How can this solar Charger charge Iphone? what is inside?

[antennaboy]

Hello Forum,

I have a basic question about trickle charging an Iphone after reading the article

http://www.ladyada.net/make/mintyboost/icharge.html

The article seems to state that it is not so easy to trickle charge an Iphone.... This solar charger I found online seem to have no problem charging the Iphone:http://store.solio.com/Solio-Store/Solio-Bolt-Solar-Charger-S620-AH1RW

What do you think is inside it? I believe there is a battery. The solar cell charges the battery which later charges the cell phone. There must be a DC-DC boster to give the phone (USB device) its needed 5V....

What else?

thanks,
antennaboy

[adafruit_support_bill]

That unit does not trickle-charge the phone. The internal LiPo cell is charged by the solar cells. Given the size of the cells, that could be considered a 'trickle' charge.

Once the internal battery is charged, a boost converter (similar to our own MintyBoost) converts the 3.7v nominal output of the LiPo cells to the 5v @500mA that the phone expects from a charger.

[antennaboy]

Thank you adafruit!

In essence, it is the internal lithium polymer (LIpo) battery that, once it is charged enough to its nominal 3.7V, trickle charges the phone. But is that trickle charging in that case or can we call it regular charging at a slow rate? Maybe a cell phone always trickle charge once its total charge is high enough...

If we had more solar cells connected in series, then we could get a voltage high enough for the booster to convert it to 5V, correct?

Does the Iphone really need 5V AND 500 mA? What if we provided it with 5V and 200 mA? Would we still be able to trickle charge the phone?
But, I guess, that would not happen because if the load (phone) gets 5V, automatically its internal impedance makes it draw exactly 500 mA, correct?

I think there are cases where, even if the voltage applied to the device is the correct one (5V in this case) the drawn current is not equal to (5V)/(load impedance), because the source, although it can provide the 5V, may have a max output current of, say, 300 mA...

Thanks,
Antennaboy

[adafruit_support_bill]

The only "trickle" is the charging of the internal battery. More solar cells can make that happen faster. When it builds up enough of a charge on the internal battery, it can charge the iPhone at the rate it expects (500mA).

We can't control the phone's appetite for current. It has its own internal charge controller. We provide 5v and it tries to take what it wants. If we can't provide enough current for it, the voltage will drop below 5v and the phone will drop out of charge mode.

[antennaboy]

Ahh, thanks, now I see.

I also like your analogy. So if the Iphone does not get BOTH the voltage and current it wants, it does not eat anything. Sound like a toddler.

So, the power the phone wants is (5V)*(500mA)=25 W. If we provide it with only 10 W, then it does not want to eat the 10W?

Also, the phone can be seen as a load with a time-changing impedance: as the phone battery gets more and more charged, the impedance increases and less current is needed and drawn, correct? It does not have to "eat" 25W of power the whole time, correct? Or is that 25W really what it eats in trickle charge mode?

Adafruit, what do you think about this charger? A friend just passed it to me. What do you think?
http://www.foxoffer.com/4200mah-polymer-lithium-battery-solar-charger-bank-p-137.html#.USpyoFpAT6k

Can you help me determine how it is better or worse than the Solio one?

http://store.solio.com/Solio-Store/Solio-Bolt-Solar-Charger-S620-AH1RW

Thanks for the patience,
Antennaboy

[adafruit_support_bill]

A typical charge cycle may start at a low rate, then ramp up to a high-current fast-charge mode for the bulk of the charging. Often there is a 'trickle' phase at the end as it reaches full charge.

It is hard to compare the Solio and Fox chargers directly because the web pages do not provide specifications for all the same parameters. The Fox version appears to have twice the capacity, but takes 14-20 hours to charge by the sun. You also have to take the specs with a grain of salt. Battery capacities are often overstated and solar cell output frequently assumes sun equivalent to high-noon in Phoenix.

For more insight into how these things work, you may be interested in reading through our tutorials and design notes for our solar charger http://learn.adafruit.com/usb-dc-and-so ... sign-notes
and our Mintyboost boost converter. http://www.ladyada.net/make/mintyboost/

These two kits are are often combined to make a solar phone charger, much like the ones you are asking about.

[antennaboy]

Thanks again.

I will read the tutorials.

You are right, there is a lot of stuff out there:

http://www.espow.com/wholesale-16-000mah-high-capacity-solar-panel-charger-for-laptop-31-unique-adapter-tips.html

to charge a phone, laptop,

and this one for $5 only,

http://www.tmart.com/Lighter-shape-Solar-Battery-Charger-for-iPhone-White_p105655.html?fixed_price=us_us&utm_source=base&utm_medium=organic&utm_campaign=product&gclid=CPXTjYbtz7UCFcme4AodXHsArg

I am tempted to buy a few ones and break them apart to see what's inside.

Best,
Antennaboy