How To Measure Battery Capacity?

Your battery requires repairs or replacement when its internal components start to degrade. One of the most significant factors that let you determine that is battery capacity. Recent battery statistics show that lithium-ion batteries shall dominate the market as the demand for compact and high-density batteries increase.

That’s why it’s essential to know how to measure battery capacity. It’s not like you can ship them with a meter that tells you when it’s about to run out. Your vehicle or inverter system may often cease functioning as your battery system runs out of juice at the most inconvenient time. Throughout this guide, you’ll learn about the various methods and equipment that can help you precisely determine battery capacity.

How To Measure Battery Capacity?

There are three primary ways to measure battery capacity. Those are described below in detail.

Constant Current Method

It’s a convenient procedure with little accuracy but is pretty swift and safe. You can do it by completing the circuit with a constant current load. Attach a voltmeter to ensure it operates on the battery’s rated voltage. Wait for 2 minutes and multiply the current value in Amperes by 30. It provides you with the battery capacity in Ah.

Constant Power Method

If you know the exact draw of power from a load, you can accurately predict your remaining battery capacity. Although, it does require some complicated equipment that draws constant power while remaining compatible with the battery voltage. Much like the current method, you need to measure the power drain in Watts for 2 minutes and multiply it by 30. That gives you the battery capacity in Wh.

Constant Resistance Method

The method grants you the most accurate capacity readings since it deals with the energy that the battery contains. For this, you must maintain the battery’s rated potential difference across a known resistor for 2 minutes. That lets you measure the power drain in Watts. Next, you need to multiply it by 30 to obtain the battery capacity in Wh.

What Is the Best Way To Measure Battery Capacity?

Due to its accuracy, the constant resistance method is the best to measure battery capacity. It’s how most multimeters function, so it’s always good to have one handy. Modern multimeters are highly portable; you can carry one conveniently within your dashboard or backpack.

Best Multimeter To Measure Battery Capacity

Since multimeters are your best budget to measure battery capacity on a budget, it helps to choose the appropriate one for the job. Here are our top picks for multimeters that you can order online or buy at your nearest electronics store.

AstroAI Multimeter

If you’re looking for a budget multimeter, AstroAI’s base multimeter can be the ideal choice. It costs less than $10 when you order it from Amazon and is compatible with all DC appliances. You can take up to 2000 readings over its lifespan. It comes with a dual fuse circuit to keep the user safe in the event of a short circuit.

AstroAI M4K0R Digital Multimeter

The AstroAI M4K0R is best for users who need a durable multimeter for a reasonable price. It’s bulkier than the base version but adds several functions to it. It also has a higher tolerance for measurements, as it can measure up to 600V, 10A of current, and 40 million Ohms of resistance. The M4K0R is compatible with both AC and DC devices, featuring various additional utilities, such as a flashlight and wire extenders, to make it more convenient to use.

Crenova MS8233D Auto-Ranging Digital Multimeter

This multimeter from Crenova has an auto-detection function that measures any parameter within seconds. It’s one of the most advanced devices that you can have to assess battery health. Thanks to its digital flash memory function, you can track the degradation rate of any battery, ensuring the optimal time for repairs or replacements. Not bad for a device that costs less than $27.

KAIWEETS Digital Multimeter with Case

KAIWEETS provides a digital solution for a well-balanced multimeter. It’s compact yet compatible with both AC and DC devices. The built-in safety features allow for hazard-free usage. Its lifetime warranty and technical support set it apart from other multimeters, making it the only multimeter you’ll ever need.

How To Measure Rechargeable Battery Capacity With a Multimeter?

How To Measure Rechargeable Battery Capacity With a Multimeter?

Using a multimeter to measure battery capacity is pretty straightforward.

  1. Ensure that the battery is disconnected from all circuits, and place it on an insulated surface.
  2. Connect the positive and negative ends of the multimeter to the respective terminals of the battery.
  3. Set the range of voltage to the rated voltage of the battery. If the reading is close to the rated voltage, then the battery is good to go. A battery usually gets discharged once it falls below 75% of its rated voltage.
  4. Alternatively, you can set the multimeter at a specific resistance and read the voltage. Use the values to calculate the power emitted (P=V2/R) and the energy (E=P x time) to calculate the precise capacity in Wh.

See full this video: How to check battery capacity

Frequently Asked Questions

Can a Multimeter Measure Battery Capacity?

Yes. You can use the voltage function to measure the battery capacity. If it’s close to the battery’s rated voltage, then it’s at workable capacity.

How To Calculate the Ah Rating of a Battery?

You can calculate the Ah rating by setting your multimeter to measure the energy in the range as rated for the battery. It can provide you with an accurate reading. If you don’t have a digital multimeter, you need to measure the current it can provide at a specific voltage. Take the reading for 2 minutes and multiply it by 30 to obtain the battery capacity in Ah.

What Instrument Is Used To Measure Battery Capacity?

A multimeter is often best to measure battery capacity. However, you can also use a voltmeter or ammeter, although they require some calculations to obtain accurate readings.

Can Battery Capacity Be Measured in KWh?

Yes. Heavier batteries used in solar inverters and RVs are often rated in KWh. You can set your multimeter to an adequate range to obtain precise readings.


Measuring your battery’s capacity is necessary to ensure that it’s at peak performance. We hope this guide gave you insight into how to measure battery capacity and gave you enough options for a multimeter that you can keep handy for the foreseeable future.

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