The Vape Store Blog

Charging your batteries – USB or external battery charger, which is safer?

If your device takes 18650 batteries, is it safer to charge them while they’re in the device, or remove them and charge in an external charger? Let’s take a look.

How should you charge your battery? That’s actually a very good question when you first start vaping – battery safety is one thing all vapers should learn. It becomes even more important as you gradually make your way up to the more powerful devices on the market. Then, devices like Efest and Nitecore battery charger┬ábecome your best friends.


Starter Kits

Eleaf iStick BasicMany devices only have one option – on-board charging with a Micro USB cable. Starter kits like the Innokin Endura T18, Aspire Breeze AIO and Eleaf iStick Basic all contain an internal lithium-ion battery – much like the one in your mobile phone – which must be charged within the device.

These devices all have internal safety mechanisms which prevent the batteries from encountering any problems while charging. Since they require less power to run, they are able to use smaller batteries in order to maintain a long charge. During charging, the smaller internal battery and the lower charging speed from a Micro USB cable both help to keep the device cool and safe.

These devices usually charge at about 500mAh, or 0.5 Amps per hour. A 650mAh battery on the Breeze, for example, would then charge in about an hour-and-a-quarter. A 1000mAh Endura T18 would charge in two hours. These are relatively quick for the device in question. Depending on the AC adapter and cable in use – and if the devices themselves allow faster charging – they can sometimes be charged at 1A or even 2A.

Charging internally via Micro USB is perfectly safe in vape devices that present only this option, such as the Endura T18 and iStick Basic. Click To Tweet


Devices with external batteries

When we say “external batteries” we are typically talking about any device that uses 18650 batteries, 26650 batteries, 20700 batteries or 21700 batteries which are removable. These devices take between one and four of these batteries (in extreme circumstances they can take more). The batteries are accessible via either a door which flips open or a plate which pulls off, and they must be inserted in the correct order and polarity (+/-) to work.

Like the internal batteries used in starter kits, these are usually lithium-ion (Li-ion) batteries, but can also be lithium-ion polymer (LiPo). They are effectively the same battery technology, but sometimes need to be cared for in a very different way.

Until late-2015, no vape devices with multiple external batteries were able to be charged on-board. Mods like the Sigelei 100W and Cloupor T8 150W both took two 18650 batteries, and those batteries needed to be removed and placed into an external charger when they were low.

This changed with the release of devices like the Smok Alien 220W and the Wismec Predator. These devices had on-board balance charging, which meant that both 18650 batteries charged equally when charged via Micro USB cable. Finally, it was “safe” to charge a multi-battery device internally.


It’s safe, but it’s still safer to charge externally

There are some major differences between charging the same two batteries on-board versus in an external charger.

Speed is one of the major differences. In a dual 18650 mod running two Samsung 25R batteries, you’re charging a total of 5000mAh. If you’re charging internally, even at 2A it’ll take two-and-a-half hours in theory. However, since AC adapters must compensate for charging multiple batteries at the same time, the math can get a little convoluted. A dual battery mod will actually charge at 1.07A out of the wall.

Taking those batteries out and placing them into an external charger has a significant advantage when it comes to speed. Both batteries will make use of an overall faster available power output.

In the four-bay Efest LUC V4, for example, the maximum available output is 4A and this is spread among as many batteries as you choose to charge. Charging four batteries can be done at 1A, or charging two batteries can be done at 2A. That’s twice as fast as in the device.

The charge goes separately into each slot on the external charger, and each battery’s information is read separately. It is therefore evident that batteries charged in an external charger are far more likely to be charged equally and at the same rate.

Comparison of Micro USB and Nitecore charging boards

Since the Efest or Nitecore charger has one job – to charge – almost the entire internal mechanics of the device are essentially one big charging board. Vaping devices, meanwhile, have many jobs and charging is just one of them. The charging board is much smaller.

In fact, an average Nitecore charging board measures approximately 60mm by 45mm; an average Micro USB charging board measures 25mm by 19mm, or actually less than 1/6th the size.

Obviously, a dedicated charger with extra protections is going to perform better than a charger added as a feature within a multi-purpose electronic device.

Ventilation of heat is always going to be more effective in an open-air external charger than in a closed mod, even if that mod features excellent battery holes for airflow. Click To Tweet

Finally, ventilation of heat is always going to be more effective in an open-air external charger than in a closed mod, even if that mod features excellent battery holes for airflow. As batteries typically heat up as they’re charged, putting two or three of them side-by-side, often touching, in an enclosed space isn’t the best idea.

For these three reasons – speed, accuracy and heat dissipation – The Vape Store always recommends that users of high-powered, multi-battery devices seek out an external battery charger at their earliest opportunity. Budget conscious buyers will naturally be drawn to devices which feature on-board charging, but should always prioritise battery safety when they get a chance.


Are all external chargers built the same?

Mostly, yes, they’ll all do the same job. Some have LED screens which will indicate the charge of each separate battery individually, and some have the ability to alter the output and charge speed. Others even have Bluetooth and can be linked to an app on your smartphone.

Generally, we recommend reputable brands such as Efest and Nitecore, who both make great external chargers. Most of these chargers support charging of 18650, 26650, 20700 and 21700 batteries, as well as more obscure sizes (13500, 16500, 18350, 18500, and many more). Most of them also do standard battery sizes (AA, AAA, C and D) without any issues, too.

Some of the better chargers on the market include the Nitecore Digicharger D2 and Nitecore Digicharger D4, Nitecore Intellicharger I2 and Nitecore Intellicharger I4, Efest LUC V4 and Efest LUC V6, Efest LUSH Q2 and Efest LUSH Q4, and even the single-bay USB-powered Efest LUC Mini.

Damien Heath

Damien Heath


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