DIY iPhone Solar Charger

[butt]

While looking around on youtube, I saw someones post on a solar powered phone charger. Thought it was a pretty cool idea. Having zero understanding on anything electrical (and I mean ZERO) took it as a personal challenge to learn something new!

Here is guy on youtube that made one:



Then I went to ebay and saw you could buy something similar for under $20. Kinda burst my bubble a little... Then reading the fine print on these things, sounds like someone would need 12-16 hours of sunlight, just to charge an iphone. Well, that dog dont hunt. So now wanting to learn something on a slightly larger scale. Think something that could charge up a few ipads/devices each day has a more practical energy production goal.

Here is a larger kit someone got from Harbor Frieght
https://www.youtube.com/watch?v=eYlJcC0wT8E&feature=youtu.be

Think something that is between the two above ideas would probably work? Someone mentioned these things are big with RV/campers and boaters, so will see if I can find more info. Anybody ever used something like this? 

 

[Stoik]

To recharge a modern phone quickly, you will need a 5 volts USB output with 1 ampere current. The phone will fully charge itself in about 4 hours with that power available. Most of good phones are using 3.7 volts and less than 2 amperes/hour (2000mA/H) capacity batteries.

To build a solar project, it's very important to know 3 things:

1- What load you'll need to power up and for how long?

2- What is the effective solar production time in your area of the world?

3- Where are you planning to deploy your solar project?

On point one, you'll need to know what is the exact load of your phone or other USB rechargeable devices. A good way is to check what is the battery in it. Use this site to find more about it: http://dantona.com/index.php

What we are looking for is Watts. Solar power calculations works with watts. So the basic formula to know this is P = U * I. P stands for power (watts), U is for voltage, and I is for amperage. Let's apply this formula on an iPhone 4S battery: 3.7 (volts) multiplied by 1.45 (1450mA/H) = 5.37 watts

But nothing is perfect in this world, so the internal resistance of the battery, the internal power consumption of the charging device, etc... makes that you'll have to roughly add 30% more to your power load to achieve real world results. So 5.37 watts is now a 7 watts load for your solar project, and that,s for every seconds it is connected to it for recharge.

For the second point, you need to know for how much time you could expect your solar project to be efficient into its charging time. Check it out here: http://www.freesunpower.com/radiation.php

So to charge a 7 watts load in 4 hours every day, you'll need to produce every day at least 7 watts during 4 hours, right? Wrong! You'll need to produce at least 3 times that amount of energy. Why? Because it's not always sunny outside, and the efficiency of a solar panel is affected by numerous factors, especially heat and shadowing. So you're not producing energy optimally 3/4 of the time on a normal daytime. So you'll have to think about making energy storage for at least 3 times the usage of your load, and be able to produce it 3 times faster than your load can consume it. however, that's only true for an everyday usage, because if you don't apply the load every day on your solar installation, that spare time could save you hardware on the production side of things.

More to follow, I need to play now.

[butt]

Solar Radiation : Sunshine across the United States =
My location is 5.5

Items to charge?
i4 & i5
Both show 3.7v & approx 1450 mAh
also an older iPad (not sure of model#)

[Stoik]

The Ipad requires like the iPhones a 5 volts source, but with more current, idealy with 2 amperes available. So you'll need about 5 amps at 5 volts for 4 hours to charge up all your 3 devices at once. 25 watts during 4 hours.

I don't know if you really require from the solar kit to be portable, like the one into a CD carying case and tin foil box, because if you don't, I could propose you a better and more standard way to do things.

As I barely burbled to you on TS the other day, there's many flaws in this design. The voltage is not high enough with only 4 1.2 volts batteries, the casework is not suitable for the usage, and the concept is not made to be reliable at all.

So what I would suggest is to make it a standard 12 volts design. You'll have a standard sealed lead acid battery charged by a MPPT charge regulator like this one: http://www.blueskyenergyinc.com/products/details/solar_boost_1524ix . A MPPT charge regulator is more expensive than an ordinary one, but it's way more efficient with the energy it receives from the solar pannel. Because instead of simply dumping everything over 14.4 volts (the correct voltage to charge 12 volts batteries), it will recycle it into more charging energy. Most of modern solar pannels are way over 18 volts on their outputs those days, so a MPPT charger will be roughly 20% more efficient than a regular charger.

Here's a clearer explanation of the calculations I made above: http://www.wikihow.com/Set-Up-a-Small-Solar-(Photovoltaic)-Power-Generator

The solar pannel will need to be correctly oriented and located at a place idealy free from shadowing. So a portable solution is far from ideal for the energy production side of the project, IMO. You could make it easy to carry, but not to follow you all day long. However, the charged batteries could follow you... and you could have many of them, and of multiple sizes (and weight).

I would suggest you to go with two 30 watts solar panels. That will give you more flexibility than just one 60 watts panel for the size and charging capacity of the batteries you could use (and you could start with only one, it's softer on the budget). Here's a quick overview of what's available on the market: http://www.mrsolar.com/page/MSOS/CTGY/wattsort

For battery packs, I would suggest for the first one a battery that could idealy have a 4 amperes charge (14.4 volts from two 30 watts solar pannels), able to cope with a "slow" charge of 2 amps (a single 30 watts panel), and able to deliver a medium current drain, like the PG12V35 from Powersonic. http://www.power-sonic.com/images/powersonic/sla_batteries/pg_series/PG-12V35_11_Jan_12.pdf

You'll fully charge this battery in about 3 days with two 30 watts solar pannel and your 5.5 rate (you have the sun efficiency equivalent of a SSD versus HDD compared to me up here, LOL!). This battery can charge all your devices 4 times before being drained out. 12v x 35a = 420 watts theoric supply capacity during one hour (no, it can't do that in real life).  So you'll have more than your 3 days autonomy right there, as your load is 25 watts x 4 hours = 100 watts/hour. 420 divided by 100 = 4.2 times.

With one 30 watts panel, you could use smaller batteries to increase the portability factor. So with one lighter plug adapter that you fit on the battery, you're plugging a 5 volts and 2 amps USB adapter like this one: http://www.amazon.com/Lenmar-AIDCU2-Charger-Smartphones-Tablets/dp/B004UBSGS8 you simply plug your iPhone or Ipad USB cable into it and tada! Enjoy solar energy.

Of course, there's many conception details that need to be clarified, and I'll be happy to oblige.

Regards,

Stoik

[butt]

I don't know if you really require from the solar kit to be portable, like the one into a CD carying case and tin foil box, because if you don't, I could propose you a better and more standard way to do things.

Nope, does not need to be so small. Just thought the 'altoids box' idea was pretty nifty.

I would suggest you to go with two 30 watts solar panels. That will give you more flexibility than just one 60 watts panel for the size and charging capacity of the batteries you could use (and you could start with only one, it's softer on the budget). Here's a quick overview of what's available on the market: http://www.mrsolar.com/page/MSOS/CTGY/wattsort

Given my current state of affairs, all of this hardware is well out of my budget, but great info! Thx
How about this one? Could get three for the price of one 30w listed on the above link. Or, one panel w/out breaking the bank. 
http://www.ebay.com/itm/251349923346?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649


For me, a project/discussion of this nature is more of a "learning experience" than an actual build/purchase plan. Things of an electrical nature have always been a very soft spot in an otherwise solid construction background. If I can learn the ropes (requirements) of solar energy production/storage on a small (inexpensive) scale, that is knowledge that I'll always carry with me.  Think of it as the "Teach a man to fish" philosophy. 

Thanks for the great feedback. Your links will provide plenty of good reading. Much appreciated.

[Stoik]

My pleasure!

The panel on the link you're showing is OK. But I would go for the this kit from the same seller: http://www.ebay.com/itm/COMPLETE-KIT-30-W-Watt-30W-30Watts-PV-Solar-Panel-12V-Volt-RV-Boat-Off-Grid-/261299119073?pt=LH_DefaultDomain_0&hash=item3cd6a423e1

You'll get the brackets to install the panel somewhere, the cables to connect it to the charge regulator, and of course the charge regulator.

You pick a used car battery at your local scrap yard (with date code inferior to 3 years back),Get the 12 volts USB power supply I proposed you above, along with this: http://www.equipt1.com/rendition.product/Company%20Product%20Images/National%20Luna/Battery%20Accessories/Battery%20Clips%20with%20Cigarette%20Lighter/Cigar%20Socket%20with%20battery%20clips.png

Done!

Regards,

Stoik

[butt]

Andy. This is topic I'd like for you to revisit. Seeing that the cost of this stuff has gone down since we last discussed it, wondering what kind of kit you'd recommend now? How about best option at $100, and best option at $200.

Oh, might check your links in your above post. Not sure they all are still working. thanks

[Stoik]

For 200$, you could get this: http://www.ebay.com/itm/Solar-Panel-KIT-Panneau-Solaire-100-Watt-Poly-W-MPPT-charger-cable-MC4-BOAT-RV-W-/300927634205?pt=LH_DefaultDomain_2&hash=item4610af4b1d

What you get there is a polycristaline pannel instead of a monocristaline type. This mean a better behavior regarding heat management, and less heat is less internal resistance, less internal resistance means more energy for you out of the same power rating. It's no big deal, but 5% more is 5% more when it's over 30 degrees celcius out there.

You also get a MPPT charger/regulator, and that's a great improvement over a PWM charger/regulator. You'll get up to 30% more energy out of the same panel, due to a significant efficiency gain into the energy's conversion technology. PWM will discard about everything over 14.4 volts. It's not relevant with panels of 50 watts or less, because the output voltage arriving to the charger/regulator is close to that 14.4 volts. But with a 80 watts panel or more, you'll get usualy 18 volts or more. So with PWM and a 100 watts panel, it's 18.9 watts that get dissipated as heat into the inefficient regulator. 

You will still need good batteries of the "deep cycle" type (and this is usually the most expensive part of a solar project). Golf cart batteries are a good example. If they are 6 Volts type, just get two and hook them up in serial to get 12 Volts.

Hope this help.

Bye.

[butt]

Thanks Andy. Mucho gracias senor.

Another thing I've also been looking at is wind a powered generator (wind mill) Could a set up like this be used in conjunction with a solar battery system? As in can I charge the same battery bank with two different power souses?

Something like this (but I would do a DIY build)
http://www.ebay.com/itm/321320029380?_trksid=p2060778.m1438.l2649&var=510230194867&ssPageName=STRK%3AMEBIDX%3AIT

[Stoik]

You usually can't charge the same bank of batteries with two chargers, unless you install a selector switch to choose the charger you like. You often see this on boats or RV vehicles.

There's no major problem at mixing solar and wind power, but you'll need a different type of charger/controler, a "hybrid" one, and it's usually (and fairly) more expensive.

I can't see your eBay link, thanks to geoblocking...

Bye.