“Solar for Vanlife 101”

 By Mohit Kaura

Intro to Solar Power

On-board electricity is one of the most essential components of vanlife. While there are several ways to keep your on-board batteries charged, solar charging is the most versatile and eco-friendly option. Unlike the shore power plug-in option, you could be off-grid in the middle of nowhere and still be completely self-sustained. And you don’t have to worry about keeping the van running to charge your batteries. All you need is direct exposure to the sun, and you can have all the power you need. Let’s dive deeper into how solar power works.

Clean, robust and maintenance-free, solar energy is produced directly from sunlight falling on the photovoltaic cells of the solar panel. The electrical charge created in the cell causes electricity to flow, which can be stored in a battery to be used at your convenience.

Basic units and terminology

Current – Ampere (A)

Voltage – Volts (V)

Power/Wattage – Watts (W)

Power = Current X Voltage

So, 1 Watt = 1 Ampere X 1 Volt

Energy Stored in your battery – Watt-hour (Wh) or KiloWatt-Hour (kWh) {{1 kWh = 1000 Wh}}

Current coming straight from the battery – Direct Current (DC, 12 V)

Current coming from the inverter/power strip – Alternating Current (AC, 110 V)

Solar Panels

Monocrystalline and Polycrystalline solar panels are two types of solar panels you’ll come across when shopping with popular brands such as GoPower. While monocrystalline solar panels are more expensive, they can reach over 20 percent efficiency. On the other hand, polycrystalline panels are cheaper, not only is their efficiency limited to 15 to 17 percent, but they also have a shorter lifespan due to lower resistance to light and heat. So, while monocrystalline panels might seem like a heftier initial investment, you will benefit from their higher density that allows for a higher power generation.

Lately, flexible solar panels have been getting popular due to their light weight, ease of install and the ability to adjust to the curvature of certain van roofs. They tend to be more expensive than the traditional mono or poly panels, but most people are not aware that these panels could have significantly lower efficiency ranging from 15 percent to as low as 7 percent. This is also the case with roll-out solar panels mats.

Generally speaking, the bigger the solar panel size is, the bigger their power output will be. So, a 100-Watt panel will almost be smaller than a 200-Watt. Solar panels come in all sorts of different wattages, ranging from as small as 50 Watts to as big as 500 Watts. Using multiple 100-Watt or 200-Watt panels are the most common choice for vanlifers as these panels offer flexibility in the layout design on your roof, should you want to add cargo box or a roof deck. Many people who don’t utilize the roof space for cargo go with one big 300-350 Watt panel, such as myself. 

Batteries

Almost all long-lasting batteries are compatible with solar charging. Most vanlifers prefer one of the more popular options such as lead-acid deep cycled (AGM or Gel), Lithium-Ion (Li-Ion), or Lithium Iron Phosphate (LiFePo) batteries. The sealed lead-acid batteries, though robust, are slowly phasing out due to the superiority of lithium-ion batteries when weight, life-cycles and efficiency are considered.

Lithium-ion batteries, though more expensive, are considerably lighter than lead-acid batteries, and go up to 200-300 cycles compared to 50-100 cycles for a lead-acid battery. The newer tech, Lithium Iron Phosphate (LiFePo) batteries are the lightest in weight and go up to 2000 to 12000 cycles. But, the high price for these batteries deter most buyers from buying these batteries, even though the higher initial investment is completely worth it.

The efficiency of batteries usually increases with voltage system, so a 6V battery system would be the least efficient and is usually employed in a golf cart or small electric vehicles, while a 48V system would be the most efficient, which is why it is used for off-grid homes. However, due to the small scale of a van, most people use 12V batteries and they work just fine for the amount of power one needs in a van. The common battery sizes vanlifers choose range from 100Amp-hours and 200 Amp-hours, with some going big with 300+ Amp-hour battery setups, though 200Amp-hour is sufficient for most vanlife electrical power needs.

Charge Controllers

Solar Panels will put out anywhere between 18V to 40V depending on their type and light sensitivity, which would destroy the 12V battery system. The charge controllers are crucial in ensuring that the battery receives the right current and voltage for its kind.

Charge controllers come in two categories, PWM and MPPT. MPPT chargers, though more expensive, can be up to 92% efficient, which is almost 30% more efficient than PWM controllers. The initial investment into buying the more expensive MPPT charge controller is definitely worth it when it comes to ensuring safe charging and longevity of the batteries.

Wiring Sizes

When wiring all your devices, it is essential that you use the appropriate size of wire to prevent them from melting due to an unexpected current surge. The wiring in the US uses AWG (American Wire Gauge) system. 1 AWG wire is the thickest wire available at hardware stores, and it keeps getting thinner and rated for less current as the number goes higher, as can be read below.

• 14-gauge wire: 15 amps
• 12-gauge wire: 20 amps
• 10-gauge wire: 30 amps
• 8-gauge wire: 40 amps
• 6-gauge wire: 55 amps
• 4-gauge wire: 70 amps
• 3-gauge wire: 85 amps
• 2-gauge wire: 95 amps

 So ideally, you want to use 2 AWG wire for connecting your batteries to each other and to the inverter, 4 AWG wire for connecting the charge controller to the batteries, and 8,10 or 12 AWG wires for lighting and power sockets, depending on what you intend to use with those wires.

Additionally, having circuit breakers and fuses is always recommended, even though the batteries and controllers come with internal fuses.

Power calculations

If you have a device, say a fan, rated for 50 Watts, it will pull 50 watts of power every second.

Let us assume the following are your regularly used devices. The average wattage rating (which is how many watts they consume every second) is mentioned next to them.

Fan – 50 Watts

LED lights – 30Watts (depending on the type/number of bulbs etc)

Charging Phone- 10 Watts

Charging Laptop — 60 Watts to 90 Watts, depending on the size

Charging Camera/Drone batteries – 40 Watts

Small Blender – 70 Watts (Low Setting)-350 Watts (High setting)

Fridge: 60 Watts (For a DC fridge), 250 Watts (AC), which is why most people prefer DC fridges.

Small Microwave- 700Watts

Say, you want to run all of them at the same time. This will result in a total usage of:

50+30+10+70+60+40+700 = 960Watts,

and say you use it all for an hour, it means you’ll use 90Watt*1 hr = 940Watt-hour, which in a 12V system is 940 Watt-hour/12V = 80Amp-hour. More info on these calculations below.

However, not all these devices will run for 24 hours every day, so you can always account for the total power usage by multiplying it with the number of hours you use it every day. For example, using the 50Watt fan for two hours would result in 50Watt* 2hr = 100Watt-hour of power usage.

If you have an inverter rated at 1000Watts, you can theoretically run all the above mentioned appliances without overloading the inverter. But say you run the microwave and the small blender at high speed together, your total usage will be: 700+350 = 1050 Watts, which will trigger an overload and the inverter will shut down. So, in this case, it will be beneficial to have a bigger inverter, say 2000Watts.

Simple mathematics, yeah?

Choosing the size of your solar array

So now, you have the size of your battery and inverter picked out, and now you want to add solar power to recharge your batteries and be a sustainable van-lifing badass.

Choosing the size of your solar array depends on how much and how fast you want to charge your batteries.

Common solar panel arrays that van-lifers use range from 100Watts to 600Watts, depending on their needs and rooftop space availability.

An important factor to consider is that solar panels generally output 75%-80% energy of what is listed, for example, a 100Watt panel will give you 80 Watts on a very sunny day at best.

Know that all days won’t be sunny, so always have extra energy on board. Keeping the battery at least half full at all times can be a lifesaver in bad weather conditions.

Say, you picked out a 200Ah (or 2400Wh), 12V battery and you want to charge it from completely dead to full. Assuming a 100-Watt panel can generate about 80 Watts consistently in direct sun on a clear day,

To charge a 200Ah (or 2400Wh) battery in this case will take 30 hours (80Watts*30hr = 2400Wh), which is clearly too long to wait, especially since you’ll only get 6-8 hours of full sun every day.

An alternate option for a faster charge would be to use a 300Watt panel producing 240 Watts on a clear day will charge your battery from dead to full in 10 hours. (5 hours if it is already half-full and so forth).

Solar Installation

Roof Racks

Many people will install roof rails on their vans, and mount and bolt the panel directly on to the rails. Steel and Aluminum are common choices for roof rails, with aluminum being more durable and lighter, and thereby, more expensive. Some companies will also sell aluminum mounts for solar panels that could be bolted on to the roof, or the roof rack, depending on your needs.

Z-Brackets

Several companies will sell Z-brackets with their solar panels, that could be bolted directly on to the roof, but requires drilling several holes onto the roof. If you opt for this method, be sure to properly seal the holes with an industrial grade, waterproof sealant.

Double-sided tape / Eternabond

For flexible solar panels, one doesn’t have to bolt anything on to the roof. Their lightweight and flexible structure enables the use oof double sided tape on the underside of the panel which can be secured with the industrial grade tape, eternabond. The flexible panels do tend to heat up so it is recommended to use a plastic corrugated sheet under the panel to avoid direct contact with the roof.

 Now that you have a glimpse into the world of vanlife solar energy, we wish you the best of luck in choosing and installing your solar array so you, too can enjoy sustainable and clean energy as you explore the outdoors.