Well I finally finished our solar panel setup after months of baby steps! When we last left off in Part I, the solar panels were on the roof but nothing else was set up. Well it turns out that although installing the panels was the most nerve wracking (because we drilled holes in the van) the rest of the install was tricky and required a lot of figure checking and slow steps towards the end goal – working power in the van!
Baby Step 1: Wiring the Solar Controller
In my last post I talked about cutting the holes in the roof for the cables that connect the solar panels to the solar controller (the thing that keeps the panels from zapping our battery too hard). I decided not to hook them up to the solar panel or the controller at that point since I didn’t have the batteries yet and leaving the wires live even with the controller there seemed like a bad idea. So once we got the batteries delivered it took two seconds to hook up the solar panel and the controller AND……nothing. The controller didn’t turn on. I was desperately hoping that this was because the controller needed to be hooked up to the battery as well to turn on so on to the battery install!
Baby step 2: The batteries
I bought 2 AGM deep power cycle batteries to go with our solar array. Each battery is basically a golf cart battery that can store 210 amp hours of energy. I had to buy two however because each one was only 6 volts. By wiring them in a series I got essentially one battery bank with 12 volts and 210 amp hours. (Wiring them in parallel would have given me 6 volts and 420 amp hours because math) These are a little more expensive than their lead acid counterparts but they have the benefit of not needing a water bath and not venting any gases as they charge. I know that plenty of people have no problem with watering their batteries every few months – but I just wasn’t too comfortable with the thought of sleeping on top of venting batteries or throwing heavy music equipment around near electrically charged acid water.
Each battery weighs 60 lbs so getting them into place was a bit of a challenge. I initially wanted them to be as close together as possible but the space available in the van just wasn’t working to place them side by side. I ended up placing them on either side of our storage cubby in the rear of the van. This keeps the weight balance pretty even which is good for our tires and the wiring to connect them isn’t too crazy. Just in case, I made sure to use the 6 gage rather than 8 gage wire to compensate for the extra distance.
Since Kevin and I sometimes make our own instrument cables we’re pretty familiar with working with cable connections so installing ring terminals on the cables was pretty easy. You can use a wire clipper to carefully cut through the outer insulation layer and pull it off to expose the bare wire. Place your ring terminal over the top of the exposed wire, clamp in place, and voila! Electrical wiring.
Once we connected the batteries in series we wired in the solar controller and EUREKA! The solar charger turned on and started showing a healthy 12 volt flow into our battery bank.
Baby Step 3: Wiring the Inverter
So now we had a working power system and what appeared to be fully charged and happy batteries. The “fully charged” part still kind of remains a mystery to me since there is no nice button that blinks when the system is fully charged. What I have learned thus far is that when the voltage readings show above 12volts (ours shows up to 14) the battery is completely charged. Once you pass a current through an inverter and the batteries start sending power, the voltage drops to 12 and holds steady. If the battery charge is critically low or you’re drawing more power than the system can handle the voltage will drop down to 11 or 10 which is BAD and you should stop doing whatever caused the drop – either by turning off appliances or letting the batteries get back to full charge.
But before you can start running basic appliances you typically need a power inverter. An inverter changes your 12v system into a 110 or 120 volt system. Different inverters are rated for different kinds of wattages and power draws but I chose a pretty damn nice one that outputs 110v and 1500 watts. This should be able to run most basic low wattage appliances as long as we use them carefully and don’t run down our battery. 12v appliances run great on this system since their power draw is very low. I made some new wires and hooked up the inverter system AND…..A WARNING CHIME!? WTF?
I could not for the life of me figure out what the HELL was wrong with my system, I thought I did everything right! Then I talked to my dad (who’s been a big help figuring this stuff out). We walked through the wiring system and I made a big stupid error putting it together. Somehow I thought that when you wire batteries in a series (you connect a positive lead of one to a negative lead of the other) you’ve now created one big battery and they’ll just do their happy battery thing. But I had wired the inverter in PARALLEL with only one battery and the second was just sitting there useless. This meant that my inverter which was expecting 12v was only getting 6v and was freaking out. Here is a diagram of my mistake below – I admit this mistake so that future solar nerds will not repeat it:
So once you have batteries wired in a series – every other piece of wiring has to follow that same series pathway. Oh the things you learn…..
So now it was time to test out our appliances! We have a little 12v iceless cooler that plugs into a cigarette lighter in a car so I knew it would run just fine – and it did! Our little fridge turned right on and started humming away. Then I tried to run our hot water heater (coffee is not optional for me). It immediately bottomed out the voltage and sent the inverter into a panic. Soooooo…..not so great. I checked the power specs on our water heater and it turns out it draws 1500 watts. So although our inverter is rated up to that level it really doesn’t want to have to push 120v at 1500 watts for more than a split second. So I went online and located a water heater that only drew 1000 watts. A quick trip to Target later…..and presto! I made coffee out of SUNLIGHT guys! SUNLIGHT!!! It was worth sitting on the floor of a Target trying to find power draw ratings on all their water heaters.
For the TL:DRs
1 – Solar arrays are complicated
2 – Don’t wire just one part of your battery bank in a series – wire the WHOLE THING that way
3 – Check your appliances power ratings to make sure you’re not going to overload your system
4 – Sunlight coffee is awesome
So now our solar array is fully up and running and it’s really cool! We have lots of power to run small things. It’s actually quite an exercise in power conservation to begin thinking about how much power we really need to use on a daily basis – especially when you know it’s limited to the size of your system. But now we are off the grid creating our own power and it feels awesome!
Please comment below with any questions you have about our solar power system and I’ll try to answer them! If you know something I don’t about these systems comment below as well – I’m always up for learning more!