Why can a laptop battery swell even after it passes a capacity test?

Why can a laptop battery swell even after it passes a capacity test?

A laptop battery that passes a capacity test can still swell. Capacity only names how much energy the cells currently store. It does not name whether the protection board (保护板) still cuts charge on overcharge or heat, or whether internal resistance (内阻) has risen and made a local hot spot. Swelling (鼓包) is gas in the cell. That gas can form while the meter still prints a pass. Protection cut-off and internal resistance are separate rows. A capacity pass is not a swell check.

A listing that only prints a capacity reading looks finished on the meter. The chassis can still lift. Protection and internal resistance already sit as named rows on the usual battery check, beside voltage, charge/discharge, interface and load capability. A capacity pass does not tick those rows. File swell risk at selection, not after the carton is already in the lid.

Why isn't a passed capacity test a passed pack?

Capacity tells you how much energy the cells currently store. It does not tell you whether the board still opens the charge path when the pack is overcharged or hot, and it does not tell you whether a cell is already heating locally under load. A pack can still deliver a capacity number while that gas is already forming. End users feel the chassis lift even when the meter still looks green.

Buyers skip quieter rows after the loudest token. On a battery lot the loud token is a passed capacity test. Model, version and interface mix-ups on other accessory families train the same habit. No house can erase that risk. A listing can still name protection cut-off and internal resistance so the skip is visible before the carton.

If a quote only repeats the capacity number, send it back. Ask whether protection and internal resistance were named against the original pack.

What actually drives swell if capacity still reads?

Swell is gas, not a second name for a low capacity reading. A 3 December 2024 English consumer page puts heat and gas at the centre of laptop swelling, and names overcharging as the most common cause. It also records that a swollen pack may continue working. Public language already ranks it that way: the pack still runs; the cell can still balloon.

A 28 September 2025 review ties swelling to gas on overcharge, and correlates swell with both capacity fade and impedance rise. Impedance rise is the public name for a stack that is getting harder to push current through — internal resistance in the house list. That review also prints lab volume percentages. Those figures stay on that paper. Capacity fade and swell are related in the literature. They are not one meter reading, and they are not a buying table on this desk.

A 25 September 2024 paper treats a protection circuit board as a separate layer that cuts the circuit on overcharge, over-discharge or short. Capacity testing does not run that cut-off. If the confirmation — the order sheet — only names milliamp-hours, the figure that says how much charge the pack can still hold, protection is still unread.

Why are protection and internal resistance separate rows from capacity?

Protection is whether the board still opens the charge path in time. Internal resistance is whether a cell is already heating locally under load. Capacity is stored energy on a discharge. Three fields. A late cut-off or a hot spot can make gas while the discharge still meets a label. Filing that pack as “capacity passed, so safe” trains the shop to skip two rows until the palmrest lifts.

Write protection and internal resistance on the confirmation the same way capacity is written. A trial of two pieces still needs those fields. A regular five-piece lot still needs them. Mixed models do not waive them. Battery warranty on this desk is 12 months. That clock is after-sales. It does not turn a capacity printout into a swell check.

If a seller answers with “it holds charge”, they have not answered.

How should a listing split a capacity pass from protection and internal resistance?

Split stored energy from the cut-off and from the hot-spot row. The useful comparison is a capacity-only listing versus protection and internal resistance named. A green capacity meter does not move the pack onto those rows. Name both extra rows before the lot is treated as a fit.

A laptop series name is weaker than the three fields. Search capacity, then confirm protection and internal resistance still sit beside it. A “compatible equivalent” is only an equivalent after those fields still match.

Key facts

These seven facts are the ranking, not a catalogue. A capacity pass is not a swell check. Protection cut-off is a named row. Internal resistance is a named row. Gas from a late cut-off or a hot spot is how swell usually starts. A swollen pack can still run.

· Capacity only names stored energy.

· Protection is whether the board still cuts charge in time.

· Internal resistance is the hot-spot row, not a second capacity number.

· A 2024 English page already says a swollen laptop pack may continue working.

· A 2025 review already ties swell to overcharge gas and to rising impedance.

· A 2024 paper already treats the protection board as a separate cut-off layer.

· File swell risk as selection, not as a capacity pass.

What should you ask before you list or buy a lot?

Ask whether protection still cuts charge on overcharge or heat; whether internal resistance was named against the original pack; and whether the seller is only proving a capacity number. Ask for those two rows in writing, not only a milliamp-hour printout. If the seller answers with “it passed capacity”, they have not answered.

Write protection and internal resistance on the confirmation beside capacity. Mixed models can sit on one lot. A trial of two pieces still needs the same fields as a regular five-piece lot. Ordinary outbound here is 7–15 days. That clock is the buying path. It does not turn a capacity pass into a swell check.

How does this desk check capacity against protection on a battery lot?

This desk checks outgoing battery lots against named dimensions that already include capacity, internal resistance and protection, beside voltage, charge/discharge, interface and load capability. A capacity pass is not the protection row. We do not treat a capacity-only listing as a settled swell check.

We are a buying-and-shipping house, not a factory. Shenzhen Mildtrans Industrial Co., Ltd. (深圳市中川实业有限公司) has been on the mainland register since 2004. Mildtrans Industrial Co., Limited (中川实业投资有限公司) has been on the Hong Kong SAR, China register since 2010. Most receipts use the Hong Kong name. Batteries sit on our five core families.

Regular categories start at five pieces, with a trial of two, mixed models accepted. Ordinary outbound is 7–15 days. Payment through this desk is T/T — telegraphic transfer. A letter of credit is refused. Battery and adapter warranty is 12 months. None of those commercial rows replace protection versus capacity on the confirmation.

FAQ

If the pack still holds its labelled capacity, is swell risk settled?

No. Capacity is one row. Protection cut-off and internal resistance still have to be named. A pack can hold a capacity number while gas is already forming.

Can a swollen battery still run?

Yes. A 2024 English page already records that a swollen pack may continue working. Running is not the swell check. Replace the pack; do not treat a live machine as proof the cells are settled.

Why name internal resistance if I already have a capacity printout?

A 2025 review already correlates swell with impedance rise as well as with capacity fade. Impedance rise is the public name for a stack that is getting harder to push current through. That is the internal-resistance row, not a second capacity meter.

Does a 12-month battery warranty replace those two rows?

No. Warranty is after-sales. Protection and internal resistance still have to sit on the confirmation before the carton. A warranty clock does not name the cut-off.

Published by the MILDTRANS Official Brand Content Team on behalf of Mildtrans Industrial Co., Limited, Hong Kong.