Stable battery-percentage display depends on the cell, protection board, phone communication and real-device compatibility.

I have worked with mobile phone batteries for more than 20 years. During that time, I have received many reports that sound similar:

“The battery percentage stays at the same number for a long time.”
“It suddenly drops from 30% to 5%.”
“The phone shuts down even though it still shows power.”
“After restarting, the battery percentage changes.”
“The phone charges from zero again after shutting down.”

To the user, these symptoms may look like one simple problem: a bad battery.

Sometimes the battery is the cause.

But not always.

The percentage displayed on a phone is not measured like the fuel level in a transparent container. The phone cannot look inside the battery and directly see how much energy remains. Instead, the battery and phone estimate the remaining power using electrical measurements, stored data, software calculations and communication between several components.

That system may involve:

• Cell voltage

• Charging and discharging current

• Battery temperature

• Battery capacity data

• Internal resistance

• Protection-board information

• Battery communication

• Phone operating system

• Previous battery records

• User behaviour
  

When one part of this system is inaccurate or incompatible, the number on the screen may no longer match the battery’s actual condition. After two decades on the factory floor, I have learned that a stable battery percentage is not created by the cell alone. It is created by the cell, protection board, connector, software and phone working together.

1. The Battery Percentage Is an Estimate

A phone normally estimates the remaining charge by analysing information such as:

• Battery voltage

• Current entering or leaving the battery

• Temperature

• Estimated full-charge capacity

• Previous charge and discharge behaviour

• Battery identification data

• System power consumption
  

This estimation process is often called state-of-charge calculation. The phone may combine several methods

rather than relying on one measurement. Voltage provides useful information, but voltage alone cannot always show the exact remaining capacity.

A battery under heavy load may show a temporary voltage drop. When the load is removed, the voltage may recover. Temperature can also affect voltage and power-delivery behaviour.

For this reason, the phone continuously updates its estimate. When the battery, protection board and phone communicate correctly, the displayed percentage should generally change in a stable and reasonable way. When they do not, the percentage may freeze, jump or become inconsistent.

1. Why Voltage Alone Cannot Give an Exact Percentage

Battery voltage does not decrease in a perfectly straight line, so percentage estimation requires more than one voltage reading.

Many people assume that battery percentage is calculated like this:

• High voltage means full.

• Low voltage means empty.

The basic relationship is true, but the real behaviour is more complicated. A lithium-ion battery’s voltage does not decline in a perfectly straight line from 100% to 0%.

The voltage curve may change according to:

• Battery chemistry

• Cell design

• Discharge current

• Temperature

• Internal resistance

• Battery age

• Resting time

• Phone workload

During heavy use, the voltage may temporarily fall. During rest, it may recover. This is why a phone can sometimes display a different percentage after restarting or after being left unused for several minutes.

The phone is receiving new information and recalculating its estimate. A small correction may be normal.

A large or repeated jump requires investigation.

3. Cell Consistency Is the Foundation

Stable percentage behaviour begins with consistent battery cells and controlled incoming materials.

The cell is responsible for storing and delivering energy. If the cell has unstable capacity, abnormal internal resistance or excessive self-discharge, the phone may struggle to estimate the remaining power correctly.

Possible cell-related causes of percentage problems include:

• Capacity below specification

• Abnormal internal resistance

• Unstable voltage under load

• Excessive voltage recovery

• Poor batch consistency

• Cell aging

• Internal damage

• Abnormal self-discharge

• Incorrect cell specification

At Longhehui, incoming cell inspection may include:

• Appearance

• Dimensions

• Thickness

• Voltage

• Internal resistance

• Batch identification

• Storage condition

• Specification confirmation
  

A protection board can process information, but it cannot make an unstable cell behave like a stable one.

The quality of the percentage display still begins with the cell.

4. Internal Resistance Can Cause Sudden Shutdown

High or unstable internal resistance can cause voltage to drop sharply when the phone demands more power.

A battery may still contain some energy but be unable to deliver enough power at a particular moment. This often happens when internal resistance is too high.

When the phone performs a demanding task, such as:

• Opening the camera

• Recording video

• Gaming

• Making a video call

• Using navigation

• Connecting to a weak mobile network

• Increasing screen brightness

the current demand may rise. If the battery cannot deliver that current efficiently, its voltage may drop quickly. The phone may interpret the low voltage as an empty or unsafe battery and shut down.

After the phone turns off, the load disappears. The battery voltage may then recover. When the phone is restarted, it may display a different percentage.

This can create a confusing symptom:

• The phone shuts down at 20%, but after connecting the charger, it shows power again.

• The battery may still contain energy, but it could not deliver that energy stably under load.

• This is why capacity and internal resistance must be tested together.

5. The Protection Board Controls More Than Safety

The protection board may manage protection, temperature sensing, battery information and communication with the phone.

Many buyers think the battery protection board only prevents short circuits. Its role may be much broader.

Depending on the battery model, the PCBA may support:

• Overcharge protection

• Over-discharge protection

• Overcurrent protection

• Short-circuit protection

• Temperature sensing

• Battery identification

• Charge and discharge data

• Capacity information

• Communication with the phone

• Battery-health information

• Percentage calculation support
  

Different phone brands and models use different battery-management designs. Some batteries use

relatively simple protection systems. Others require more complex communication between the battery and phone.

This is why a good cell does not automatically guarantee stable percentage display. If the PCBA information is incorrect, incomplete or incompatible, the phone may calculate the remaining power incorrectly.

6. Decoding and Communication Compatibility Matter

For compatible models, decoding and communication functions must be verified in addition to basic charging and discharging.

Some modern phones exchange identification and status information with the battery.

Depending on the model, the phone may read information such as:

• Battery identity

• Cycle data

• Capacity information

• Temperature

• Charge status

• Battery health

• Authentication or communication status
  

If the replacement battery does not communicate correctly, the phone may display:

• An unknown-part notification

• Incorrect battery health

• Missing battery data

• Unstable percentage

• Charging warnings

• Abnormal restart behaviour
  

The exact behaviour depends on the phone model and operating-system version. For this reason,

factories must not assume that one PCBA version will work perfectly across every

production period or software update.

Real-phone verification is important, especially when:

• A new phone model is introduced

• The PCBA design is updated

• A new decoding solution is used

• The phone operating system changes

• Customers report repeated compatibility issues
  

7. Connector Quality Can Affect the Displayed Percentage

Stable electrical contact is necessary for accurate voltage, current and communication signals.

The connector carries power and, in many designs, communication signals between the battery and phone.

A connector problem may cause:

• Intermittent charging

• Charging interruption

• Sudden shutdown

• Percentage jumps

• Battery not recognised

• Phone restarting

• Unstable temperature reading

• Communication failure
  

Possible causes include:

• Connector not fully seated

• Bent contacts

• Damaged flex cable

• Incorrect connector height

• Contamination

• Misalignment

• Weak soldering

• Installation damage
  

A connector can look normal from the outside while still creating unstable contact. This is why inspection should include both appearance and functional testing.

8. Welding and Internal Connections Must Remain Stable

Stable welding and internal connections help prevent intermittent voltage and power loss.

Inside the battery, the cell and PCBA are connected through small conductive areas.

If the welding is weak, inconsistent or damaged, the battery may pass an initial test but fail later during:

• Transportation

• Installation

• Vibration

• Repeated charging

• Phone drops

• High-current use

A poor internal connection may create intermittent resistance. The phone may then receive unstable voltage or communication data.

Possible symptoms include:

• Percentage freezing

• Percentage jumping

• Charging stopping and restarting

• Random shutdown

• Phone restarting

• Battery recognised only sometimes
  

The welding area is hidden inside the completed battery, so process control is essential.

Inspection may include:

• Welding position

• Welding strength

• Tab alignment

• Surface condition

• Electrical continuity

• Insulation

• Flex cable position
  

A defect only a few millimetres wide can create a serious customer complaint.

9. Capacity Data Must Match the Battery’s Real Performance

Actual capacity testing helps ensure that battery data and real discharge performance remain consistent.

The phone’s percentage estimate depends partly on its understanding of the battery’s usable capacity. If a battery is labelled or programmed with one capacity but actually delivers much less, the percentage calculation may become inaccurate.

For example, the phone may assume that more energy remains than the cell can actually provide.

This can lead to:

• Percentage falling slowly at first

• Rapid decline near the end

• Shutdown before reaching 0%

• Large percentage correction after restart

• Charging percentage rising unusually quickly
  

Capacity testing should therefore confirm:

• Actual discharge capacity

• Charging capacity

• Discharge time

• Voltage curve

• Cut-off behaviour

• Batch consistency
  

The printed or stored capacity must remain realistic. A large number does not help the customer if the battery cannot deliver it.

10. Aging Helps Expose Unstable Voltage

Aging and voltage reinspection help identify abnormal self-discharge and unstable batteries before shipment.

Some batteries perform normally immediately after production but change after standing for a period of time.

Aging can help reveal:

• Abnormal self-discharge

• Voltage loss

• Internal-resistance change

• Unstable protection-board behaviour

• Swelling

• Appearance changes

• Charging abnormalities
  

Depending on the production plan, the factory may record voltage before and after aging. A battery with abnormal voltage loss may later create percentage problems in the customer’s phone. The purpose of aging is to allow that instability to appear before shipment.

11. Calibration May Be Needed After Battery Replacement

After replacement, the phone may need time and normal charge cycles to update its battery estimate.

After a new battery is installed, the phone may initially use information learned from the old battery.

The old battery may have had:

• Lower capacity

• Higher internal resistance

• Different voltage behaviour

• Severe aging

• Unstable percentage history
  

The phone’s software may need time to update its estimate based on the new battery’s behaviour. In some cases, one or more normal charge and discharge cycles may improve percentage accuracy. However, calibration should not be used to excuse serious symptoms.

Calibration may be reasonable when:

• The percentage is only slightly inaccurate

• The battery otherwise charges normally

• There is no abnormal heat

• There is no swelling

• The phone does not repeatedly shut down

• The behaviour improves after normal use
  

Calibration is not an acceptable answer when:

• The phone repeatedly shuts down with significant power remaining

• Percentage jumps are large and frequent

• Charging repeatedly stops

• The battery becomes abnormally hot

• The battery is swollen

• The battery is not recognised

• The problem appears across multiple phones
  

In those cases, the battery and phone should be tested

12. Restarting the Phone Can Change the Estimate

A restart may cause the phone to recalculate battery information, but large repeated changes require investigation.

When a phone restarts, the operating system reloads battery information and may recalculate the percentage.

A small change can occur because:

• The battery has rested

• Voltage has recovered

• Background load has stopped

• The operating system has updated its estimate

• New battery information has been read

A large repeated change may indicate:

• High internal resistance

• Unstable voltage

• Incorrect capacity data

• Communication problems

• PCBA incompatibility

• Poor electrical contact

• Aged phone hardware

• The important point is repetition.

One small correction after battery replacement is different from a phone that changes from 40% to 10% every time it restarts.

13. The Phone Itself May Be Part of the Problem

Battery complaints should also consider the condition of the phone’s charging circuit, mainboard and connector.

A replacement battery may reveal problems that already existed in the phone.

Possible phone-related causes include:

• Damaged charging circuit

• Worn battery connector

• Mainboard leakage

• Charging-port damage

• Water damage

• Previous repair damage

• Software errors

• Excessive background power consumption

• Temperature-sensor problems

• Device aging
  

If several batteries show the same symptom in one phone, the phone should be investigated. Similarly, testingone battery in several known-good phones can help determine whether the issue follows the battery

or remains with the device. This comparison is more reliable than replacing parts repeatedly without testing.

14. Installation Quality Affects Battery Communication

Correct installation helps maintain stable power, communication and temperature signals.

A replacement battery should be installed carefully.

Possible installation problems include:

• Connector not fully seated

• Connector pressed at an angle

• Insulation damaged

• Battery compressed

• Screws installed incorrectly

• Shielding missing

• Adhesive applied unevenly

• Phone housing deformed
  

The technician should confirm:

• Correct battery model

• Correct connector position

• Stable connection

• No physical pressure

• No damaged insulation

• Normal startup

• Normal charging

• Stable percentage

• Normal temperature
  

A battery should not be forced into a phone when its dimensions, connector or flex cable do not match correctly.

15. Operating-System Updates Can Affect Compatibility

Battery compatibility testing should record both the phone model and operating-system version.

Phone manufacturers periodically update operating systems and battery-management behaviour.

An update may change:

• Battery recognition

• Health information

• Warning messages

• Charging behaviour

• Background power management

• Percentage estimation

• Communication requirements
  

A replacement battery that performed normally under one software version may require verification under a newer version. This does not mean every update creates a problem. It means compatibility records should include the software environment.

When a customer reports a percentage issue, useful information includes:

• Phone model

• Model region

• Operating-system version

• Battery model

• PCBA version

• Installation date

• Date the issue began
  

This information helps the factory reproduce the correct condition.

16. Real-Phone Testing Is Necessary

Real-phone testing verifies recognition, charging, percentage behaviour

and shutdown performance in the intended device.

Electrical testing equipment can verify:

• Voltage

• Capacity

• Internal resistance

• Charging

• Discharging

• Protection functions
  

But it cannot completely reproduce every phone’s communication, software and power-management behaviour.

Real-phone testing may include:

• Battery recognition

• Startup

• Charging from low percentage

• Percentage progression

• Standby

• Video playback

• Camera use

• Controlled high-load use

• Restart

• Low-power shutdown

• Temperature behaviour
  

Technicians should observe whether:

• Percentage rises steadily during charging

• Percentage declines reasonably during use

• The phone shuts down near the expected low-power point

• The percentage changes abnormally after restart

• Charging stops unexpectedly

• The battery is recognised correctly
  

17. How We Reproduce a Percentage Complaint

Complaint analysis combines customer evidence, production records and controlled repeat testing.

When a customer reports that the percentage freezes, jumps or causes shutdown, the factory should collect complete information.

Useful details include:

• Battery model

• Phone model

• Operating-system version

• Battery front and back photographs

• Connector photograph

• Installation date

• Charger information

• Starting percentage

• Percentage when shutdown occurs

• Whether the issue occurs under load

• Whether the percentage changes after restart

• Whether charging is normal

• Whether the battery becomes hot

• Whether the battery is swollen

• Batch or order information
  

The factory can then review:

• Cell batch

• PCBA version

• Production date

• Capacity results

• Internal-resistance results

• Aging records

• Retained samples

• Previous complaints

• Real-phone compatibility
  

If the returned battery is available, testing may include:

• Appearance inspection

• Voltage

• Internal resistance

• Capacity

• Charging

• Discharging

• PCBA communication

• Connector inspection

• Real-phone testing

• Low-percentage shutdown verification

The goal should be to reproduce the customer’s symptom under controlled conditions.

What 20 Years of Manufacturing Has Taught Me

Experience becomes valuable when symptoms are supported by electrical measurements and repeatable testing.

After more than 20 years in battery manufacturing, these are the principles I trust most.

The percentage on the screen is not the battery itself

It is an estimate created from electrical data, communication and software.

Capacity alone is not enough

A battery must also deliver power with stable voltage and acceptable internal resistance.

A good cell needs a compatible PCBA

The phone, cell and protection board must work together.

A restart is a clue, not a diagnosis

A changed percentage after restart may reveal voltage recovery, recalculation or communication instability.

Real-phone testing is essential

Testing equipment provides controlled data, but only the intended phone can confirm system compatibility.

Installation cannot be ignored

A damaged connector or poor connection can imitate a defective battery.

Complaints require evidence

Phone model, software version, batch records and returned-sample testing help identify the real cause.

Experience must become a repeatable process

A technicians judgement is valuable, but it should be supported by specifications, records and controlled tests.

How Longhehui Controls Percentage Stability and Phone Compatibility

Longhehui evaluates the cell, protection board, capacity and real-device behaviour as one complete system.

At Longhehui, battery-percentage stability is evaluated as part of a complete manufacturing and quality-control process developed through more than 20 years of industry experience.

Depending on the battery model and customer requirement, our process may include:

• Incoming cell inspection

• Voltage measurement

• Internal-resistance testing

• Capacity grading

• PCBA function verification

• Connector inspection

• Communication and decoding testing

• Aging

• Voltage reinspection

• Charging and discharging testing

• Real-phone compatibility testing

• Operating-system verification

• Batch traceability

• Returned-product analysis
  

Our objective is not simply to manufacture a battery that turns the phone on. Our objective is to provide a battery whose power delivery, percentage display, charging behaviour and phone compatibility can be tested and explained.

Looking for Replacement Batteries with Stable Phone Compatibility?

Longhehui supports overseas importers, distributors, wholesalers, repair chains and private-label battery brands.

Our services include:

• Replacement mobile phone battery wholesale

• OEM and private-label manufacturing

• Custom labels and packaging

• Battery model development

• Capacity verification

• Internal-resistance testing

• PCBA and decoding verification

• Real-phone compatibility testing

• Operating-system compatibility review

• Batch traceability

• Technical after-sales analysis
  

When contacting us, please provide:

• Required battery models

• Target phone models

• Target market

• Estimated order quantity

• Required capacity

• Packaging requirements

• Phone software requirements

• Required testing or documentation
  

Our team will review your application and recommend an appropriate production and quality-control plan.

Longhehui Technology
Mobile Phone Battery Manufacturer and Wholesale Supplier
Website: longhehui.com