How To Charge 18650 Li-Ion Battery Correctly? Tips to extend the life of a 18650 battery

Li-ion battery has become the most popular type of battery used in electronic devices like smartphones and laptops.

Many people believe that we can protect the lifespan of this battery just by avoiding charging overnight. That’s true, but not enough.

Have you known how to charge your best 18650  li-ion battery in a proper way? Let’s look through the following tips to see if you got enough knowledge.

1. Charge your device partially in a short time period:

Most of us have the same mistakes:

  • Remain to charge after the capacity reaches 100%
  • Always fully charge the device
  • Continuously charge until the battery is full

All of the above charging habits are actually extremely harmful to your battery life.

First of all, “too much” of everything is bad. The same happens to the li-ion battery when it continues to be charged after being full.

Some researchers found out that when your battery reaches 100%, the charger will have to maintain a small constant current to prevent the capacity from declining while being charged. This will force the battery to move constantly between “receive” and “release” energy, putting huge pressure on it.

Secondly, it was proved that li-ion batteries aren’t suitable for a full charge. Instead, you can charge it any time, anywhere you want. You even preferred to charge partially in short periods of time, like 10-30 mins.

The reason is that li-ion batteries tend to increase the constant voltage as the capacity goes up to 100%. The higher the constant voltage is, the faster chemical components inside your battery will react, contributing to the aging process.

Thirdly, electronic experts suggested we charge our device at different times of the day instead of continuously charging until the battery is full. Many people are too busy to follow this rule, so they just charge once a day. But you just need to spend some time on this, you will see it’s effective.

2. Plug in the charger when the capacity is notified to run out:

Normally, most laptops and smartphones will have notifications when the battery goes down under 20%. You should immediately charge your device after seeing this notification. Many people continue using their batteries until it’s totally run out of capacity. This will definitely damage the battery lifespan.


In fact, to protect your battery, you had better avoid remaining it in “weak” condition for a long time. Of course, this might be difficult if you are hanging out with your friends and the battery suddenly runs out.

In that case, if your battery only has under 10% of capacity left, you should turn off the power immediately, and wait until it can be charged.

3. Turn off the device so that the charging process can be faster:

Many people, especially young generations, have a habit to use their phones while they are being charged. This will force your battery to work between “power in” and “power out” modes, extending the charging time, and more importantly, it’s not good for your battery.

Playing games or using applications during the charging process may even make your device explode since its temperature tends to highly increase.

Even if you don’t use your device and just let it there with the charger, your battery will still release some power while being charged due to several updating activities.

Therefore, you should turn off your device’s power or set it in Flight mode to limit unnecessary updates on wifi or 3G so your battery can focus on only charging.

4. Choose the right charger:

Technically, you should only use the charger that was manufactured for your device model. They are usually sold in the same box as your device. If you have used your original charger for a long time and it’s been lost or broken up, you can buy a new best 18650 battery charger that is the same or similar to the previous one.

Choose the right charger

Besides, you might be aware that sometimes your device is charged faster than usual when using a different charger. Well, this seems to be more convenient, but that’s quite harmful to your battery.

Because some chargers have a higher constant current (or constant voltage), they will be able to accelerate the charging process, but at the same time put pressure on your battery. Therefore, try to choose a suitable charger to work with your device!

5. Charge your device at a cool temperature:

Temperature is also very important in protecting batteries’ life. Whether it is too hot or too cold, it can still affect your batteries.

Research has shown that batteries used between 250C – 300C will be able to remain at 85% of their capacity after 1 year, even if you often charge it from 0% to 100% (of course the capacity will be even more if you follow the “partial charge” rule).

On the other hand, if your battery is usually put at 400C, it will only get about 65% capacity left after 1 year. If the temperature is up to 600C, your battery will quickly reduce its capacity to 65% after only 3 months.

That’s why you should always pay attention to the temperature around your electronic device. Never use it when charging or put it on your car in the sunshine, also don’t put it under your pillows to charge at night. All of those will put your battery on heat and that’s not good for a long time.

Tips to extend the life of a 18650 battery

The 18650 battery is actually a lithium-ion cell made in a standard size of 18mm x 65mm. Nowadays, it is used a lot in flashlights, laptops, and other high-tech devices because of its convenience and rechargeability.

Normally, this type of battery can be charged about 500 times. However, if you don’t use it properly, it will be broken earlier.

Below are 5 tips to extend the life of a 18650 battery:

1. Keep Your Batteries At Room Temperature:

Heat is one of the biggest factors that have a bad influence on your battery life. Normally, you should protect your 18650 batteries at a temperature between 20°C – 25°C (about 68°F – 77°F), in a dry room with moderated humidity levels.

Keep Your Batteries At Room Temperature

Especially in case, your battery is fully charged, you had better not leave it in a car parking out under the sunshine. Even when it is being charged, it also should be put at room temperature to avoid overheating.

Many R&D centers have worked really hard to find out the impact of high temperatures on your batteries. It was proved that each 8°C rise in temperature breaks the life of a sealed lead acid battery in half. For example, if your battery is expected to last 3 years at 25°C, it will only last for 1.5 years when being kept at 33°C.

And more importantly, once your battery life is damaged by heat, its capacity can’t be restored. That’s why you should always pay attention to the place you leave your device.

2. Avoid Frequent Full Discharge:

You shouldn’t wait until your battery is fully discharged to recharge it. Electronic experts recommended that a 18650 battery should be recharged right after it drops down to 40%.

The reason is that lithium-ion chemistry prefers partial discharge to deep discharge. If you discharge a lithium-ion battery below 2.5 volts, the built-in safety circuit opens to stop the flow of charge.

As a result, the battery looks like it has no charge. In this case, you can’t use the original charger. The only way is to use a battery analyzer that features the boost function to recharge the unit.

Apart from the above, you also need to remember not to recharge a deeply discharged battery after leaving it for a long time, even several months.

3. Allow Partial Discharges:

As mentioned above, lithium-ion chemistry prefers partial discharge to deep discharge. Lithium-ion batteries don’t have a charge memory, so deep discharge cycles aren’t necessary.

A lot of people usually wait until the battery goes all the way down to zero, then recharge it to 100%.

In fact, you shouldn’t do that since lithium batteries have a limited number of cycles where they can be fully charged and discharged (normally 200 – 300).

After going beyond that limit, the battery life tends to decline. Therefore, instead of charging your device up to 100% every day, you should only fully charge it once a month.

4. Never Overcharge Your Batteries:

Perhaps you have already known this because it’s one of the most popular pieces of advice that you can hear from customer service after buying a new electronic device like a laptop or smartphone.

That’s true. Excessive charging can bring on thermal runaway in a lithium battery. Technically, lithium-ion work well within the designated operating voltages. However, it would become unstable if charged to a higher voltage.

Li-ion cannot absorb overcharge. When fully charged, the charge current must be cut off. If you keep charging continuously after that, it would lead to plating of metallic lithium and compromise safety.

In fact, a 18650 or lithium-ion battery is not the only type of battery being negatively affected by overcharging. Lead- and nickel-based batteries are also known to melt down and cause a fire if improperly handled. Therefore, you must be really careful whenever charging your device.

5. Store In A Cool Place At 40% Charge:

Not many people are doing this, but storing 18650 batteries at lower temperatures will slow their self-discharge rate dramatically. Many people even said that you could put the batteries in your fridge. But you shouldn’t really do that. You only need to keep it in a cool, dry, and non-refrigerated location.

Normally, a battery should be fully charged before being used so that it could be in the best condition.

However, it would be harmful to your batteries before storage. The best battery manufacturer usually stores lithium-ion batteries at a 40% charge. This would allow a stable condition even in terms of a level of self-discharge.

In this case, a certain reserve charge is necessary to keep a battery and its protection circuit operational during long periods of storage.

In short

That’s all for the top 5 tips to extend the life of your 18650 batteries. If you remember and follow these tips, the lifespan of the 18650 battery of it would be extended and you can use them longer than expected.

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