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How do you know when your portable charger is fully charged?

Portable chargers or power banks have small LED light indicators that give information about the various states of the unit. Decoding the information provided by these indicators is very helpful in safely and correctly using the power bank.

The power bank LED indicator lights and their functions

Some power banks have 4 small blue LED indicator lights. When you connect your power bank to a power outlet to load it, one of the LED lights will blink, indicating that the power bank is taking up the charge.

While connected to the power source, the power bank’s LEDs indicate the charge taken up by the power bank until then:

fully charged power bank

  • 1st light blinking means it is charged between 0%-25% and charging
  • 2nd light blinking means it s charged between 25%-50% and charging
  • 3rd light blinking means it is charged between 50%-75% and charging
  • 4th light blinking means it is charged between 75-100%. And charging

When all 4 LEDs stay steadily lit, it means that the power bank is fully charged and should be immediately disconnected from the power source. Power banks have built-in battery protection systems to prevent overcharging and overheating. Still, it is advisable not to leave the power bank connected to the power source for a long time after it is fully charged, as it may damage it.

In case all 4 LEDs start blinking, it indicates that the unit has developed some fault. In this case, it’s advisable that the device should be looked at by a professional

 repairman, or if it’s still under warranty, it should be sent back to the vendor for repairs or replacement.

Here is the same information in a table format:

portable charger LED status

When the power bank is disconnected from the power outlet, none of its LEDs will be lit. To check the charge level of the power bank, press the check button. On most power banks this button is located on the side. On pressing the button once, you will see 1, 2, 3 or all 4 LED lights glowing steadily.

  • 4 LEDs lit means the power bank is fully charged
  • 3 LEDs lit mean the power bank is 75%-50% charged
  • 2 LEDs lit means the power bank is 50% to 25% charged
  • 1 LED lit means the power bank is 5% to 25% charged
  • No LED lit means the power bank is totally discharged

How to check the charge on power banks with two indicator LEDs.

Some power banks have two LED indicator lights, normally a blue and a red LED. In this case, the LEDs indicate the following:

  • Steady blue light – The power bank is charging the mobile device.
  • Flashing blue light – The power bank needs to be charged
  • Flashing red light – The power bank is being charged from a power source
  • Steady red light – The power bank is fully charged

Please refer to the specific user manual of your power bank to understand the correct interpretation of the LED lights.

How to check the charge on power banks with no indicator LEDs?

Very low-cost power banks have no LED indicator lights at all. In this case, you have to read the manual and find the time it takes to fully charge it. You can also calculate the charging time yourself.

How can you calculate the charging time?

Battery LifeFirst, find out the charge capacity of your power bank. This is usually written on the power bank and if not, certainly in the accompanying manual. This will be in units of mAh which is short of milliampere-hours. Next, find out how much current can be delivered by the power source in Amperes, which is written on the power charger.

Say your power bank has a capacity of 10000mAh and the power charger can deliver a current of 2 Amperes. 1000 mA = 1 Ampere and ‘h’ is the time in hours.

Then time to full charge will be 10000mAh/2A= 10 Ah/2A = 5 hours.

This calculation assumes 100% efficiency, which is not accurate in real-life situations. Most power banks have efficiencies ranging from 60% to 80% due to energy losses during charging and discharging. For more realistic results use 7500mAh instead of 10000mAh. Read more about the real capacity of your power bank.

Another thing to take into consideration is that power banks have their charge-holding capacities reduced over time with heavy usage. You will see a marked difference in the charge-holding capacity of your power bank after it has undergone 100 to 500 charge/discharge cycles, depending on the brand and its quality.s

In most cases, 500 charge cycles in a power bank can result in about 20% loss of its charge holding capacity, while cheaper ones won’t last even 100 cycles. Charge holding capacity also decreases over time.

It may also decrease, if the power bank is subjected to high temperatures, like being left in the car on a hot day. You can re-calculate the charging time of your power bank using the above formula with reduced charge holding capacity.

How do you know when the power bank is fully charged if the LED indicator lights are not working at all?

The easiest way to know if the power bank is working or not, while its LED indicators have failed, is to simply test it. Load it with charge and then try to charge a mobile device. If it is charging the mobile device then your power bank is working fine.

If you are technically adept, then you can know the state of charge of your power bank by measuring the terminal voltage of the batteries with a voltmeter. The common type of power banks use 18650 type lithium-ion batteries and at full charge, their terminal voltage should read 4.2 volts. Please only do this if you are knowledgeable about electronics to avoid any potential safety risks.

How to avoid damaging your power bank?

You should not over-charge your power bank and also not completely discharge it. If you do so frequently, then in both cases the life of the power bank will decrease swiftly. If you leave your power bank for a long time without using it, it will slowly discharge beyond the critical level and may be damaged.

It is advisable to charge your power bank every couple of months or so, even if you are not using it. Avoid leaving or storing your power bank in a very hot or very humid environment.

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