Ads have started popping up everywhere online for so called "30000mah solar powered battery banks". Some of these powerbanks sellers even went further to claim they had powerbanks with 50000mah worth of charge.. Even 80000mah. To make the offer even sweeter manufacturers of these powerbanks have added "solar charging" to the mix. All this tech is combined with prices so low make the devices sound like manna from heaven. This post will investigate some of the claims of said powerbanks to see how true these numbers really are..
Almost all rechargeable batteries used in powerbanks are lithium batteries .
The unspoken truth about powerbanks and mobile batteries (especially lithium) in general is that the tech has started reach a plateau in terms of size to charge capacity in the past few years. As such, you can roughly estimate the capacity of a lithium battery just by looking at its size. Given this moderate assumption it's about right to say a 30000mah battery fitted in a power bank should be 10 times as large as your typical phone battery. However most of the powerbanks we see today claiming to hold up to 30000mAh of charge are small enough to fit in your pocket. In reality, a battery of that capacity should look at least 3 to 4 times as large as a moderately sized phone
Before you buy a powerbank always ask yourself . "Is the rated capacity of this powerbank realistic?"
Now let's open a typical 30000mah solar power bank sold in Nigeria to see the true capacity of the battery inside.
As you can see from the images above, the powerbank contains just two 2400mah batteries for a combined capacity of 4800mah. Not the 30000mah advertised. The true capacity has been inflated more than 6 times over. For a little perspective, let me tell you the capacity of the typical single AA battery.. 2400mAh ! .This so called 30000mah has no more capacity than two regular finger batteries you can buy from any store.
By now I guess some of you are thinking. "Well, it has solar charging so even if the capacity isn't large enough I can just harness my free sunlight to keep my phone charged 24/7"
As to whether the solar panel charges the batteries at all, I cannot confirm. You do see a set of LEDs on the side of this particular powerbank light up when the solar panel is under direct sunlight.. So you are thinking..."something must be charging right?"
For the science inclined, let's do a little rough calculation here to see why a solar panel that small is basically a waste of time (you can skip if you just want the results)
The best solar panels you can buy will provide 230 watts of power per square metre under direct sunlight
See more on solar panel efficiency here: http://www.solarpowerrocks.com/solar-basics/how-much-electricity-does-a-solar-panel-produce/
Being very generous, the size of the solar panel on top of this power bank is 7.5cm by 15cm. Multiplying this you get an area of 112.5 square cm. Convert that to square metres and you get 0.01125 Sq metres
Multiplying the area of the powerbanks solar panel by the "premium" power output of 230Watts per square metre; The power output of the powerbanks solar panel is 2.6watts
The standard charging voltage for lithium batteries is 5 volts.. Using the power, voltage, current relationship:
Power= current x voltage
2.6watts=current x 5 volts
Current = 0.52A
Current = 520mA
So charging current from the solar panel (after converting from solar panel voltage to 5v) to the battery is 520mA.
NOT 1A or 1000mA (solar) as stated on the back of the powerbank below
To charge 30000mah:
30000mAh/520mA= 57 hours of full blast sunlight
To charge 4800mAh:
4800mAh/520mA= 9 hours of full blast sunlight
And this is all assuming you have world class solar panels attached to your cheap off the counter powerbank! In reality, you might have to double your charging time for regular grade solar panels of this size
Long and short, factoring in sunlight availability and electrical losses, you probably will not be able to charge this powerbank by solar electricity. In fact the LED charging lights will probably suck all the current produced by the solar panel just to indicate that it is charging.
Before you buy any powerbanks please ensure you have a good grasp of the content of what you are buying.
Buy from reputable brand names and don't fall for this solar charging gimmick. It doesn't work well enough to be viable.
There are larger portable panels that do work, however they are difficult to come by in Nigeria.
Please share with friends so they don't get sucked into the same gimmick.