Supplying electricity to your dwelling

Living on the road and off the grid doesn’t mean you have to forego the conveniences of modern technology. Most of the electronics and appliances in the home are available in smaller packages suitable for use in a car or camper situation. But be warned: Setting everything up will be more complex than just unboxing and plugging in. Fortunately, it is possible to start small and build up to a complete electrical system, learning as you go.

DC versus AC power

The big transition you will have to make is from an AC power source to DC. Home-oriented appliances are plugged into an alternating current (AC) source, while battery systems supply direct current (DC). Whenever possible, try to buy electrical devices that run directly on DC. These will avoid energy losses, as no conversion is needed. DC appliances are often branded as “camping” this-or-that, and they usually require 12 volts (the same as a car battery).

Although DC appliances are ideal, the market for them is smaller, so they often cost more than their AC brethren – possibly more than they save in electricity. Always do the math and watch for deals. It is not uncommon to remain with AC devices, which will need an inverter to convert the battery’s DC to AC.

When buying an inverter, pay attention to whether it is a pure or modified sine wave inverter. Modified sine wave inverters cost less but can cause problems with devices and power tools that depend on the characteristics of a stable sine wave signal.

Your first inverter could very well be one that plugs into the car’s “cigarette lighter” socket. These inverters are usually rated 400 to 800 watts, which is laughable. Anything more than 120-180 watts (10-15 amps) will blow a fuse to prevent a fire. The socket can charge a phone or small laptop, but you won’t be running a 400-watt coffee maker.

Batteries

The heart of your power system is the battery bank. Avoid the temptation to use your vehicle’s lead-acid battery for powering electronics or charging devices. These batteries are designed to provide a quick burst of power for starting the engine and then be quickly topped off by the alternator. Regularly discharging your starter battery is a great way to send it to an early grave, possibly leaving you stranded.

The most sensible choice for electricity within the vehicle is a sealed “deep cycle” type of marine battery, although lithium batteries are gradually becoming more affordable. Note that these, too, are not supposed to be completely discharged. Recharge your battery whenever it falls below 50% capacity, and draw power from a different battery while the first one charges.

Yes, this means you should have at least two batteries, and each one should be rated for double the capacity that you intend to use. Over time you may add extra batteries to each bank.

Batteries add weight to your vehicle and consequently reduce your mileage. It’s really a balancing act between convenience and fuel efficiency. If you will be driving a lot, consider a smaller battery bank that can be charged by the alternator. If you plan to remain parked as much as possible, a larger battery bank will help you endure cloudy days without having to run the vehicle.

Batteries can pose an explosion hazard while charging. Check, double-check, and verify that your charging system will automatically shut down when the batteries are fully charged. Also provide adequate ventilation while charging. Hydrogen molecules are good little escape artists, but there is still a significant risk of ignition if you allow hydrogen to build up in a confined space faster than it can escape.

Going solar

Over the past few years, solar panels have emerged as a viable option. However, they still involve a significant up-front investment and demand some technical ability to install. What you will need:

  • Solar panel(s)
  • Charge controller
  • Battery
  • Wiring and conduits

50 to 100 watts should be enough to maintain a cell phone and perhaps a tablet computer. With 100 to 200 watts, you can also power a small, efficient laptop for a few hours a day. 200 to 400 watts is enough to keep a small fridge cold (at least part-time) and run a larger TV or computer monitor for a couple hours a day. Above 400 watts and with a large battery bank, you can power almost anything that you would run in a house–just not all day and not at the same time.

Solar charge controllers

There are two main categories of charge controllers: PWM and MPPT. PWM charge controllers are less expensive but also less effective than MPPT. The PWM controller will try to apply the appropriate voltage to a battery, depending on the current status of the battery. When the voltage from the solar panels closely matches the necessary voltage for the battery, PWM works great. However, if the solar panel voltage is too high, the excess becomes waste heat.

An MPPT charge controller works more efficiently than PWM. That is, more total electricity reaches your battery by providing a better match between the optimum voltages of the solar panel and battery. The drawback, as usual, is that MPPT charge controllers are significantly more expensive than their PWM counterparts. The efficiency gains may not offset the difference in price with small solar installations.


 MENU