How much time it takes to charge a solar power bank?

Posted by ifihomes on 7th Jun 2016

How much time it takes to charge a solar power bank?

Every solar enthusiast always wonders on how much cost saving he anticipates and what is the ROI (return on investment) when he plans to buy a solar product

When it comes to the case of solar power bank, the biggest question is –

How much time it takes to charge the power bank??

Answer is very simple and yet can be made very complicated (if you want to get into nitty gritty of solar power and conversions and losses)

Let’s start from start with a basic primer on electricity. While this info doesn’t go into the intricacies of charging curves or the subtleties of solar charge controllers and voltage regulators, just providing you with enough information to make more informed buying decisions.

Voltage, Electricity, Wattage? If you are familiar with this skip next three paragraphs

Volts (V) measure the amount of electrical potential in system. Volts would be the equivalent of the water pressure in house plumbing. The higher the pressure, the more power is ready to go when you turn on the tap. In India power is supplied at 220 V, car battery is 12 V, and anything drawing power from a USB port is 5 V.

Amps (A) measure the amount of current in system and also most used term. General plugs are 9A and A/Cs and big power guzzling devices are connected to 15A. Smart phones draws around 1A & tablet probably draws around 2 A to 2.5. Ex: wider the water pipe more the water flow. Solar chargers to handle charging a tablet or battery pack more quickly, current requirement is to accommodate 2 A.

Watts (W) are probably the most frequently mentioned unit of power. In the electrical world, volts multiplied by amps is equal watts. If you want to understand it with water flow example, watts would be the amount of water passing through your shower/tap head in a split second. If you have high water pressure (volts) and a really big pipe (amps) then you’ll have great water flow (watts).

It also means that if you know any two of these numbers, you can figure out the third. Your 1,200-W microwave, running off of household 110-V power, would be using 10.9 A because 10.9 A x 110 V = 1,200 W

What a regular tab/pad battery voltage and ampere requirements?

          5V and 2A

What a regular smart phone battery voltage and ampere requirements?

          5V and 1A

What a solar power bank contains, what is its capacity, what is the wattage of the solar panel?

           Batteries and gadgets we test with are generally measured in amp-hours (Ah) or milliamp-hours (mAh). 1 Ah = 1,000 mAh. Simplified, this means that if you plug in your phone for an hour, and it draws 1 amp the whole time, it will have charged up 1 Ah, or 1,000 mAh. If the current is low for some reason, and the phone can’t draw more than 0.5 A, then one hour will only get you 500 mAh. For comparison, the iPhone 6 battery has a 1,810-mAh capacity, while the Galaxy S5 has a 2,800-mAh battery.

      With this knowledge, it’s easier to understand the relationship between solar chargers and your favourite gadget. Since most gadgets today charge off of USB, the voltage is pretty much fixed at 5 V. Depending on the gadget and battery, the manufacturer has a certain amount of amps needed to get a healthy charge in a reasonable amount of time, but not so much that it sustains damage. Your smartphone probably draws about 1 A and your tablet about 2 A. So a smartphone draws 5 V x 1 A = 5W and your tablet draws 5 V x 2 A = 10 W.

Time taken to charge = (Power bank capacity) / (power generated by panel) =

Let us take an example of solar power bank that claim it has a 2W panel, it will produce electricity of 400 mAh at 5V, will conversion losses and weather conditions, we can give a factor of safety of 20-25% losses. Let us assume a 300 mAh. If you have a power bank of 3000 mAh then it would take

             Ex: 3000 / 300 = 10 Hours of charging in the sun

So while most portable solar banks available today use panels that generate somewhere between 2 W and 4 W. The bigger the battery of solar power bank it will take more time to charge, conclusion is solar power banks are best alternative source of power in absence of regular power source. It can’t be sole source of power unless you are willing leave the power bank outside for 2-3 days.

What are the Alternatives for Solar Mobile Chargers?


How much time these solar mobile chargers do take to charge a smart phone (Ideal Conditions)

Better alternate is to club any regular power bank with bigger flexible panels that can produce 10W -15W, the more power it can create in a given amount of surface area. Going higher than 20 W will cost you more money and give you more power than you can really use if you just want to charge one or two devices. This is the best alternative to use solar charge and also have the needed power in the power bank

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