The electrical system is potentially one of the more complicated, intimidating, expensive, and important systems in the conversion process, so I highly highly highly recommend that you start looking into this one early.
It will determine a great many other things about your build that are obvious, such as how many batteries and solar panels you need, as well as things that are less obvious, such as how many options you have for cooking and that the means of cooking you choose will influence kitchen layout and that will impact how you design the rest of your storage space.
How many solar panels you need may also severely limit how many options you have for fan placement, and how much electricity you will have available may determine whether you can have an electrically powered sink pump or if you need to go manual.
Lights (low voltage), fans, laptops and phones should not be a problem for most battery systems, with laptops using by far the most, but a toaster oven or microwave is probably out of the question.
Remember, solar panels heat up and if placed flat against the van roof (e.g. flexible panels) they will transfer their heat to your van, which will heat it up in summer. Stiff panels can be mounted with a breather air space between them and the roof to reduce heat transfer, but there is a trade-off to that, too.
Stiff panels that are elevated need to be bolted very well to the roof, especially on their forward edges, so that they do not come loose over time and come flying off the van at 70mph on the highway and go crashing into the windshield of the car behind you. Mounting them safely is very doable; just something to plan for.
I also painted the roof first with ultra-white reflective paint to refract as much of the sun’s and solar panels’ heat as possible.
Back to the electrical system itself. I decided on a Lithium Iron Phosphate (LiFePO4, LFE) system over AGM batteries. I’m not going to go through all they whys and wherefores because there are a lot of good resources out there already: in short, lithium is superior to led acid in every possible way besides the cost. Technomadia has a good primer on them.
Lithium batteries are still a relatively new technology, however, and balancing them was intimidating me—I spent far too many hours reading about how to do it and still feeling lost—so I decided to go for a self contained battery system rather than piecing it together myself.
There aren’t that many out there yet; I found fewer than a dozen brands and models that would have enough capacity for my 12V fridge, laptop and phone. That’s pretty much all I wanted to be able to power, but did want some extra capacity for the inevitable later decisions to add an electrical device or two.
My battery system:
I’m not going to tell you which battery system I eventually bought, because I have had a number of problems with it and don’t want to give the company a bad reputation before they have a fair chance to correct the issues. I think that in general they have a good product, it just needed a little more testing before being brought to the market, and if they correct those few minor issues, they will have a really good product to sell. So far I will say to their credit that they have given me very good customer service.
I went with Renogy Monocrystalline Solar Panels. Renogy is a good company that makes good photovoltaic (solar panel) products. I figured on 300 watts as a good compromise between planed electricity usage and price, and I can always add another later. Renogy also has some very informative setup videos on how to connect different amounts of panels in series and parallel.
I have been very happy with these. So far they have been in pounding rain, minor hail, high winds, snow, heat, and don’t have a scratch on them. They have performed admirably, even picking up a very little charge under street lights as I drive by.
I got a Luci Lux – inflatable solar light and loved it so much I got a second. They are small, lightweight and durable, and plenty bright, even on low. In the morning I put mine in a window or outside to collect sunlight all day, then I have plenty of light at night to read or write by.
A major benefit is that it doesn’t use my electrical system’s energy at all. It gives me free light, every night, leaving my solar generated electricity to power other things.
Once the fall started getting close to winter, I was looking for a way to stay warm at night, and propane wasn’t an option.
This was the inevitable additional electrical device that I am glad I preplanned for early on. I’ve had enough electrical capacity to run it whenever I needed it.