I was inspired for this project by the new, brighter solar-charged landscaping lights that are available these days. They actually put out enough light to illuminate a pathway after dark, so I wondered why I couldn't do the same thing for indoor use?

Most evenings I'm either watching TV or a movie, working/playing on the computer or chatting with friends; none of these activities require a huge amount of room light. Generally I put a light on low just to provide enough illumination to avoid tripping over the cat when I go to the bathroom. I have a pocket LED flashlight with a single 3W Cree LED in it, and it seemed to me that it put out plenty of light for low-level illumination of my living room for those sort of activities. So I created an LED room light with a rechargeable battery in it, and installed solar cells to recharge the battery. I prop the unit outside in the sun when I go to work in the morning, and in the evening it's charged up and ready to light up my living room.

Update: I've been poking around and I see that I'm far from the first person to have this idea -- there are a lot of very nice "sun jar" designs which I was unaware of. I think my room light is different primarily by having a larger battery and solar collecting area, which allow it to drive the LEDs much harder and put out a lot more light. My unit is very esthetically challenged compared to most of the sun jars, but it's much brighter.

Step 1: Battery

This is the battery I chose to use; it's available at http://www.all-battery.com/li-ion1865037v2600mahrechargeablebatterieswithpcb-1.aspx. It's a single-cell lithium-ion battery with a nominal voltage of 3.7V and a rated capacity of 2600mAh. What makes this battery fairly unique is that (as can be seen in the picture) there's a small round PCB underneath the plastic sleeve of the battery, which contains an IC that protects the battery against severe overcharge or over-discharge. If the battery voltage drops below 2.5V, the IC disconnects the battery from the load and will only reset when a charging current is detected; if the cell voltage reaches 4.25V  the charge current will be shut off until a load current discharges the battery somewhat. Unfortunately these thresholds only protect against severe mistreatment -- they allow moderate abuse to the battery which can pretty quickly shorten the life of the battery. I'd like to find a self-protected battery that keeps itself better protected, say with thresholds of 3.0V and 4.0V, but it doesn't seem like there's anything available.

Because of the embedded PCB, it's not a wise idea to solder directly to the battery (and anyhow that's a lot of heat for a Li-ion battery), so I sprang for a battery holder, and soldered to the leads of the holder instead of directly to the battery.


Great work middlenamefrank! I've been trying to make one of these for my place but from more of a designers point of view, i don't have the electronic engineering background. Would you be interested in a colabo?
What exactly would you like to collaborate on? I'm pretty happy with the way it works.
So is this still not entirely complete? What's still missing?
Uh...well, I guess it is pretty much complete. I do intend to add a long-term report on battery life and how much/if it degrades over time, but that will necessarily take a while. <br> <br>I also originally planned to build another one, and show it going together, but contract work is overwhelming me right now and this has slipped down the priority chart. I may not build another one at all, and if I do it will be a while.

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More by middlenamefrank:Building a Fire With Purchased Wood Showstoppers Solar recharged LED room light 
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