A Powerbank is a portable battery backup device that is designed to supply electrical power to charge small electrical devices. These include smartphones, wireless Bluetooth speakers, LED lights etc. There are Powerbanks that are even capable of charging laptops these days.
There are so many misconceptions and
myths about powerbanks that this author can spend a whole day debunking. But we do not have all day.
How do powerbanks work?
A powerbank is essentially a battery
with a circuit board that is designed to charge other devices. Every good
powerbank should have a circuit board with a chip that can intelligently monitor
the battery, ensure safe charging and modify or cut off power supply if need be.
Every powerbank that uses wired charging conforms to the USB 5V standard. The batteries inside a powerbank have a standard voltage of 3.7V. When a device is plugged to a powerbank, the current is stepped up from 3.7V to 4.2V – 5V. This stepped up current is then delivered to the device being charged.
Read: Smartphone chargers
Due to this conversion of battery
voltage from 3.7V to 5V, a good amount of electrical power is lost, mostly as heat. As a result, powerbanks cannot deliver their full advertised capacity.
Powerbank manufacturers advertise the
capacity of their batteries when it is stored at 3.7V. When checking a powerbank’s capacity, it could be written as 30,000mAh at 3.7V or 18,000mAh at 5V.
When 3.7V is converted to between 4.2 – 5V, the amount of current that the powerbank can deliver falls drastically. There is a very simple formula to convert this.
Actual capacity = Advertised capacity
(mAh) x 3.7V x 0.8 ÷ 4.2V
For a 20,000mAh
Actual capacity = 20,000 x 3.7 x 0.8 ÷ 4.2V
= 59200 ÷ 4.2
Actual capacity = 14,000mAh approx.
If you cannot remember this formula,
then always remember this. A powerbank can only deliver approximately two-thirds (2/3) of the advertised capacity. This means that a 5,000mAh would deliver approximately (5,000 x 2/3=) 3,400mAh. A 10,000mAh would give approximately (10,000 x 2/3 =) 6,700mAh. A 30,000mAh can give out 20,000mAh approximately.
How much charge can a powerbank actually give
Now that we have seen how powerbank
capacity is being calculated, how much charge a powerbank gives out, especially
to a phone is not an exact science. If a phone is used while being charged, work
done could be equal to zero. If the phone was left alone or even switched off, then the powerbank would accurately charge its battery properly. The age of the powerbank and its charge capacity is also another factor to look at. Powerbanks tend to lose capacity as they age. A 2 year old, 20,000mAh powerbank may only have 10,000mAh left.
Read: How to charge your phone
Do powerbanks destroy phone
Yes and no. A good powerbank has no
negative effect on your battery. It should come with a good circuit board to
ensure safe and quality charging. A bad powerbank on the other hand would
destroy your battery. This is why it is important to buy powerbanks from
reputable brands instead of cheap generic brands from roadside vendors.
How to choose a good powerbank
The first step is to always do research. A lot of people are too lazy these days to do research. Read reviews and learn to distinguish between real and paid reviews. Manufacturer’s brand name and reputation matter a lot here as well. Names like Anker, Aukey, Romoss, Xiaomi etc. should come to mind.
Check the powerbank’s specs (input,
output, capacity etc.) as well. If a spec looks too good to be true, it
probably is. Someone once showed me a 100,000mAh powerbank. I laughed it off
and said it was a scam. The bigger the capacity, the heavier the powerbank.
Always do your research before splashing your cash.
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