The basic method: plug it in, wait, and you're done
A power bank charges the same way your phone does — you plug a USB cable into the power bank's charging port, connect the other end to a wall outlet (or computer), and leave it alone until the indicator lights show it's full. Most power banks take between two and eight hours to charge completely, depending on their size and the charger you use. The larger the power bank's capacity, measured in milliamp-hours (mAh), the longer it takes.
The key difference from charging your phone is that you're charging a battery that will later charge your phone, so you need to think about when to do it. Unlike your phone, which you probably charge every night, a power bank sits unused most of the time. This means you can charge it whenever it's convenient — you don't have to wait until it's completely empty, and you don't have to charge it every single day.
Key Takeaways
- Plug the power bank into a wall outlet using its charging cable, and the indicator lights will show when it's full — usually in two to eight hours depending on size.
- Use the charger that came with the power bank if possible, because mismatched chargers can charge slowly or damage the battery over time.
- Charge your power bank when it drops to 20 percent, not when it's completely dead, to extend how long the battery lasts before it needs replacement.
- A power bank left uncharged for months may not turn on at all, so charge it at least once every three months even if you're not using it.
- If your power bank won't charge, try a different cable first, then a different outlet, before assuming the power bank itself is broken.
Which charger to use and why it matters
The charger that came in the box with your power bank is the safest choice. It's designed for that specific battery and charges at the right speed — fast enough to be practical, but not so fast that it damages the battery's lifespan. If you've lost that charger, look for the power bank's model number (usually printed on the back or bottom) and search for a replacement online, or ask the manufacturer what charger they recommend.
You can charge most modern power banks with any USB charger you have lying around — a phone charger, a laptop charger, or even a car charger — as long as the cable fits the port. However, using a charger with much higher wattage than the original can shorten the battery's life. A charger rated for 5 watts is fine; a charger rated for 65 watts may charge faster but will wear out the battery sooner. If you're not sure what your charger is rated for, check the label on the charger itself or the box it came in.
How to know when your power bank is fully charged
Most power banks have LED indicator lights on the front or side that show the charge level. When you first plug it in, one or more lights will turn on. As the battery fills, more lights illuminate. When all the lights are on and steady (not blinking), the power bank is full. Some power banks beep or the lights stop blinking when charging is complete.
A few power banks have a small screen instead of lights, which displays the percentage directly. If your power bank has neither lights nor a screen, you can press the power button once — it will usually light up to show the current charge level. Leave it plugged in for a few more minutes after it appears full, just to be sure.
Don't leave a power bank plugged in for days after it's full. Most modern power banks have protection circuits that prevent overcharging, but leaving it plugged in constantly can still wear out the battery faster than it needs to.
When to charge your power bank for the longest battery life
Charge your power bank when it drops to around 20 percent, not when it's completely empty. This habit extends the total lifespan of the battery by years. Lithium batteries — which power banks use — wear out faster if you regularly drain them all the way to zero. Think of it like this: a battery that goes from 100 percent to zero every single time will need replacement sooner than one that usually stays between 20 and 100 percent.
If you use your power bank regularly, charge it once a week or whenever it drops below 20 percent. If you rarely use it, charge it at least once every three months. A power bank that sits uncharged for six months or longer may lose the ability to hold a charge, or may not turn on at all when you finally need it. Set a phone reminder if you tend to forget — "Charge power bank" on the first of each month takes thirty seconds and keeps the battery healthy.
Troubleshooting when your power bank won't charge
If you plug in your power bank and nothing happens — no lights, no sound, no sign of life — start with the cable. Try a different USB cable first, because a damaged cable is the most common reason a power bank appears broken. If a different cable works, you've found the problem and can replace the cable. If it still doesn't work, try plugging the power bank into a different wall outlet, because the outlet itself might be dead.
If the power bank still won't charge after trying two different cables and two different outlets, the battery or charging circuit inside may be damaged. At that point, contact the manufacturer with your model number and purchase date — many offer warranty replacements if the power bank is less than a year old. Do not try to open the power bank or charge it in an unusual way, because lithium batteries can be dangerous if damaged.
One more thing: if your power bank has been sitting unused for many months, it may take several minutes of charging before any lights appear. Plug it in and wait five minutes before assuming it's broken.
Charging your power bank while you're using it
You can charge a power bank while it's charging your phone at the same time, but it will charge both devices more slowly. The power bank has to split its incoming power between charging itself and powering your phone, so the process takes longer overall. If you're in a hurry, charge the power bank alone first until it's full, then use it to charge your phone.
Some power banks have two USB ports — one for charging the power bank itself, and one or more for charging your devices. If yours has this setup, you can plug the power bank into a wall outlet and your phone into the power bank's output port at the same time, and both will charge. Check your power bank's manual or the labels on the ports to see which port is for input (charging the power bank) and which is for output (charging your devices).
Frequently Asked Questions
Can I charge my power bank with a fast charger?
Yes, but it may wear out the battery faster than using the original charger. A standard 5-watt charger is safest. If you use a fast charger rated 18 watts or higher, the power bank will charge quicker but the battery won't last as many years before it needs replacement. Check your power bank's manual to see if the manufacturer lists a maximum wattage.
What if my power bank gets hot while charging?
Mild warmth is normal, but if it's too hot to touch comfortably, unplug it when ready. Excessive heat means the charger or battery may be damaged. Try a different cable and outlet. If it still gets very hot, stop using it and contact the manufacturer — a damaged battery can be a safety risk.
How long does a power bank battery last before it stops working?
Most power banks last two to three years of regular use before the battery degrades noticeably. After that, it will still charge and hold some power, but not as much as when it was new. If you charge it properly — not letting it sit empty for months — it will last toward the longer end of that range.
Can I leave my power bank plugged in overnight?
It's not ideal, but most modern power banks have built-in protection that stops charging once the battery is full. Doing it occasionally won't cause when ready damage, but regularly leaving it plugged in for hours after it's full will shorten the battery's lifespan. Unplug it when the lights show it's full.
Why won't my power bank turn on even though I charged it?
Try pressing and holding the power button for three to five seconds — some power banks require a longer press to turn on. If that doesn't work, try charging it again for at least an hour, because a completely drained battery sometimes needs time to "wake up." If it still won't respond, the battery may be damaged and you may need a replacement.