Charging a Kindle from a small panel

inthejungle · June 2015

Thanks for your help- I am wondering if anyone has any ideas

I have a buddy living in the middle of no where. He recently got a few small panels from someone and wanted to see if I could put together something very simple to charge his phone and Kindle.

He doesn't want to run a genset and he doesn't want to make a big system, he and his family are working in the desert in Africa.

The panel is a Koncar
p= 4.0w Voc= 22.5 Isc 330ma Vspec 14.5v

The model of Kocar panel is KSMMAL 112,

He has four of these so I thought I about running a small charge controller, then into a small battery, and out to a USB outlet for a truck. this would allow him to charge phone and Kindle off the USB.

Any other ideas or thoughts?

Thanks

BB. · June 2015

That should work fine... There are some options out there where you can get USB chargers that work direct from a solar panel--Cut out the 12 volt battery....

That could be a good thing (save the cost of a small 12 volt battery which will need replacing every couple of years, a volt meter and/or hydrometer to keep track of battery state of charge, etc.). But this means can only charge during daylight hours--Having a 12 volt battery allows charging anytime in any weather.

Not a right/wrong answer--Just depends on the needs of the user.

-Bill

Brlux · June 2015

I have done some playing with direct charging from a 5W panel using a USB car charger and no battery. It can work with some limitations. If a cloud comes by or something momentarily shades the panle the charging may not automatically recover at full power when the sun comes back, requiring unplugging the USB cable and then plugging it back in. This is because the charging setup relies on the high voltage from the panel to get the watage needed. When the voltage collapses the charger draws maximum amperage the panel will provide and never lets the panel get back to the high voltage where higher power is produced. Same thing hapens whenyou try charging a device that draws more power then the panel can supply at that moment. Adding a large capacitor on the input of the USB charger can help the charger run better. I would probably recommend a panel twice the watage of the USB deviced being powered.

The Kindle may work out with the 4W panel but most smart phones draw 5W when charging.

Here is the car charger I like, it is rated up to 24V most panels are going to be in the low 20 volt range when no load it attached.
http://www.amazon.com/Anker-Charger-...er+car+charger

These USB meters are very handy for seeing how the charging is working out.
http://www.amazon.com/Estone%C2%AE-C...ords=usb+meter

Alternatly I have one of these USB panels. They work great for charging a phone or other USB device but the fabric design may not hold up well if left out in the elements long term.
http://www.amazon.com/Anker%C2%AE-Dual-Port-Charger-PowerIQ-Technology/dp/B00E3OL5U8/ref=sr_1_1?ie=UTF8&qid=1434472478&sr=8-1&keywords=anker+solar

BB. · June 2015

I have a few of the Anker products (several 12 volt 2 port USB car charger, a couple of there larger USB battery packs, and a couple of their 120 VAC chargers, as well as a different brand of USB volt/current meters).

Their products work well... I did have a 5 port 120 VAC charger fail (I think they had an overheating/design problem)--But they did replace it just fine (mail the bad one back) inside of their 18 month warranty). And the old model seems to be superseded with newer designs (and hopefully better).

The USB volt/current meter--Very handy and easy to see how everything works and figure out if you have a bad cable (or bad charge controller in my case)--Very little debugging information from USB chargers in general. I would have saved a "bad tablet" vs what turned out to be an intermittent USB charger. So far, my android phones/tablets seem to take ~1-1.5 amps to charge (depending on device, and my Samsung S5 phone will cut back to 1 amp charging when the display is on--I guess to keep heat build up down--LED's + battery charging could overheat phone at 1.5 amps current).

Lastly, while I like the large capacity USB battery packs for charging (my kids take mine all the time to charge their and their friends phones on trips)--Mine pack is 12,000 mAH (12 AH @ 5 volts) and at a 1 amp charging current takes >12 hours to recharge. So--make sure you plug that into your usage/charging equation (i.e., you have 4-6 hours of sun, it will take 2+ days to fully recharge in good sun).

-Bill

Brlux · June 2015

Just for clarification all the external USB battery packs like to rate size in mAH when in reality they should be rating in watt hours. The mHA rating is for the cells in the pack, so 12,000mAH would be at a nominal 3.6v from the battery. You will get far less than 12,000mAH at 5V from the USB port. I took apart one of my Anker 12,000mAH packs and it had 4 18650 cells at 3,000mAH each. They were actually in a 2 series 2 parallel configuration.

The USB battery packs are a nice way to buffer power from the portable solar panels for use at your convenience to charge your mobile devices. The one down side to most of them I have seen is you can't charge the pack and output power from the pack at the same time.

BB. · June 2015

Hmmm. Marketing exaggerates again.

Not happy. Not surprised either.

-Bill

2twisty · June 2015

Send him something like this?

http://www.harborfreight.com/5-watt-...ger-60449.html

or this:

http://www.harborfreight.com/13-Watt-Briefcase-Solar-Charger-68750.html

inthejungle · June 2015

Thank you for all of your thoughts- I am on the other side of the world so I haven't posted responded yet. The car charger looks like it would work well, what do you think should I make a small shelf and put a few car Cig. outlets in there then a few of those?

zoneblue · June 2015

If you enjoy the challenge rigging a 7AH gel cell, a small PWM controller etc can be a lot fo fun and a great learning experience. However having been there and done that, ( we have something like this in a shed powering an electric fence, the battery contacts require regular cleaning, the gel cell has to be replaced quite often etc), i would just buy one of the portable panels with a USB output, and a lithium power bank. The price of these things has halved in teh last two years. I got an 13W Eceen panel off ebay for $50, and the Xiomi 16Ah power bank of deal extreme for $25.

A 7Ah gel cell alone costs $40 plus shipping.

Charging a Kindle from a small panel

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