Enter the voltage your multimeter reads and this free battery voltage checker tells you if the battery is full, weak or dead, and roughly how much charge is left. It works for AA, AAA, C and D alkaline batteries, NiMH rechargeables, 9V batteries, CR2032 coin cells, LR44 button cells and 18650 lithium-ion cells. You will find a voltage chart for each type below the checker.
Check your battery’s voltage
Pick the battery type, then enter the voltage your multimeter shows with nothing connected to the battery.
How to Check Battery Voltage with a Multimeter
Any digital multimeter can test a battery in a few seconds. Take the battery out of the device first so you get a clean no-load reading.
- Plug the black lead into the COM jack and the red lead into the VΩ jack. Never use the A or mA jack for this test.
- Turn the dial to DC volts. It is the V with a straight line and dashes above it (V⎓). On a manual-range meter, pick 20V. The 2V range shows one more decimal place for 1.5 V cells. See multimeter symbols if you are not sure which one it is.
- Touch the red probe to the positive (+) end and the black probe to the negative (–) end. On an AA cell the + end has the bump. On a coin cell the + side is the flat face with the writing on it.
- Read the display and enter the number in the checker above. A minus sign only means the probes are reversed. The voltage is still correct.
- If the battery reads fine but the device still does not work, do a load test (explained below).
New to multimeters? Our beginner’s guide to using a multimeter covers the dial, the jacks and safe probing.
Battery Voltage Charts
These charts show no-load readings at room temperature. Cold batteries read a little lower, and a battery that was just in use reads lower for a few minutes, then recovers a little.
AA, AAA, C and D Alkaline Battery Voltage Chart
| Reading (no load) | Status | Approx. charge |
|---|---|---|
| 1.55 V and above | Full (new) | 90–100% |
| 1.40 to 1.54 V | Good | 60–90% |
| 1.25 to 1.39 V | Weak | 20–60% |
| 1.00 to 1.24 V | Nearly empty | under 20% |
| Below 1.00 V | Dead | 0% |
A new alkaline battery reads about 1.6 V, which is more than the 1.5 V on the label. That is normal. The label shows the average voltage over the battery’s life, and the voltage slowly falls as it is used. Battery makers rate alkaline cells down to 0.8 V under load, but most devices stop working well before that, at around 1.0 to 1.1 V.
NiMH Rechargeable AA and AAA Voltage Chart
| Reading (no load) | Status | Approx. charge |
|---|---|---|
| 1.40 V and above | Just charged | 100% (settles within a few hours) |
| 1.32 to 1.39 V | Full | 90–100% |
| 1.26 to 1.31 V | Good | 50–90% |
| 1.20 to 1.25 V | Medium | 20–50% |
| 1.10 to 1.19 V | Low | 5–20% |
| 0.90 to 1.09 V | Empty | 0–5% |
| Below 0.90 V | Over-discharged | Recharge and check it holds a charge |
A NiMH battery reading 1.2 V is not weak. That is its normal working voltage. It stays close to 1.2 V for most of its charge, while an alkaline cell falls steadily from 1.6 V, which is why a half-used alkaline and a fresh NiMH can read about the same.
9V Battery Voltage Chart
| Reading (no load) | Status | What to do |
|---|---|---|
| 9.2 to 9.6 V | Full (new) | Use anywhere |
| 8.5 to 9.1 V | Good | Fine for most devices |
| 7.5 to 8.4 V | Weak | Replace in smoke alarms. Use up in toys or remotes. |
| 5.4 to 7.4 V | Nearly empty | Replace |
| Below 5.4 V | Dead | Recycle. Near 0 V can mean an internal short. |
Rechargeable 9V batteries are made differently. A NiMH 9V is usually rated 8.4 V and a lithium-ion 9V is about 7.4 V, so judge them by the voltage printed on the label. For those types and a step-by-step load test, read how to test a 9V battery with a multimeter.
CR2032 Coin Cell Voltage Chart
| Reading (no load) | Status | Approx. charge |
|---|---|---|
| 3.0 V and above | Good | 50–100% |
| 2.8 to 2.99 V | Used | 20–50% |
| 2.5 to 2.79 V | Weak | 5–20% |
| 2.0 to 2.49 V | Nearly empty | under 5% |
| Below 2.0 V | Dead | 0% |
A new CR2032 reads about 3.0 to 3.3 V. Coin cells hold close to 3 V for most of their life and then drop quickly near the end, so a reading under 2.8 V means the cell is well used. Key fobs, kitchen scales and motherboard CMOS clocks often start to fail around 2.5 V.
LR44 Button Cell Voltage Chart
| Reading (no load) | Status | Approx. charge |
|---|---|---|
| 1.50 V and above | Good | 70–100% |
| 1.35 to 1.49 V | Used | 30–70% |
| 1.20 to 1.34 V | Weak | 10–30% |
| 1.00 to 1.19 V | Nearly empty | under 10% |
| Below 1.00 V | Dead | 0% |
18650 Lithium-Ion Battery Voltage Chart
| Resting voltage | State of charge |
|---|---|
| 4.20 V | 100% |
| 4.00 V | 90% |
| 3.90 V | 80% |
| 3.80 V | 70% |
| 3.70 V | 60% |
| 3.60 V | 50% |
| 3.50 V | 40% |
| 3.40 V | 30% |
| 3.20 V | 20% |
| 3.00 V | 10% |
| 2.50 V | 0% (empty) |
Lithium-ion cells need a little more care than other batteries:
- A full cell reads 4.2 V. Anything above about 4.25 V means it was overcharged, so check the charger.
- Below 2.5 V the cell may be damaged. Do not charge it in a normal charger. Recycle it instead.
- For storage, keep cells at about 3.6 to 3.7 V (roughly half charged).
- Stop using any cell that is swollen, dented, hot or has a torn wrapper, whatever the voltage.
No-Load vs Under-Load Voltage
A multimeter on DC volts draws almost no current, so it shows the battery’s resting (no-load) voltage. A tired battery can show a healthy number at rest and then collapse as soon as a device asks it for current. This is the most common reason a battery “tests good” but the device still will not work.
To check, measure the battery while it is powering the device, for example a torch that is switched on. A good alkaline AA drops only a little, often to around 1.3 V or more under a light load. If the reading falls a long way (for example from 1.45 V to under 1.1 V), the battery is worn out even though the no-load reading looked fine. Some multimeters have a battery test setting (marked 1.5V and 9V, or BATT) that adds a small load for you.
Why Does a New Battery Read Higher Than Its Label?
The voltage printed on a battery is its nominal voltage, an average over its working life. A fresh battery starts above that number and ends below it:
- 1.5 V alkaline: about 1.6 V new
- 1.2 V NiMH: about 1.4 V straight off the charger
- 9V alkaline: about 9.5 V new
- 3 V CR2032: about 3.2 V new
- 3.6 to 3.7 V lithium-ion: 4.2 V fully charged
So a reading slightly above the label is a good sign, not a fault.
Frequently Asked Questions
What voltage is a dead AA battery?
An alkaline AA battery is dead for most devices at about 1.0 to 1.1 V with no load, and below 1.0 V it should be recycled. A NiMH rechargeable AA is empty at about 1.0 V and just needs recharging.
What should a new AA battery read on a multimeter?
A new alkaline AA or AAA usually reads 1.55 to 1.65 V. A NiMH rechargeable reads 1.4 V or more straight off the charger and settles to about 1.3 V. A lithium AA reads about 1.8 V.
At what voltage is a 9V battery dead?
Replace a 9V alkaline battery in a smoke alarm once it reads below about 7.5 V. Most other devices stop working between 6 and 7 V, and below about 5.4 V the battery is completely flat.
When should I replace a CR2032 coin cell?
A new CR2032 reads about 3.0 to 3.3 V. Replace it when it reads below about 2.5 V, or sooner if the device shows a low-battery warning. Coin cells hold their voltage for most of their life and then drop quickly.
What is the minimum safe voltage for an 18650 battery?
Most 18650 cells should not go below 2.5 V (some are rated 2.75 V). A cell that has dropped below 2.5 V may be damaged, so do not recharge it in a normal charger. A fully charged cell reads 4.2 V.
Can I test a battery on the resistance or current setting?
No. Always use DC volts. On the current (A or mA) setting the multimeter is almost a short circuit, so touching it across a battery can blow the meter’s fuse and heat the battery. The resistance setting gives a meaningless reading on a battery.
Is the battery percentage from voltage exact?
No. Voltage gives a good guide to full, weak or dead, but the exact percentage depends on the brand, the temperature and how recently the battery was used. A load test tells you more about a battery that reads fine but does not work.
Can this tool check a 12V car battery?
No. Car batteries are lead-acid and need a different chart. Use the free car battery health checker, which also checks cranking and charging voltage.