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Solar Phone Charger Question Answered


I'm fairly new to electronics and am trying to put together a solar charger from the many instructables here.

I am using 2 35mAh solar panels wired in parallel to charge a 2600mAh LiPo battery.  I understand this will take days (right?) to get charged fully, but how can I tell that the panels are wired correctly and charging the battery.  I am hoping to make this as a Christmas present and would hate to give this to someone and have it not work.

I am using a cheap Lithium Charge Controller I got from ebay and am wiring the panels and battery and usb charger to that.

Thanks for the help.


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8 years ago

Argh! I wrote a whole essay and pressed STRG-R which is "reload"... all gone... :(
Well then... again:

First: Congrats on buying an actual charging curcuit and not trying to just connect Panels to LiPos which i have seen in the past be tryed multiple times (Never works savely).

To answer your second question: The charger tells you! :) "Led indicator: red is charging blue is full charged."
To answer your first question (Charging-duration9 you simply divide the capacity of the battery by the supply-mA. By normal math there should come out a number and as type "h":
2600mAh/35mA=74.29h. Lets assume, you have 6h of usable sunshine each day, this would mean you need more than 12 days of constant charging (6h/day) on the maximum current your panels can deliver (35mA) to charge the battery.
Even worse: The battery itself will self-dicharge a bit during those 12 days, making it even longer. Also this assumes that the charging-controller is 100% effective which is NOT the case.
So i think go with something around 76-80h of charging for a full battery.

Here are some additional hints if you still want to make it:
- Be sure your panels can generate the needed voltage (4.5-5.5V) for the controller.
- Be sure you protect the controller from overvoltage (if it is possible for the panels to generate more than those 5.5V specified as max voltage of the controller). Such thing can be accieved with a simple "Adjustable low dropout linear regulator" like the LM3080 from http://www.linear.com/product/LT3080 (you can order free samples there BTW!).