A gentle introduction to solar

This page is a basic overview of solar power for beginner nomads. There are oversimplifications and concepts skipped for clarity; click on the links for more information on a topic.

If you would like a refresher on basic electronics, see the AltE Intro to Electronics for solar video.

• Making some power from solar is easy.
  • Making sufficient power from solar alone to cover your daily power needs is much harder.
  • Making sufficient power from solar alone to cover your daily power needs in all conditions, seasons, and locations is so difficult and expensive that few attempt it; instead we augment solar with other forms of charging.
• panels rarely make their rated output under real conditions
• your location will have a huge effect on solar harvest
• time of year will have a huge effect on solar harvest
• shade on the panels will clobber output
• panels still make some power under cloudy skies

about this summary

Solar power is silent, works for decades, and is always working when the sun is shining.³⁾ It can recharge your batteries and run your loads.

Solar is nearly mandatory for charging lead-chemistry batteries off-grid, since those require of many hours of charging.⁴⁾ Failure to charge lead batteries⁵⁾ fully and regularly leads to battery murder. Solar helps prevent battery murder and the resulting $$ battery replacements.

For people who can control their power consumption, even a small amount of solar can greatly extend time off-grid and can make a huge difference in quality of life.

Solar is not a magic bullet; it is a compromise like anything else. Solar has very high startup costs for the amount of power you get out of it. It could cost several thousand dollars to get the same amount of reliable power one might might get from a residential (or campsite) outlet with a $20 extension cord. Over time, though, the power is “free”.

Getting some power from solar is easy. Getting reliable power from solar alone is challenging (and expensive) because solar harvest is greatly affected by real-world conditions: latitude, season, shade, temperature, even battery voltage. It's bit harsh but you need to hear it early on: you won't be getting 100w out of a 100w panel, and you won't be getting it for 8 hours a day. A crude rule of thumb might be meaningful solar harvest is possible only when the sun is throwing well-defined shadows on the ground.

Solar must not be shaded; not by weeds on the the ground or by other objects on the roof. The panel needs to be the tallest object in the general area.

Alternator charging helps address these shortcomings of solar charging (and vice versa) so it is a common combination.

Solar power uses solar panels to convert sunlight into electricity. This electricity goes into solar charge controller, which keeps the battery optimally charged⁶⁾ and powers any loads (things that consume power). The controller extracts the precise amount of power your batteries+loads demand and no more: in effect the controller is pulling rather than the panels pushing.

Overall it is arranged like this:

  panels -> controller -> battery bank -> loads

Excess power⁷⁾ is stored up in a deep-cycle "house" battery during daylight⁸⁾ and the power is pulled back out at night. The house battery is electrically separate from the vehicle's starter battery.⁹⁾ In broad terms…

“Think of the batteries as a bucket of electricity. It's possible to pour water from multiple sources into a bucket at the same time, and also to do that while water is leaking out of the bucket.” – MarkSF¹⁰⁾

Battery charging is a topic unto itself, and improper charging can kill batteries prematurely.

Since it looks like magic, beginners tend to worry about whether or not their system is working. The solar setup is usually working as intended, and over time you will begin to learn how your system behaves. In the beginning you may watch it constantly¹¹⁾ then eventually need to check “the gauges” less and less often. At some point you will be able to predict what the system is doing before looking.

Since reliable power by solar alone is tough, there are a few approaches to consider:

• best-effort power - you take what you can get from the sun and minimize power consumption to make do. No household appliances, at least not often.
• reliable power - you need power to keep insulin refrigerated, keep working remotely, keep your external heart bypass machine running, whatever. Prepare yourself for added complexity and/or cost because now you have to worry about harvest under poor solar conditions.
  • massive solar - You can still collect usable solar power under very poor conditions if you have a huge amount of panel. This may require “maxxing out” your roofspace, tilting the panels, or deploying additional portable panels. Such configurations may be 1000w or more. One of the pleasant side effects of massive solar is that having enough panel to meet needs in poor solar conditions means lots of bonus power in normal and good conditions. You may be able to run non-essential loads without affecting your battery bank's state of charge.
  • solar + other forms of charging - Solar can work much better when augmented by additional sources of charging. It can work so well that less solar might be required and overall cost reduced.

Pro

• can be set in sun while vehicle is in shade
• can add more power when mounted panels are insufficient
• can be tilted easily

Con

• panels made to be portable tend to be expensive per-watt.
• they have to be deployed in order to work

On the last point: many people believe they will set out their portables any time they are stopped; far fewer actually do it. And even if they set them out they are sometimes placed in shade or facing away from the sun. We must pay attention; solar is unforgiving.

Flex panels are very expensive by the watt. They are a great fit for people who need to mount on a curved surface (boat hull, teardrop trailer, etc) or store/lift a portable.

Otherwise framed panels are the standard for many good reasons.

This question usually means “how much power do I need?” and involves making power¹²⁾, storing power¹³⁾, and using power¹⁴⁾. Unfortunately, you are the only person who knows how much power you will need, and even you may not know yet. Strangers on the internet cannot tell you how much power you need anymore than they can tell you who to date or how many kids to have.

It's not fun but the first step in getting solar is to assess your daily power requirements. Until they sit down to do the math first-timers often have radically unrealistic ideas about power in the campervan. You probably won't be able to run a hair dryer, electric space heater, air conditioner, instant pot, or other high-wattage loads from solar.

Note: you can get a ballpark idea before crunching your own numbers by reviewing some existing solar installs.

Power requirements are calculated daily because the solar feeds the batteries¹⁵⁾ only in daylight. Then at night the system pulls power back out of the batteries. This is natural rhythm of a solar-powered system and the reason why deep-cycle batteries are used.

A minimal solar configuration will

• meet your daytime needs
• then get you through the night without running out of power or overdischarging the battery
• meet your needs again the next day while also recharging the battery

People who are off-grid for longer stretches will also have to think about reserve power. It's not so much an issue for recreational campers who will likely camp only in good weather, and can return home to charge in any case.

In order from traditional to more recent approaches

DIY (do it yourself) means selecting component components individually (panels, solar charge controllers, batteries, inverters, isolators, etc) and installing them yourself.

Pro: Typically lowest cost. Components precisely meet your specific needs. You know where everything is, what it does, and how to replace it if it fails.

Con: Time-consuming. You have to learn enough to pick components and install them.

Kits are usually solar panels, charge controllers, and perhaps related hardware sold in one (hopefully) well-matched package. You will typically need to add your own battery, inverter, etc, as needed.

Pro: some of the product selection is outsourced for you

Con: likely could get better quality and better-matched components for less money with DIY. Packages are often put together by marketing teams instead of engineering or support teams and sometimes the combinations don't work as well as they could.

Often called solar generators, these devices are neither solar nor generators. They are all-in-one systems packaging a battery, an inverter, DC outputs, and allowing various forms of charging.¹⁶⁾

Pro: all of the product selection is outsourced for you. Portable and generally attractive package.

Con: very expensive for what you get, and what you get is someone else's idea of what you should want. Generally not repairable by the end user. People with heavier power needs may find SGs challenging to intergrate into camper wiring.

RVs that are sold as “solar ready” typically have a connector and wiring from Zamp. It is more apt to call it “Zamp solar kit ready” as normal panels cannot be attached to the Zamp port. Here is Zamp's description of Solar Ready, which uses panels with built-in controllers.

It is been judged harshly by some users:

“Solar Ready” doesn’t mean sh*t. It means there is a plug wired to your battery and oh by the way IT IS WIRED EXACTLY BACKWARDS. The polarity on the Zamp SAE style connector is reversed. – John's Tech Blog¹⁷⁾

It is common to mount framed panels on a rack. This accomplishes a few things:

• allows the panels to always be deployed
• where they won't fall over, walk off, or be urinated on by loose dogs
• allows underside cooling to minimize heat-related losses and re-radiation from superheated panels into the van interior
• to keep from drilling extra holes in the roof. Some vans have rack mountpoints built in and don't require any holes for mounting the rack.
• at least one hole will be required for solar panel wiring entry; this is typically routed through a weatherproof cable gland.
• allow changes later; drill new holes in the rack instead of in the roof

Note: avoid racks with “ladder retainers” or other vertical elements. Partial shading is brutal on solar harvest, and carrying around your own shade is an “unforced error”. If you have inherited a rack with uprights consider cutting them off. If you can't cut them off mount the panels as far away from the uprights as possible. If you have a basket the panels need to be on top of (or flush with) the basket instead down inside it.

One of the challenges of learning solar is that until you understand how it works it can be difficult to be confident that it does work.

This information will help you tell if it's working or not.