Making, storing, and using power wisely is important for happy vandwelling. Power issues can seem overwhelming and confusing; this article intends to lay out the basics. If you would like a refresher on basic electronics, see the AltE Intro to Electronics for solar video.
Before you spend money on making/storing power in your vehicle, be sure to leverage other sources:
It may be useful to carry a gym bag with a power strip, extension cord, and any items that need to be charged. The power strips allows you to charge many things at once, and the extension cord helps you reach faraway outlets or outlets in inconvenient places (on a wall, behind furniture).
There are two generally-separate electrical systems in your vehicle1):
Only you will know that, because only you will know what kinds of electrical loads you need (or want) to run. Unlike a wall socket in a house where you can run pretty much anything you want, using power you make off-grid is a series of choices and compromises. Some things are easy to run off-grid; some things are harder and require more infrastructure, planning, and money. Some things are impractical in campervans. Car-dwelling presents additional power challenges due to limited space and charging methods.
Here are some very general ideas to get you thinking:
Note: devices that have "wall wart adapters" may not require an inverter.
The following is a guide to calculate battery storage and solar needs. Be honest about what loads you want/need to run and how long you plan to run them. You can also check out Far Out Ride's sizing guide and their load calculator if it's more your style. Remember that you can supplement/substitute the solar system with DC-DC charging from your alternator and/or shore power.
A general guide is to have 200w of solar for every 100ah of 12v lithium battery. No one has ever complained about have too much battery capacity or too many solar panels, so rounding up is always a good practice.
(With credit to CMDR_Schrodinger)
Solar panels only operate at “peak capacity” for approximately four to six hours per day. The amount of solar power your panels can capture will depend on the angle of the panels to the sun, cloud cover, temperature, latitude, dust on the panels, etc. The amount of time you'll spend capturing that solar power will depend on latitude, season, weather, etc.
As a general estimate, assuming ideal weather conditions, but worst-case charging time, divide the result of your minimum battery bank capacity by four. This result shows how many total watts of solar you'll require to fully charge your battery bank each day.
The chances of getting the full yield out of your panels are slim to none. In the North American winter, for example, you might only get up to 50% of your panel's rated max wattage even on a clear day.
For a more exact estimate based on time/place, see this article on solar harvest modeling.
An example with a 93% efficient inverter and a 12 volt battery bank (Results are rounded up):
“Perfect conditions” solar array wattage with a four-hour peak sunlight charge time: 912 / 4 = 228 watts of solar panels.
The above calculations are for Lithium batteries; for lead chemistries, you should double both the amp-hour and solar wattage to avoid battery murder.
Most campervans use solar combined with another charging source, usually the van's alternator. This combination can be both cheap and highly effective5)
| Pro | Con | |
|---|---|---|
| shore power (outlet) | cheapest per watt simple abundant power | often not available if available you are tied to the outlet by your cord/adapter campgrounds with outlets are more expensive |
| solar | automatically makes power when the sun shines makes high voltages needed to fully charge lead-acid batteries silent lasts for decades | most expensive per watt can be complex panels are large output drops dramatically when shaded |
| alternator | automatically makes power when driving about 1/10th the cost of solar for the same current output | relatively low charging voltage6) can result in chronic undercharging should not idle to charge most people don't drive enough to fully charge lead-acid |
| alternator (ciggy port) | available on all vehicles | typically limited to 10A (120-150w, see this end-around). |
| generator | can make 1000w+ of 120v can run for days inverter models are quieter | can be expensive ($1000+) maintenance needs to be stored when not in use noisy not allowed in some areas/times |
Alternator & solar charging enhance each other when used together. Adding alternator charging to solar can significantly reduce the amount of solar required to meet your needs.
Note: So-called solar generators do not generate power: they are battery banks, usually AGM or lithium. See below. Wind power is generally impractical for van use.
Power production tends to be heaviest during the day while power use tends to be heaviest overnight. This means power needs to be stored when power is abundant so it can be used later. The most common storage for power is in a deep cycle battery bank, aka “house bank”, “house battery”, or “auxilliary battery”.7)
| Pro | Con | |
|---|---|---|
| Flooded lead-acid (FLA) | cheapest per Ah most tolerant of abuse | lowest current throughput maintenance (“watering”) required can only use 50% of rated capacity8) |
| Sealed lead-acid (SLA, AGM) | able to charge/discharge more current than FLA no maintenance required | more expensive per Ah9) cannot check or replace electrolyte |
| LiFePO4 (LFP) lithium | very close to normal 12v ranges available as “drop-in” replacements for lead-acid current throughput can be more deeply discharged than lead-acid | most expensive upfront per Ah cannot be charged in freezing temperatures |
| Non-LFP lithium | cheaper than LFP per Ah current throughput | thermal runaway voltage not well-suited for 12v systems |
| "solar generators" | convenient | relatively expensive non-repairable designed for generic needs, not your specific needs typically slow to charge typically limited solar input limits and performance |
The battery bank is sized to meet your daily power needs and as well as any extra margin you might like.
Using power is the simplest part. It's so simple the newbie may find themselves overdrawing from the available power. A low voltage disconnect (LVD) is one way to keep from overdischarging the bank.
Although 12v house banks are most common there are use cases where higher bank voltages (24v, 48v, etc) may be desirable:
Challenges: