vintage-model battery-only service extension (ezone.hk, 15 Oct 2026) — https://ezone.hk/article/20114106/apple-%E6%9B%B4%E6%96%B0%E5%81%9C%E7%94%A2%E5%90%8D%E5%96%AE-%E5%90%8B-macbook-%E7%AD%89%E4%B8%89%E6%AC%BE%E8%88%8A%E6%A9%9F%E9%80%80%E5%BD%B9-%E5%AE%87%E6%96%B9%E7%B6%AD%E4%BF%AE%E6%9C%8D%E5%8B%99%E7%B5%82%E6%AD%A2-%E6%83%9F-%E6%A9%9F%E5%9E%8B%E4%BA%AB%E7%89%B9%E4%BE%8B%E6%8F%9B%E9%9B%BB%E6%B1%A0

29. iFixit swollen-battery guide: fire/explosion risk; identification; discharge below 25% before removal — https://Www.ifixit.com/Wiki/History/What_to_do_with_a_swollen_battery?revidA=425671&revidB=425697

30. Micro Center: common swelling locations and symptoms — https://www.microcenter.com/site/mc-news/article/laptop-battery-swelling.aspx?rd=1&storeid=131

31. Electropapa (Oct 2026): swelling symptoms; power off and disconnect on discovery — https://electropapa.com/en/blog/what-to-do-with-a-swollen-battery

32. BatterySkills: wear typically after 2–4 years; US MacBook Air replacement reference — https://batteryskills.com/what-causes-a-laptop-battery-to-swell/ ; https://batteryskills.com/how-much-does-a-macbook-air-battery-replacement-cost/

33. Windows powercfg /batteryreport — https://learn.microsoft.com/en-us/answers/questions/3742508/battery-health ; https://chargie.org/windows-laptop-battery-health/

34. macOS 1,000-cycle rating, up to 80% capacity at rated cycles — https://www.turtlebar.app/guides/macbook-battery-health ; https://deepcleanmac.com/blog/how-to-check-cycle-count-on-macbook ; https://www.asurion.com/connect/tech-tips/when-its-time-to-replace-your-macbook-battery/

35. Lenovo Vantage battery tools (Charge Threshold / Conservation Mode) — https://www.solveyourtech.com/how-to-limit-battery-charge-to-80-in-windows-11-a-step-by-step-guide/ ; https://www.supportyourtech.com/tech/how-to-limit-battery-charge-to-80-on-windows-11/

36. Apple battery care (80% charge limit, 16–22°C, store at 50%) — https://vinish.dev/macbook-charging-on-hold-explained ; https://www.fastcompany.com/91532797/4-battery-charging-tips-keep-your-apple-macbook-running-longer-than-ever-charger-low-power-mode-optimized ; https://sellup.com.sg/blogs/how-to-maximize-the-lifespan-of-iPhone-battery.php

37. Lenovo official safety guide: store at 30–50%, charge yearly; wrong model risks explosion — https://download.lenovo.com/consumer/mobiles_pub/new_ml_swg_en_ja_ko.pdf

38. Emergency line: smoke/smell/heat — don't touch, evacuate, call emergency services — https://theitguysfix.com/2026/08/31/laptop-swollen-battery-safe-response-plan-2026/

39. DIY replacement risks: glued batteries, ribbon damage, warranty void — https://iphoneipadfix.com/guides/macbook-battery-replacement.html ; https://www.asurion.com/connect/tech-tips/when-its-time-to-replace-your-macbook-battery/ ; https://macosx-faq.com/how-much-replace-macbook-air-battery/

40. HP technical document c05159228 (via official community): polymer-cell swelling causes — https://h30434.www3.hp.com/t5/Desktop-Hardware-and-Upgrade-Questions/my-laptop-battery-is-swelling-and-it-is-charge-holding/td-p/8268046