How to Test An 18650 Battery With A Multimeter

An 18650 battery refers to a lithium ion rechargeable battery, and it may sometimes be called an 18650 cell. This is usually an excellent choice of battery for small devices and has a voltage rating of 3.7V and its amperage rating ranges within 1800mAh to 3500mAh.

What can be used to test the condition of an 18650 battery? A multimeter can be used to test whether an 18650 cell is in working condition provided you follow the right procedure. As a rechargeable battery, it might come in handy for you and it takes a maximum of four hours to be completely charged.

The circuit prevents the battery from overheating or overcharging and even rapid discharge. This makes the protected ones a great choice to go for over the cheap unprotected ones. You may want to test the condition of a couple of 18650 cells you have.

While there are a number of ways you can accomplish this, this article focuses on the multimeter as an instrument you can use. The following illustrations explain how to go about this.

What Tool Do You Need?

When testing an 18650 rechargeable cell you will have to obtain a number of tools depending on the type of test you want to conduct. A multimeter may come in handy, you will also need the battery’s recommended charger and the 18650 cell itself. Of course, you will need a stopwatch too.

Ways to Test 18650 Batteries With a Multimeter

A multimeter can be used to test if an 18650 battery is actually working. Even though, the multimeter will give the milliamp-hours of the battery, you can use this to check if a battery is working.

The mAh rating is measured using the multimeter and a resistor can be used to step in as a load. You will also need a stopwatch to show the elapsed duration. The procedure is as indicated below:

1. You will first start by checking the meter’s battery baby setting the multimeter’s knob at the battery check level. You will have to replace an exhausted one before going on with the process.
2. Position the 18650 battery in the holder.
3. Place the alligator clips on the meter’s probe tips.
4. You will have to go for a resistor that is appropriate for the battery’s voltage.
5. Reset your stopwatch at hand.
6. Connect the 18650 cell’s positive terminal onto one of the resistor’s leads.
7. Change the multimeter’s control knob to indicate direct current.
8. Clip the positive meter probe to the unconnected resistor lead, it is the red one. Click the black one, which is the negative probe, to the battery’s negative terminal. Confirm if the meter shows a positive reading.
9. Start your stopwatch.
10. Check the current reading for intervals of one hour. When the current drops by 30%, stop the watch.
11. Calculate the battery’s mAh rating by multiplying the number of hours recorded on the stopwatch by the initial current reading on the meter.

When working with a multimeter, you need to be keen to avoid recording improper results. First, you will have to feel the weight of each battery. A normal 18650 battery weighs not less than approximately 40 grams.

The multimeter has to be set at a high current interval, say more than the indicated mark in the introduction. Corrosion on the battery will have to be cleared using an appropriate material. You can then hold both the negative and positive probe in position.

A good 18650 cell should indicate a significant ampere level. However, if they have been significantly drained, they will indicate a lower level than this. A dead one will be in the range of 1 to 3A. However, if a cell indicates a level below 1A, you will have to dispose of it as soon as you can.

Using a multimeter is in some way a fun way of discovering how to do new things. As you learn you also get to save instead of buying new cells, you can instead just use old cells that you had disposed of and which can still work for low demanding devices.

Here is the great YouTube video I found for you below:

How Do You Use a Multimeter to Check an 18650 Battery?

Another way that a multimeter can be used to test the 18650 rechargeable cell is to check if it is accepting a full charge. This is done to see if the battery is actually charged fully whenever you place it for charging, damaged ones will not charge completely.

1. For starters, you will need to position the battery in its charger, an appropriate one, allow it charge for the recommended period.
2. Switch on your multimeter and set it to measure direct current.
3. Set the dial to measure the maximum voltage the battery can supply.
4. Touch the metal tip of the meter’s probe wire to the battery’s negative terminal and the red probe to the other terminal.

When doing this, observe the voltage reading on the multimeter, if this is less than what it should be when the battery is fully charged, then the battery might be damaged.

Related Article: How To Charge A 18650 Battery

What Should Be Careful When Testing an 18650 Battery?

When testing the 18650 cell using the multimeter, it is important to avoid electric accidents. This is because amperage, however, low they are, can be quite dangerous. They can cause complications such as heart arrhythmias and a variety of long-lasting health complications.

Basic accidents should be avoided when conducting these tests as the batteries can be rather dangerous. For instance, when dealing with a battery that is suspected to be damaged, you will need to be careful contact the chemicals from the battery with your skin as it may cause an irritating effect.

In the case of the chargers used for the rechargeable batteries, they need to be the appropriate chargers for the job. Using a wrong one may damage the battery in the process.

How to Tell If an 18650 Battery Is Bad or Good?

To test if an 18650 battery is actually in good state or not, you will need the Batlab system. This is a lab test that can be used to completely check the condition of the battery. the battery is made to run on a standard 5V power supply and it has holders for four lithium, 18650 form factor cells. The process is performed and the data recovered is analysed on a PC and a report is derived. The report indicates the cell capacity and impedance trait is figured out.

There are some physical changes on a battery that will show clearly that the battery is going bad. In the case of an 18650 cell, which is a rechargeable battery, the major ones are indicated below:

● The battery will take more hours to charge than it did initially.
● The battery may be unable to hold the charge quite long enough, this means its performance may not even be as it was before.
● Internal resistance may be developed by the battery and it will have a “bad” way.
● When checked on a meter and the battery shows a reading lower than 3, then it might be a spoilt 18650 cell.
● Bulges, dents and spoilt terminals show that the battery is damaged.
● A damaged battery gets hot while charging and discharging it.

Another simple way of testing your 18650 cell is by comparing it with a set of new ones. You can do this by comparing their voltage and discharge rate. You can also charge either, if the one in question gets too hot then it probably is damaged.

The 18650 batteries, just like any other battery, are subject to damage if they are poorly maintained. For instance, improper storage damages the battery as the environment they are kept in affects their lifetime. Having them in too cold or too hot temperatures is not advised.

In the case of 18650 cells, you should charge them with the appropriate battery charger. Using cables and other chargers will make the battery go bad.

What Voltage Should an 18650 Battery Have?

The 18650 rechargeable cell has a voltage reading of 3.7V when it is in good state. This may be altered every once in a while but it should not be significantly less than this if you want to use it for a reliable job.


The 18650 rechargeable cells have a wide variety of usage, mostly in motor vehicles and certain electronics. They can be highly reliable batteries but they need to be in good condition for them to be reliable.

As an owner, you need to know how to maintain them so that they are reliable for their whole lifetime and can perform their best when you need them to. you will have to avoid charging with the wrong charger, poor storage and subjecting them to physical damage.

1. Everything You Need To Know About The 18650 Battery – Common Sense Home