** Last Edited 11/12/2012 **
Not sure if you knew this, but the unit for measuring the buttery-ness of your van steeze is Watts. That’s right, A good Solar setup can be the hot knife that spreads the butter all over your steeze-toast, and I’d like to talk about mine in detail. It’s not the steeziest of PV systems, but my steeze-toast ain’t dry either..
“PV” stands for “photovoltaics,” which is a method of creating electricity from solar radiation. It’s far more complicated than i’m gonna pretend to understand.. semi-conductors and shit.. “Science. It works, bitches.”
I’ve been using solar panels as a primary source of electricity for almost 7 years now, so when I built my van last September I had a good idea of what I wanted. If you’re just starting out, and you don’t really have your head wrapped around the idea of PV yet, you gotta dive in and swim around a little. Starter systems are super cheap. Start small. It takes a few years to understand the conservatism of using a PV system, and to understand what your personal energy demands are. (You can’t just plug your computer in and leave it all day.) You’ll learn to check the wattage of devices before buying them, and after a few years you’ll truly know how much electricity you use on a daily basis. Computer + Phone + Camera + Electric Razor + Fridge + fan DOES NOT EQUAL your energy needs. plug them all in at once, and if your inverter can handle it, your batteries will die quickly.
Political Aside: It’s kinda funny how off-grid/environmental people, who are largely left-leaning liberals, are far more skilled at living conservatively. how much energy does Rush Limbaugh use daily, I wonder??
OK, It gets a little dry here. The normal reader might wanna stop reading now. There’s gonna be a lot of numbers. Discussion of Volts, Amps and Watts. Details of my system below:
- 3 110AH 12V AGM Batteries (connected Parallel)
- 2 600W pure sine wave inverters
- 25A charge controller (with shunt and display panel)
- 210W 12V Solar Panel
- 10A – 3 stage Microprocessor Controlled Battery Charger
A PV system is only as good as the batteries. Once you know how much energy you use (ideally with some buffer) you’ll know how many batteries you need. Amp Hour (AH) ratings on batteries are usually rated for 20 hours (but you should check). A 110AH battery at full charge has 110 Amps available over a 20 hour period. So it will output 5.5A for 20 hours (110÷20=5.5). There are many different kinds of batteries, and I’m using AGM (Absorption Glass Mat) for 2 reasons. First, They don’t off-gas, so I didn’t need to make an air-tight box with vents to the outside of the van, and second, they have a longer shelf-life than both Gel, and lead acid batteries.
A lot of people use 6V batteries. You get more amp-hours for the space the batteries take up. Attach the batteries in a series circuit to make 12V at half the AH, I.E. 2 220AH 6V batteries in series is 220AH @ 12V.
A good rule of thumb when building a solar system is to try to get a 1:1 ratio, amp hours Vs. solar wattage. I’m a little battery heavy at 330AH Battery:210W Solar, but i make up for the lack of solar gain in other ways..
Either way, the whole system is 12V DC and a lot of modern appliances are 120V AC. To invert DC to AC I have 2 600W pure sine wave inverters. The first is attached to the 3 110AH 12V AGM Batteries (connected Parallel). If i need to plug in any of my appliances, I turn this inverter on. Computer, phone, etc. Any time i need it. The second inverter is wired into the chassis battery under the hood of the van. I only turn this inverter on when the van is running; this inverter runs on diesel. The 10A – 3 stage Microprocessor Controlled Battery Charger is permanently plugged into the diesel inverter, and permanently wired to charge the 3 110AH 12V AGM Batteries (connected Parallel). If the diesel inverter is on, and the batteries are reading lower than 13.2V the engine/charger will charge up the batteries. Also, in a pinch I can use the van as a generator.
Additionally, mounted on the top of the van is a 210W 12V Solar Panel. I can tilt it up to 54ish degrees either starboard or port. Between the 3 110AH 12V AGM Batteries (connected Parallel) and the 210W 12V Solar Panel i have a 25A charge controller (with shunt and display panel). The controller stops the panel from over charging the batteries, and controls how much amperage to give the batteries based on how full the batteries are. The shunt and display panel tell me lot’s of info about the system like, voltage of the batteries and Amps the batteries are gaining/losing, or how many AH I am from full batteries. The display is handy.
buttery battery steeze. hope this helps someone one day.