“How much solar ya got up there?” is almost always the first question people spit out when they are looking at our bus. And they always seem amazed that we can live off of just a few panels. It really shows how far solar and batteries have come in the last few years. Folks building their busses are also often shocked (hehe see what i did there) when they begin pricing out components for their electrical systems. I’ll start by writing up what I did and end with some more explanation if you are completely new to solar.
The answer to “how much solar ya got up there” is 1060 watts. I found a guy selling solar panels out of his backyard. He was a solar installer, bought the panels in bulk, and sold some on the side for a slight discount. I found him on facebook market and got four 265watt polycrystalline Qcell panels for 500 dollars. At the time of writing this, 50 cents per watt is a decent deal. If i were to do it again, I’d really try to find some 400 watt panels- you really can’t have too much solar when living off grid with a family. The panels are 24 volts (actually put out more like 32v) and max out around 8 amps each. A friend gave me a 12 volt marine inverter/charger so that set the voltage I would use for the house battery banks. I made two pairs of series panels then parallelled the pairs so the wires are actually carrying around 64 volts/16amps in peak sun. I used some 12g chord I had lying around to connect the panels to the solar controller. I bought a Victron 70/150 mppt solar controller to step down the panels 65 volts to the 12 volt battery bank/ inverter system. The controller I bought was a little bigger than I needed but I wanted room to upgrade the panels.
Inverters are often a big chunk of the solar budget. Luckly, a friend gave me a12v 3500 watt inverter /charger. Depending on what you plan to run with your inverter you might be able to get away with a smaller inverter but for a large fridge/instant pot/electric kettle/any power tools you probably want something 3k watts or bigger. As far as pure sine wave vs modified sine wave inverters- pure sine wave is more expensive but after some digging it seems like pure sine wave inverters still produce choppy wave forms the resolution is just better. Modified sign wave inverters produce very choppy waves but will work for most anything you need. There might be some medical equipment and sensitive audio equipment that wouldn't work but for everything else, it should work fine. Almost all electronics transform the electricity back down to satisfy their needs anyway. But again- i don't have a modified sine wave inverter so I can't tell you from experience.
Next we have the battery bank. There are numerous different calculators all over the internet to help you figure out what size battery bank you need. There are also a whole army of people to tell you lithium batteries are completely necessary. I am not one of them. Lithium batteries are great if you have the money and/or can’t spare the weight but regular old(cheap) lead acid batteries work fine ( and don’t explode). A couple companies make some great Lithium batteries and they seem like they work great but the price tag is painful. Expect to spend a couple thousand dollars on a lithium battery bank. Lead acid batteries are around a tenth of the price for the some capacity ( and more easily recyclable than a lithium battery). It’s true that Li batteries charge faster and supposedly can be run down close to 0% without many ill effects but you could buy new flooded batteries every year for cheaper than a Li bank. ( I am currently available to shill any Li battery companies products ehhmmm battleborn ehhmmm...). Anyway i have a 250 ah at 12v battery bank in my rig and it works just fine. It keeps the fridge and freezer plenty cold, I can boil water in the morning, and the electric water heater works great in the middle of a sunny day.
The rest of the system is basically switches and breakers. The inverter has two different 120 circuits that go into a breaker box. The 12 volt goes to a block with fuses. I have a couple rotary switches to isolate the inverter and battery bank from the system. Everything runs fairly smoothly. Oh and the victron controller has a nice bluetooth connection to check it with a phone. So far I’ve peaked at 1000 w from the solar system.
The panels I got are grid-tie panels which means they are meant to be attached to a house and not to a bus but so far they have held up great even when driving down the highway.
Now for a little nitty gritty details of a few things that need to be decided for a solar system.
Now for some more nitty gritty to hopefully help anyone that is new to solar and feeling overwhelmed.
The solar panels take energy from the sun and turn it into useable electricity. Depending on how they are designed and manufactured, they produce electricity in 12v or 24v. The panels should say their specs around where the wire come out. When something is called 12v or 24v it actually produced more power than that. A charged 12v battery will be around 13v so the panels need to produce more than 13v to get the battery up to charged. You can
Quick cheat for connecting solar panels together- series panels doubles volts, amps stay the same, parallel doubles amps, volts stay the same. For the most part higher voltages can pass through small wires, higher amps cant.
The solar controller controls the energy coming from the solar panels into the batteries/inverter. There are two types of solar controllers, PWM and MPPT. PWM are cheaper and require your panels and battery bank to share the same voltage. MPPT are much more expensive but they can pair different voltages of panels and batteries. MPPT controllers are also more efficient and will ultimately give you the maximum power from your panels.
The solar panels, solar controller and batteries all work on DC power. Most household stuff we use uses AC power. To change the DC power into AC power you need an inverter- it make the flat power wavy. The inverters are measured in output watts.
A few companies make all in one options for inverter/charger/controller units- some even have integrated batteries. They might be the best option for some people but i prefer to shit it together for the cheapest option. As always if you have a problem, please don’t contact me.
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