A Brief Introduction:
My children are now in their teens, and as I have watched them grow I have also watched the complexity of their "toys" grow with them. My house is now full of wall warts of every description charging everything from Wii remotes and cell phones, to notebook computers and flashlights...not to mention cordless tools :) No one ever unplugs these charging devices so they silently keep adding to my electricity bill. This incessant drain of electricity has bothered me for a long time, not just from an environmental perspective but from a monitary perspective as well. I once came across an article that suggested nearly 40% of our home Electricity bills are due to "phantom loads" such as wall warts and instant-on devices. This Instructable outlines my attempt at curbing some of the drain from phantom loads in my house.
Step 1: List of Materials & Tools
In the spirit of cheapness which inspired this Instructable, I have tried to source most of the required parts by salvaging them from around my house, and borrowing them from other projects. In some cases I have noted where I originally purchased them.
12 volt Automotive battery (later to be swapped out with 12 volt deep cycle batteries)
Metal Rolling File Cart (I found this hanging around in my basement...I think it was originally purchased at Staples)
200 watt, 12 volt inverter with Alligator clamps (I found this in the trunk of my wife's car...she'll never miss it. Philips)
3 Automotive Solar Trickle chargers, 6 watts total ( I bought these in a clearance bin at Princess Auto a few years ago)
Battery Post Terminals (Princess Auto $6.00)
10 Gauge insulated solid wire (Had it kicking around in my shed)
110V AC USB Charger (re-purposed from my blackberry playbook...it has a higher than average output current capacity)
4 port USB hub (Not shown in this Instructable)
Switched AC Power Bar (Hardware store $3.50)
12"x16" Tray (Value Village, $2.99)
Sheet metal Screws
Soldering Iron & Solder
Step 2: Wiring Diagram
The wiring for this project is very simple. The 3 solar chargers are hooked up in parallel with each other. I used a multi meter to determine the output polarities of the chargers. The chargers are then hooked up to the battery...positive to positive and negative to negative. There are diodes in the chargers to prevent the solar cells from drawing power from the battery when the sun is down.
I was going to use a switch to isolate the battery from the inverter, but at this point I simply disconnect one of the alligator clamps at the battery. When the system is charging the battery, I don't want any draw from the Inverter.
I then plugged the AC power bar into the AC output of the Inverter to give myself five 110V AC outlets limited to 200 watts in total. Now, I can plug the wall warts into the power bar and charge whatever I need to charge.
The inverter is internally fused so if the kids plug too many devices into the power bar, the inverter shuts down. My Lenovo notebook charger draws 90 watts, and my Dewalt 18V battery charger draws roughly 50 watts. I try to keep the total power draw under 175 watts from all the devices hooked up to the system. There is also a low voltage alarm on the inverter when the battery drops below 12 volts.
Step 3: Construction:
The File Folder Cart had to be slightly modified to strengthen it. I added a few sheet metal screws to the frame to stiffen it up so that the unit could withstand being rolled around in my house.
I then drilled holes to screw the Solar Chargers to the file folder frame and screwed them into place.
Next, I wired the chargers in parallel and cable tied the wires to the metal frame of the cart. I used 10 gauge solid wire to connect the chargers to the battery terminals. The Inverter connects directly to the battery terminals with alligator clamps...paying attention to the polarity. If you reverse the polarity you will fry the Inverter. I cable tied the Inverter to the bottom shelf of the Cart to secure it.
The Power Bar simply plugs into the Inverter. I cable tied the wire for the power bar to the cart and and also tied the power bar itself to the tray to secure it.
Step 4: Construction Photos:
Step 5: Its Alive...Its Alive! ...and Some Random Closing Thoughts.
I know many of you out there are probably scoffing at the 6 watt maximum output of the solar panels. Let me just say that this project is a start in the right direction. It may take a few days to charge the battery but it takes a few to drain it as well...and all that energy is free! I roll the unit out on my front porch to charge it. I just leave it in the sun all day and it does its thing. The kids think its cool and they are actually using it which is something I hadn't expected. Its also great in a black out. We hook up a couple LED lights to it...who needs candles anymore. Regardless, the little "power cart" gets rolled around our house charging whatever it can.
I am looking for a 20 watt solar panel to replace the little trickle chargers but they are hard to find on a zero budget. Installing that will also require a charge controller...something else that will require some time to find on the cheap...or I could make one...hmmmmm.
The car battery was just an extra that I had kicking around in my shed. This spring I intend to visit a Boat Marina or two and dig up a couple of deep cycle batteries. The spring is a good time to get discarded batteries that still have tons of life left in them. A deep cycle battery would certainly be better suited to this application.
Most small Inverters that I have used draw power even when the switch is turned off. It is important to disconnect the battery from the rest of the system when it is not in use...the Inverter will kill the battery even if it is turned off. I will likely install a SPDT switch between the battery and the inverter.
Step 6: Closing Photos
Although I have been a member of Instructables for many years, this is the first Instructable I have ever written. I am entered in the Portable Workstation Contest so if this 'ibble has inspired you to build something similar or if you found it worthwhile reading, please vote for me.