Hello. First time poster, many-a-year browser. I will describe my current project in the fullest detail I can and follow it with my attempted solution. I will point out off the bat that while I have a BSc in Mathematics, I had a terrible time learning physics in high school and get stage-fright when trying to recall/work with the necessary formulas. So, I have a 13W solar panel (with controller integrated) hooked up to an old car battery. Testing with load it shows good amps and steady 12.5 volts. My guess is it could actually start a car so long as it wasn't below -30. From this car battery I have a fuse block set up which allows me to tap into the battery for various things around my yard like rain barrel pumps and lighting. Few days ago, I bought 10 of those dollar store stakes with the pumpkin face on them. Essentially, it is a plastic decoration with a very simple inside. An incandescent light bulb marked with 2.5V 0.3A that connects directly to 2 AA batteries. So, I figured, if I wire 5 together in series then connect this to my solar power set up, I should be pulling 12.5 Volts at about 1.5A. (I Have NO idea if this is correct because my physics skills are so weak) But, I have fused the power source with a 5 Amp fuse currently and it isn't popping, so clearly it is under 5 amps. Oh, btw. they light up beautifully. I don't know the resistance of the light bulbs nor how to find it....... So I am lost. What I want to know are two things. 1) Can I hook up another identical setup in parallel to this one? And if so, what will the current draw be? 3A? (Also, will the resistance be reduced by 1/2??) 2) And perhaps of more interest to me right now, How much power are these drawing? For solving part 2) I thought since P=IV, I am pulling 18.75 Watts. I don't really understand where to go from here. I guess that per second I use 18.75 Joules? What I am concerned about is: If I leave the lights plugged in (either the single strand or double strand) for 24 hours a day, am I going to deep discharge my battery? Will a solar panel with 13W rating manage to recharge the battery every night enough that it wont matter? SO! Basically. Milk and cookies for anyone who can walk me through this. I would love someone with the "Teach a man to fish" attitude. My skills in science are pretty basic but my math skills are basically all I have going for me, so I am damn good at it. I would love to learn more about electricity and how all the formulas inter-relate and the like.