How Long Does it Take to Charge an 18650 Battery? 

Charging 18650 batteries for the first time

Most battery manufacturers typically ship their cells at approximately 30% charge to maintain the health of the batteries while they are in storage awaiting purchase. When you first plug in your batteries, it will generally only take a few hours to reach full charge.

Daily Charging

The time required to recharge your batteries on a daily basis may be slightly longer than the initial charge, and it depends on several factors. The battery’s capacity, measured in milliamp Hours (mAh), is the most significant factor. A higher battery capacity means a longer charging time.

The type of charger you use is also important to consider. If you’re using an external charger, you should check its specifications to determine the amount of power it’s supplying to your batteries. If your device has a built-in USB charger, you may be able to use the quick charge feature. Each approach has its own set of advantages and disadvantages.

Samsung 30Q 3000mAh 18650 15A Rechargeable Battery
A Samsung 30Q 18650 cell

Battery Chargers

For maximum battery life span, it’s best to charge them slowly and consistently at around 0.5 amps. If you’re using a multi-bay charger with two, three, or four batteries, keep in mind that the amperage applied to the batteries may vary based on how many you have plugged in. When all four batteries are connected, they will all charge at 0.5A. However, when only two batteries are plugged in, they will charge at 1A, effectively halving the charging time but potentially shortening the battery’s lifespan.

This is because rapid charging causes the battery to heat up, which can damage its internal structures. Even once the charger indicators show that the battery is fully charged, you may notice that it holds less and less charge over time. To avoid having to replace your batteries frequently, it’s best to always charge them at the slower 0.5A rate.

How to charge 18650 Battery with USB?

To charge your 18650 batteries via USB, you’ll want a charger that has a 5V USB power source. Fortunately there are many chargers from top brands such as Nitecore which allow convenient charging from any location.

Top chargers include the Nitecore D2 USB charger and the Nitecore Ci4 4 Bay Battery Charger. These chargers can be plugged in to any USB port on devices such as a laptop or power bank.

Nitecore UMS4 4 Bay LCD Battery Charger
A 4 Bay Battery Charger

18650 Battery Charging Safety

To ensure the safe use of Lithium-Ion batteries, it is important to use a charger specifically designed for these batteries. It is also recommended to avoid leaving the battery charging unattended and to remove it from the charger once the charging cycle is complete. Although rare, charger failures can occur, so it is best to charge your batteries when you are present and able to monitor them. Once fully charged, remember to disconnect the charger from the power source.

Top 18650 Battery Charging Safety Tips

  1. Always keep your batteries in a case when not in use.
  2. Do not store your batteries in direct sunlight.
  3. Keep batteries away from flammable objects and materials.
  4. Never leave a battery unattended whilst charging.
  5. Keep batteries away from static electric charges.
  6. Keep out of reach from animals and children.
  7. If a battery has a damaged wrap, it should be repaired or disposed of immediately.
  8. Do not crush, incinerate or modify your batteries.
  9. Only use batteries within the manufacturers specifications.
  10. Recycle your batteries correctly – never throw them in the bin.

3 thoughts on “How Long Does it Take to Charge an 18650 Battery? ”

  1. After 10 years of use, I have noted that my intellicharger i2 predictably charges my IMR18650s at a rate of 1hr / 500mAh capacity. That is; a 2000mAh battery charges in 4 hrs vs. a little over 5 hrs for a 2600 mAh battery. Any longer usually means that it’s time to clean the charger’s contacts or the batteries themselves. Can anyone confirm the charge rate with 21700s?

  2. Im charging my 18650 battery direct from 24 V socket how long should i charge my battery

    • Hi Mohammed, The correct charging voltage for an 18650 battery is between 4.2V and 4.4v. It’s not safe to use 24V, even if it looks like its working, it will be damaging your cell. We recommend you purchase a dedicated charger


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