Why these two numbers matter and how an app automatically discovers them for your specific device

Imagine waking up one morning to find your phone barely makes it through half a day, when yesterday it lasted until evening. You check for rogue apps, restart the device, even factory reset it – but nothing helps. Your once-reliable battery now behaves like it’s several years old, depleted and degraded.

But it’s not glitching. Your battery isn’t suddenly worn out. The culprit is an over-the-air update from your phone’s manufacturer, deliberately modifying the voltage thresholds of your battery. With a few lines of code pushed to your device, your healthy battery is artificially constrained to behave like a degraded one – its available capacity slashed by software, not chemistry.

This isn’t a hypothetical scenario. It has already happened to Google Pixel owners.

Who can guarantee that Samsung, Xiaomi, OnePlus, or any other Android manufacturer won’t employ similar tactics tomorrow to your phone? Perhaps to address a safety issue they’d rather not recall. Perhaps to push users toward upgrades. Perhaps for reasons they’ll never fully disclose.

This is where knowing your battery’s actual minimum and maximum voltage becomes critical. These two numbers – objective, measurable data points – can settle the question definitively: Is your battery genuinely degraded, or has your manufacturer artificially limited it? When your phone suddenly can’t make it through the day, voltage readings don’t lie.

Why knowing the battery voltage is the most important metric of your phone

If you’ve ever looked at battery monitoring apps, you’ve seen voltage readings – numbers like 3.85V or 4.21V. But what do these numbers actually mean? Without knowing your battery’s minimum and maximum voltage, a reading of 3.7V is just… a number. Is that half-charged?

The problem is that every battery and phone is different. Even two identical phone models can have slightly different voltage characteristics. Your battery might fully charge to 4.35V while your friend’s identical phone charges to 4.40V. One might shut down at 3.6V, another at 3.7V.

Users of Google Pixel phones would especially like the BatteryVoltageDisplay app since Google plays with battery max voltage through the phone’s life. First that was an emergency measure, but now it is an always active feature.

Why you need your battery’s specific numbers

Knowing your battery’s actual minimum and maximum voltage transforms those mysterious voltage readings into useful information:

Understanding Current Battery State: If you see your phone is at 3.8V, and you know your battery ranges from 3.6V (empty) to 4.3V (full), you can calculate you’re at roughly 44% charge. Lithium-ion batteries used in portable electronics have roughly linear discharge curve, making the voltage reading a reliable source of real capacity left, The battery percentage your phone shows might be wrong due to calibration issues, but voltage doesn’t lie.

Detecting Battery Problems: Your phone says it’s charged to 100%, but the voltage reads 4.1V when you know it should reach 4.35V? Your battery is faulty. The described example may come because of increased internal resistance of the battery. Without knowing your maximum voltage, you’d never catch this.

Knowing Your Real “Empty” Point: When your battery approaches its minimum voltage – say 3.65V when your minimum is 3.6V – you know shutdown is imminent regardless of what the percentage says. This is critical when you’re far from a charger and need to know your actual remaining time. This also helps to know when your phone shuts down if it has degraded battery. At this moment the phone may be showing incorrect battery percentage.

Verifying Battery Replacements: Had your battery replaced at a repair shop? Check if the voltage characteristics match your original battery. If the new battery has a significantly different maximum voltage, you might have received a unit meant for a different device model.

Comparing Manufacturer Specifications: Phone manufacturers sometimes publish battery voltage specs. Knowing your actual values lets you verify your device matches specifications or identify if something is wrong with your unit. Overcharging of Li-ion battery may lead to it catching on fire.

Google’s battery voltage manipulation: from emergency fix to standard practice

The importance of knowing your battery’s maximum voltage has taken on new significance with Google’s increasingly aggressive battery management policies on Pixel devices.

The Pixel 4a crisis

In January 2025, Google issued a mandatory firmware update for the Pixel 4a as part of what they called the “Battery Performance Program.” The company was initially vague about the reasons, but an Australian recall notice in March revealed the truth: batteries posed a risk of fire.

The update enabled lowering the maximal battery voltage, thus reducing battery capacity. Initially, the Pixel 4A firmware charged battery to 4.44 volts to display a 100% charge. But the problematic Pixel 4A update lowered that number to 3.95 volts.

That is, if the Pixel 4A initially worked in the battery voltage range of 3.7-4.44 volts, after the problematic update, it started working in the range of 3.7-3.95 volts.

This is a change that reduces the battery capacity by almost half. Instead of 3080 mAh, only 1539 mAh left available to the user.

By July 2025, the problem had spread to the Pixel 6a. Google confirmed another mandatory update that would reduce battery capacity after the battery reached 400 charge cycles. The system displayed a warning when cycle count reached 375 and actively reduced charging voltage after 400 cycles. While Google hasn’t officially published the exact voltage reduction figures for the Pixel 6a, reports suggest it received similar treatment to the Pixel 4a.

For Pixel 6a owners, this meant their phones’ batteries would be deliberately limited in capacity after roughly 13 months of daily charging. The maximum voltage – and therefore capacity – would be permanently reduced.

Pixel 10: mandatory voltage limiting

What began as an emergency response to the Pixel 6a’s problems has evolved into standard operating procedure for Google’s newest Pixel phones.

Enter “Battery Health Assistance” – a feature that lowers the battery’s maximum voltage in stages starting at 200 charge cycles and another one after 1000 charge cycles. Google describes this as helping “stabilize battery performance and aging.”

On older Pixel models (Pixel 6a, 7, and later), users could disable this feature if they wanted full battery capacity. But that option has disappeared.

For the Pixel 10 series, Battery Health Assistance is forced on and cannot be disabled.

This means every Pixel 10 owner will experience progressive battery capacity reduction starting at approximately 6-7 months of daily use (200 cycles). The phone will charge to a lower maximum voltage with each passing month, directly reducing the available capacity.

Critics point out the forced nature and performance degradation over time can be considered planned obsolescence. Unlike normal battery aging – which is chemical and inevitable – this is intentional software-enforced limitation.

For Pixel 10 owners, knowing your battery’s actual maximum voltage becomes critical for understanding what Google’s system is doing to your device.

When you first get a Pixel 10, you might measure a maximum voltage of 4.45V. After 200 cycles, you might notice it only charges to 4.35V. After 800 cycles, maybe 4.20V. Each reduction directly corresponds to less usable capacity – your phone will die faster even though the battery itself may be chemically healthy.

Without monitoring actual voltage, users only see mysteriously declining battery life and assume their battery is wearing out. With voltage data, you can see exactly when and how much Google’s Battery Health Assistance has reduced your capacity.

How to read minimum and maximum battery voltage

You can’t just look the min and max voltage up in settings – Android doesn’t display this information. You could utilize an app that shows real-time voltage reading and manually monitor voltage readings and wait for your phone to reach 1% and 100%, recording the values yourself. But this is tedious and error-prone.

A BatteryVotageDisplay monitoring app automatically detects and records min and max battery voltage while you are daily using your phone. Download it on F-Droid app store: https://f-droid.org/en/packages/com.example.timenotification

Note: The app requires at least one near-complete discharge (to 1% or below) and one full charge (to 100% maintained for at least 60 seconds) to determine both values. Until then, voltage readings are displayed without the context of minimum and maximum reference points.

App’s detection algorithm for minimum voltage

Finding minimum voltage is hard, because Android phone immediately shuts down when it reaches 0%. This means the app may be killed by Android before the app will have a chance to get a min voltage reading.

App’s author utilized a conceptually simple approach wait until the battery is nearly empty and record the voltage on its every change.

When the battery level drops to 1% – the critical zone just before phone automatic shutdown – app strarts continious recording of the voltage.

App doesn’t just record the first reading at 1%. The algorithm maintains a stored minimum value and compares every new low-battery reading against it. If a lower voltage is detected, it updates the stored value. This ensures that the true minimum is captured – not just the value when phone hits 1%. And that guarantees the min voltage will be recorded before phone shuts down.

This measurement represents the voltage at which your phone’s protection circuitry will force a shutdown due to low charge. It’s the real “zero” point for your specific phone.

App’s detection algorithm for maximum voltage

Maximum voltage detection is far more simple because normally when phone is fully charged, it does not shut down unexpectedly.

Here is the trick when your phone shows 100%, the battery is still charging – its just you don’t know about that. But look at battery voltage – it continues rising slowly for several more minutes. Modern charging systems display 100% early, then trickle charge to the actual maximum. The voltage might read 4.28V, then 4.30V, then 4.32V over the next five minutes before stabilizing at 4.35V.

If the algorithm simply recorded the voltage the moment it saw 100%, it would capture an incomplete charge state, not the true maximum.

This approach elegantly solves the trickle-charging problem. It captures the genuine maximum voltage – the stable value your battery reaches when truly full – not a mid-charging snapshot.

Continuous background operation

The app runs as a foreground service, getting voltage reading on its change. This strikes a balance: it is enough to catch voltage changes during both charging (when voltage rises slowly) and discharging (when it can drop quickly under heavy use), but avoiding unnecessary readings as it would occur on a fixed timer intervals. This makes the app not to significantly drain the battery being monitored.

The detected minimum and maximum values are stored in the device’s shared preferences, persisting across app restarts and reboots. Once determined, you have these reference points permanently – unless you deliberately reset them.

Practical usage of battery voltage

The app displays current voltage alongside your recorded minimum and maximum in a persistent notification. This turns every voltage reading into contextual information.

Seeing “3.92V” alone tells you nothing. Seeing “3.92V (Min: 3.60V, Max: 4.35V)” tells you exactly where you are: roughly 55% of your battery’s actual capacity, regardless of what the percentage indicator claims.

When the numbers reveal problems

Once you know your minimum and maximum, deviations become meaningful:

• Phone dies at 3.7V when your recorded minimum is 3.6V? The battery has degraded and has to be replaced.
• Phone claims 100% but voltage only reaches 4.1V when your maximum is 4.35V? Your battery is failing.
• A voltage reading suddenly drops? Possibly low temperature effects, high power draw or both.

The value of two simple numbers

Minimum and maximum voltage are just two data points, but they’re the foundation for understanding everything your battery does. These are the most important numbers for any battery, and they are actually printed on its case.

You don’t need to understand electrochemistry or battery physics. You just need to know: this is empty, this is full, and here’s where I am right now. The BatteryVotageDisplay app handles the complex detection logic automatically, requiring only that you once charge to 100% and discharge to zero.

The min and max battery voltage values will remain stable throughout the phone’s life. They’re characteristic of your specific battery and the battery related circuitry in your device. Once discovered, they become your personal reference points for interpreting any voltage reading.

In an era where smartphones deliberately provide less transparency about their internal workings, knowing your battery’s minimum and maximum voltage returns a small measure of control – turning mysterious numbers into actionable information.