RaceR86: Thanks, every once in a great while the photo gods give up a good pic, most of the times not. Hope you get your flash grenade lite done. Click - Boom! -blinding light.
What a great build. Nicely finished and with time to spare.
Interesting…might need a few mods
A. Port for 5vdc charging from a computer “just in case”
B. Port for 12vdc charging (thru a regulated output of course) in your car “just in case”
solar can be used to keep it all topped up (how long do you think it would take to charge the battery from full discharge with those two plates?
very interesting build for sure 
I was thinking of adding a charging port at one time, but more for the hobby charger. 5V & 12V charge ports certainly something to consider as an update.
Just a guess, maybe 2 1/2 to 3 days of full sun for a full charge? The capacity of the battery pack is 2500 mah. I will try and follow up when the sun comes back out. The idea is that the lite would be sitting in the south facing window sill, waiting for the odd power outage. They always come around when the thunderstorms start up in the summer.
Very cool
What charge controller do you have on the Li Ion pack feeding from the solar cell?
Very good question. The PIC 16f1827 is the controller. At this very moment the pack is unregulated. Outside of the voltage display (manual regulation) there is no over voltage protection. Continuous solar power will eventually overvolt the pack. The good thing with a LifePo4 battery is that it will not catch fire. The effect of overvolting the pack is a much shortened cycle life.
A hardware fix for this overvoltage (3.6V for LifePo4) condition is to short the PV panels with an NFet. The battery is not affected because of the schottky blocking diode that is currently in place to prevent the battery from discharging at night.
A simple software solution is just to burn off the excess voltage, by actually turning on the led for short time, then check voltage, repeat as necessary.
I’ll post back if I get the NFet, or software fix, in place before the end of the contest. The judges can dock me for the oversight if I don’t.
How'd I miss this one. I just noticed it in the contest thread. Nice work nickelflipper.
Thanks again everybody.
WarHawk-AVG: I have tested a software solution that I think is going to work for the overvoltage protection of the LifePo4 battery pack. Put a 14500 Li-ion at 3.76V, and after some number of minutes, the voltage was pulled down to 3.68 and blinking the 888’s on the display every ten seconds or so. When the test was first started the display was blinking on and off every 1 sec. The 3.68V slowly rises due to battery bounce back, till it trips the 888 on the display again. The accuracy of the internal voltage measurement is in the 20-30mV range.
Excuse the lack of tabs in the below code. I don’t know how to handle them in this editor, or even if it can?
Main:
RefVolts = AD16f1827(FVR) ’internal a-d of FVR
BatVolts = 52224 / RefVolts
If BatVolts > 365 Then
Call DisplayNum 888
else
If mode > 0 Then
Call DisplayNum BatVolts
else
BlankDisplay = True
Call DisplayNum BlankDisplay
end if
end if
wait 1 s
Goto Main
Nice work!
Now that I’ve finished mine, I have time to read through all of the other build threads in more detail.
Nice, very cool, keeping the battery protected from overcharging while being able to be continuously ready for use…how awesome is that!
6/29/14 Update - Solar charge test #2.
So same test as previous one which was 5 1/2 hrs from virtually the same time frame of 11:15am to 4:45pm. This time the weather was cooperating much better, with the test starting with partly cloudy conditions early on, to mostly clear later in the day. The battery pack was once again discharged by the Thunder AC6, then solar charged, then discharged at 0.5A (approx. medium mode) once again to get the mah packed in. The #2 solar charge test produced 835mAh, hurray! So three days of similar conditions would put a full charge in the 2P 18650 LifePo4 pack (1250mAh ea.).
Beautiful light build and could be very practical around the house for power outages, love the design.
very cool design that incorporates free-energy to generate its on power.