The basic steps: plug, wait, unplug

Charge your portable charger the same way you charge your phone — plug the charger into a wall outlet using its included cable, and leave it connected until the indicator light shows it is full. Most portable chargers take between two and eight hours to charge completely, depending on their size and the power of the outlet you use. A standard USB outlet (5 watts) charges slower than a wall adapter rated for 18 watts or higher.

Check the indicator light on your charger. A solid green light usually means fully charged; a blinking light means it is still charging. Some chargers have a small screen that shows the percentage. Once it reaches 100 percent, unplug it from the wall. Leaving it plugged in after it is full does not damage modern chargers, but unplugging it saves a small amount of electricity.

Key Takeaways

  • Use the cable and power adapter that came with your charger, or a certified replacement, to avoid damage to the battery.
  • Charge your portable charger from a wall outlet, not from your phone or computer, because wall outlets deliver power much faster.
  • Most portable chargers last longest if you avoid letting them sit completely empty or stay plugged in for weeks without use.
  • The first charge does not need to be longer than any other charge — the myth of a 12-hour first charge is outdated.

Which cable and power adapter to use

Use the cable and power adapter that came in the box with your charger. If you have lost them, buy a replacement from the charger's manufacturer or look for a certified third-party cable marked with the USB-IF logo (a certification from the USB standards organization). Uncertified cables can deliver the wrong amount of power and damage the battery inside your charger.

The power adapter matters more than most people realize. A 5-watt adapter (the kind that came with older iPhones) will charge your portable charger, but slowly. If your charger supports fast charging, use an adapter rated for at least 18 watts. Check the back of your charger or the manual to see what wattage it accepts. Using a higher-wattage adapter than recommended can overheat the battery, so do not guess — look it up.

Charging from a wall outlet versus other sources

Always charge your portable charger from a wall outlet, not from your phone or computer. A wall outlet delivers steady power at a consistent voltage. Your phone or computer delivers power unevenly and at lower speeds, which means your charger will take much longer to fill and may not charge completely. Charging from a computer also drains your computer's battery if it is a laptop.

Wall outlets are also safer. Charging through a phone or computer adds an extra step where the power passes through another device's circuitry, which increases the small risk of a power surge damaging your charger. A direct wall connection bypasses that risk.

How often to charge and when to store it

Charge your portable charger whenever it drops below 50 percent, or whenever you know you will need it soon. You do not have to wait until it is completely empty. In fact, letting a lithium battery (the kind inside most portable chargers) sit at zero percent for weeks can permanently reduce how much charge it holds. If you use your charger regularly, charge it once a week or whenever it runs low.

If you are storing your charger for months without using it, charge it to about 50 percent before you put it away. Store it in a cool, dry place — not in a hot car, a damp basement, or direct sunlight. Check on it every few months and top it up to 50 percent if it has dropped below 20 percent. This keeps the battery healthy during long storage.

Why your charger might charge slowly

A slow charge usually means one of three things: the power adapter is too weak, the cable is damaged, or the outlet itself is not delivering full power. Start by trying a different outlet in another room. If the charger charges faster there, the original outlet may be faulty or overloaded.

Next, try the original cable and adapter that came with your charger. If you have been using a different cable, switch back. A frayed, bent, or old cable can restrict power flow. If the original cable is damaged, replace it with a certified one from the manufacturer. If you are using a weak power adapter (5 watts), upgrade to an 18-watt or higher adapter if your charger supports it.

Temperature and safety while charging

Your portable charger should feel slightly warm while charging, but not hot. If it becomes too hot to touch, unplug it when ready and let it cool for at least 30 minutes before trying again. Excessive heat damages the battery and can be a sign of a defective charger.

Charge your charger in a well-ventilated space, not under a pillow or blanket. Do not charge it while it is inside a bag or case that traps heat. If your charger gets very hot repeatedly, or if the indicator light flickers or turns off unexpectedly, stop using it and contact the manufacturer. A charger that overheats or behaves erratically may have an internal fault.

The first charge myth

You may have heard that you should charge a new portable charger for 12 hours before using it. This information was true for older nickel-cadmium batteries from the 1990s, but modern lithium batteries do not need it. Charge your new portable charger the same way you charge any other charger — plug it in until the light shows it is full, then unplug it. A normal charge cycle is all it needs.

The only exception is if your charger arrived completely empty and you want to make sure it is truly full before you rely on it. In that case, charge it for the time listed in the manual (usually two to four hours), then unplug it. You do not need to wait longer.

Frequently Asked Questions

Can I charge my portable charger while I am using it to charge my phone?

Yes, but it will charge both devices more slowly. The charger is splitting its power between filling its own battery and powering your phone. If you need your phone charged quickly, charge the portable charger first, then use it to charge your phone. If you need both charged at the same time, plug both into wall outlets separately.

Is it bad to leave my portable charger plugged in overnight?

Modern chargers have built-in protection that stops charging once the battery is full, so leaving it plugged in overnight will not damage it. However, unplugging it after it reaches 100 percent saves a small amount of electricity and is a good habit to form.

Why does my portable charger charge faster some days than others?

The outlet you use, the temperature of the room, and how many other devices are plugged into the same outlet all affect charging speed. A warm room, a weak outlet, or a shared circuit will slow things down. Try charging in a cool room using a dedicated outlet with no other devices plugged in nearby.

What should I do if my charger will not charge at all?

Try a different outlet and a different cable first. If it still will not charge, try holding the power button for 10 seconds — some chargers have a reset function. If none of that works, the battery may be dead or the charger may be faulty. Contact the manufacturer for a replacement.

Can I use a fast charger on my portable charger?

Only if your portable charger is rated for fast charging. Check the manual or the back of the charger for the maximum wattage it accepts. If it says 18W or higher, a fast charger is safe. If it says 5W only, use a standard 5-watt adapter to avoid overheating the battery.