Reference · updated 10 November 2026
Battery voltage checker: is this battery still good?
Pick your battery, type the voltage your multimeter shows, and see what it means: FULL, GOOD, WEAK, or time to replace or recharge it, with the next step. The checker runs in your browser: nothing you type is sent anywhere or stored.
iPhone and iPad (iOS 17 or later): free on the App Store. Android later.
Check a battery
The checker needs JavaScript. The charts on this page show the same bands.
How to get the voltage
The checker knows AA, AAA, C, D and 9V cells, coin and button cells, rechargeable and lithium cells, and 12 V batteries. All it needs from you is the battery's resting voltage:
- Take the battery out of its device and let it rest for a minute. A car battery needs 4 hours, or 1 minute with the headlights on.
- Set the multimeter to DC volts: the V with a straight line.
- Touch the red probe to plus and the black probe to minus, and hold them still until the digits settle.
- Pick the battery above and type the reading. A minus sign counts: it means the probes are swapped.
The full method, with the safety rules, is in how to test a battery with a multimeter.
What the verdicts mean
| Verdict | What it means | What to do |
|---|---|---|
| FULL | As good as new. | Use it. |
| GOOD | Plenty left. | Use it. |
| WEAK | Most of the charge is used. | Low-drain devices only, or recharge it soon. |
| REPLACE | Empty for most devices. | Replace it and recycle the old one. |
| RECHARGE | A rechargeable battery that is empty. | Recharge it. |
| CHARGE & RETEST | A 12 V car or AGM battery that is low. | Charge it fully, let it rest, measure again. |
| OVER-DISCHARGED | A Li-ion or LiFePO4 battery below its safe minimum. | Charge it only with a charger that handles that. |
| REVERSED | A negative reading. | Swap the probes. |
| NO BATTERY | No voltage, or almost none. | Check that both probes touch metal. |
| CHECK THE BATTERY TYPE | More than this battery can read. | Pick the right battery or chemistry. |
Hearing-aid (zinc-air) cells show only OK or REPLACE.
Every chart the checker uses
These are the bands behind the verdicts. They are the same numbers the checker reads, so the charts work on their own when JavaScript is off.
Everyday cells
| Verdict | AA alkaline, AAA alkaline, C / D alkaline | 9V alkaline |
|---|---|---|
| FULL | 1.55 and up | 9.30 and up |
| GOOD | 1.45 to 1.55 | 8.70 to 9.30 |
| WEAK | 1.30 to 1.45 | 7.80 to 8.70 |
| Below Weak | under 1.30REPLACE | under 7.80REPLACE |
Measured at rest, with nothing connected. A reading exactly on a boundary counts as the higher band.
Guides: AA and AAA battery voltage, C and D battery voltage and 9V battery voltage.
Coin and button cells
| Verdict | CR2032, CR2025, CR2450, CR2016 | LR44 alkaline button | SR44 silver oxide indicative |
|---|---|---|---|
| FULL | 3.15 and up | 1.55 and up | 1.57 and up |
| GOOD | 3.00 to 3.15 | 1.45 to 1.55 | 1.53 to 1.57 |
| WEAK | 2.80 to 3.00 | 1.35 to 1.45 | 1.48 to 1.53 |
| Below Weak | under 2.80REPLACE | under 1.35REPLACE | under 1.48REPLACE |
Measured at rest, with nothing connected. A reading exactly on a boundary counts as the higher band. Indicative: few sources or a flat curve, so treat these bands as a guide.
| Verdict | Voltage at rest | What it means | What to do |
|---|---|---|---|
| OK | 1.35 V and up | Still working. | Ready for use. |
| REPLACE | under 1.35 V | Empty for most devices. | Replace it, and recycle the old one. |
Measured at rest, with nothing connected. A reading exactly on a boundary counts as the higher band. Indicative: few sources or a flat curve, so treat these bands as a guide.
Guide: CR2032 and coin cell voltage.
Rechargeable and lithium cells
| Verdict | AA NiMH, AAA NiMH | 18650 Li-ion, 21700 Li-ion | AA lithium, AAA lithium indicative | CR123A |
|---|---|---|---|---|
| FULL | 1.35 and up | 4.10 and up | 1.78 and up | 3.15 and up |
| GOOD | 1.28 to 1.35 | 3.80 to 4.10 | 1.74 to 1.78 | 3.00 to 3.15 |
| WEAK | 1.20 to 1.28 | 3.60 to 3.80 | 1.70 to 1.74 | 2.80 to 3.00 |
| Below Weak | under 1.20RECHARGE | 3.00 to 3.60RECHARGE | under 1.70REPLACE | under 2.80REPLACE |
| Lower still | – | under 3.00OVER-DISCHARGED | – | – |
Measured at rest, with nothing connected. A reading exactly on a boundary counts as the higher band. Indicative: few sources or a flat curve, so treat these bands as a guide.
Guide: NiMH rechargeable battery voltage.
12 V and large batteries
| Verdict | Car battery 12 V (flooded) | 12 V AGM | 12 V LiFePO4 indicative | 6 V lantern indicative |
|---|---|---|---|---|
| FULL | 12.60 and up | 12.80 and up | 13.40 and up | 6.20 and up |
| GOOD | 12.40 to 12.60 | 12.50 to 12.80 | 13.20 to 13.40 | 5.80 to 6.20 |
| WEAK | 12.20 to 12.40 | 12.20 to 12.50 | 12.80 to 13.20 | 5.20 to 5.80 |
| Below Weak | 12.00 to 12.20CHARGE & RETEST | 12.00 to 12.20CHARGE & RETEST | 12.00 to 12.80RECHARGE | under 5.20REPLACE |
| Lower still | under 12.00REPLACE | under 12.00REPLACE | under 12.00OVER-DISCHARGED | – |
Measured at rest, with nothing connected. A reading exactly on a boundary counts as the higher band. Indicative: few sources or a flat curve, so treat these bands as a guide.
Guide: car battery voltage chart.
Measured at rest, not under load
The checker judges the voltage of a battery with nothing connected. That is a good guide for most batteries. It cannot see a worn battery: one that reads GOOD at rest can still fail in a camera flash, a toy motor or a car starter, because its voltage drops when it has to deliver current. The flat chemistries (lithium AA, coin cells, NiMH, LiFePO4) hold their voltage until they are nearly empty, so trust a resting reading least on those. The checker says so in its result.
The same check, straight from your meter
Coming Coming in an app update. It is not in the app you can install today.
The battery tester in the TestNMeasure app does this without typing. Pick the battery, touch the probes to it, and the app reads the voltage live from a Bluetooth multimeter and shows the verdict with the next step. It uses the same bands as this page. More: Battery tester.
The app you can install today already reads a Bluetooth multimeter such as the OWON OW18B live, shows its reading large on your phone, with five stability bars that light when the reading is steady, and saves a reading with one tap.
Where the numbers come from
The bands come from battery makers' datasheets and handbooks (Energizer, Duracell, Renata, Optima), Battery University and common battery testers. They are generated from the same table the app and its tests use, so the checker, the charts and the app cannot drift apart. Bands marked indicative have fewer sources or a flat curve.
What the app does here, and what it doesn't
| What it does | Plan |
|---|---|
| Pick the battery type and see FULL, GOOD, WEAK or the end of its life from the DC volts, with the next step. | Free Coming |
| A large readout that shows which digits have settled; OL and UL are shown as OL and UL, never as a number. | Free |
| Five stability bars show when a reading is steady. | Free |
| One tap saves the current reading, with an Undo. | Free |
Not yet, or not planned
- No load test: the battery tester reads the voltage without load, so it cannot show a car battery's cranking strength.
- Reads what your meter measures; it doesn't change the meter's accuracy or ranges.
Questions
Is the battery checker free?
Yes. It needs no account and no app, and it works on a phone and on a computer.
Does the checker send my readings anywhere?
No. The page carries its own numbers and does the comparison in your browser. Nothing you type is sent to us or to anyone else, and nothing is stored.
Why do I have to pick the battery type?
Because the same voltage means different things. 1.35 V is FULL for a NiMH rechargeable AA and WEAK for an alkaline AA. A lithium AA at that voltage is empty. The size of a battery is not enough: its chemistry decides the scale.
Can it tell me if my car battery is bad?
It can tell you how charged the battery is from its resting voltage. It cannot tell you whether the battery can still crank the engine: that takes a load test. Use the car battery voltage chart for the rest time and what each value means.
Try it in the demo
A simulation of the app in your browser, with made-up readings: no meter and no install needed.
Get TestNMeasure for iPhone and iPad.
iPhone and iPad (iOS 17 or later): free on the App Store. Android later.
Questions or a meter to suggest? Mail support@testnmeasure.app.
No ad networks, no sign-up.