Road Trip Survival Guide – Electrical Power

This entry is a part of a series. Check out the rest of the Road Trip Survival Guide for more valuable information.

Technical, Technically

I don’t want this Survival Guide to be overly-technical. My purpose is to broaden your mind by giving you ideas you might not have thought of. Not to micromanage your trip or to give a lecture on electrical physics. But in preparing for my trip last year, I learned a lot when researching solar power. It would be an opportunity wasted not to summarize that research and share it with you.

But before we continue, please review the scopes and perspectives that I’ll be addressing each of the questions presented in the Road Trip Survival Guide.

It All Starts with Conservation

Like drawing water from a faucet, plugging into a power outlet at home is so easy and cheap that we hardly ever think about it. On the road, you don’t have ready access to a power outlet. And while finding electricity on the road isn’t necessarily difficult, you will find it either inconvenient or expensive (or both), no matter which option you take.

PowerTherefore, I recommend weeding as many electrical devices out of your luggage as possible. The fewer devices you have to plug in or recharge, the better. For most of the trips I take, that boils down to one single device: my cell phone.

My outlook on electronic devices has evolved over the years. I was irritated by what I called “Swiss Army Devices”. So many electronic devices were being manufactured with multi-functionality that it became difficult to tell them apart. My cell phone could act as an iPod, laptop, wristwatch, camera, GPS unit, flashlight, and probably a dozen more devices I’m not thinking of. (Oh, and a phone!) Some of those devices had themselves evolved multi-functionality as cell phones had. At the time, I preferred single-function devices that performed one job very well.

But now, as a minimalist traveler, I embrace my Swiss Army cell phone. Its multi-functionality means I can carry less cargo and have fewer devices to power or recharge. Of course, since I’m putting all of my eggs in one basket, I am screwed if anything should happen to my cell phone. So I try to have some form of backup for the most critical functions. I will usually bring maps or printed directions, a separate flashlight, and a notebook and pen.

If you decide to go on your road trip with absolutely no electric or electronic devices, congratulations! You get to skip the entire rest of this article. But for those of us who can’t quite part with our cell phone, laptop, or mini-fridge, let’s talk about how to get electrical power on the road.

Your Car’s Electrical System

The most obvious source of power comes from your vehicle. Most vehicles come with at least one cigarette lighter port from which you can draw power with the right adapter. Newer vehicles are being produced with multiple lighter ports, USB ports, and even AC outlets.

Assuming that you just have a cigarette lighter, all you need is a simple adapter to convert the battery’s 12V of direct current (DC) into the 110V of alternating current (AC) that most devices and appliances use. You can get higher-end adapters that have multiple outlets and USB ports. Or, you can simply buy a power strip to turn one outlet into 6 or more.

The important thing, however, is to rely on your car’s battery only while the vehicle is running. If you use your car’s electrical power when it is not running for too long, you might not have enough power in the battery to start your vehicle. How long is too long? It depends on how much power you’re drawing from the battery.

Your car’s battery is its energy source to power the ignition system. Once your car is running, your fuel-powered combustion engine takes over and produces energy. This energy the fuel generates produces (a) kinetic energy to power the engine, (b) recharges the battery for the next ignition, and (c) provides power for various electrical systems within the vehicle. Without the battery, the combustion system can’t start. So it’s important that you preserve your battery power and only draw electricity from it while the vehicle is running and recharging the battery.

Is your car’s electrical system enough to power your devices? That depends. How much do you intend to drive each day? How much power do you need? If you only drive for an hour a day, you’re not going to be able to do much more than recharge a cell phone, if that. If your drive for 4, 8, or 12 hours a day, then you can recharge just about any electronic device. But if you need something to be drawing electricity 24 hours a day – such as a small refrigerator – then you either need to drive 24 hours a day or find some other source of power.

Taking Care of Your Car Battery

For most road trips, your car’s battery should be enough to sustain you. But take two basic tools with you: a jumper cables and a multimeter. You should be able to find either one for about $20 or less.

Use the multimeter to periodically check your battery’s voltage. Do this especially if you hear strange noises during ignition or if you notice unusual readings on your dashboard. To use a multimeter, turn off your vehicle and pop open the hood. Turn the multimeter on and make sure that it is set to read DC voltage. Touch the black probe to the negative battery terminal and the red probe to the positive battery terminal. A healthy battery at rest should yield a reading of about 12.6V. Anything below 12.4V is indicative of an unhealthy battery.

If your battery is too low to start the ignition system, you may need to rely on another vehicle to provide a jump. To jump-start your car, make sure both vehicles (donor and recipient) are turned off and not in direct contact. Connect a red clamp to the dead battery’s positive terminal. Connect the other red clamp to the donor battery’s positive terminal. On that same end of the cable, connect the black clamp to the donor battery’s negative terminal. Connect the final black clamp to a clean, metal surface of the dead vehicle – away from the battery, gas fumes, fans, or belts. Start the donor vehicle and allow it to run for about 5 minutes. Then start the recipient vehicle. Disconnect the cable clamps in reverse order and take your vehicle in for service.

Other Energy Sources

You might find opportunities to charge your devices indoors. Libraries, restaurants, cafés, pubs, highway rest areas, and other public spaces frequently have outlets that you can plug into. Some business owners might not permit you to siphon off their power. Others will permit it if you ask nicely. Others (especially Internet cafés) encourage it by having clearly-marked outlets near or embedded in your table. Of course, in a restaurant, pub, or café, you should order something while you wait for your device(s) to charge.

Consider how many devices you need to recharge. Waltzing into a restaurant with a dozen devices under your arms is likely to get you kicked out. On the other hand, I’ve been in libraries that have outlets installed in private study cubbyholes. You can discreetly carry in a backpack of devices and plug them all in while you read a book. Just remember to bring a power strip if you’re charging multiple items.

Many public buildings – especially in large cities – are installing dedicated recharge stations. As time goes on, they may become more prolific in smaller cities. I’ve also seen recharge stations outdoors, near traffic intersections. But I can’t imagine how convenient it could possibly be to stand tethered to a street corner like that. It makes more sense to do it indoors where you can have a drink, snack, or read a book while you’re waiting for your devices to recharge.

Solar Power Systems

If you need something plugged into electricity 24 hours a day (like a refrigerator), you might consider installing an independent power system in your vehicle. The most common system is solar power, and that’s what I’ll be discussing here. But wind power systems are also available.

I am a huge advocate of developing solar powered energy. The sun is 333,000 times the size of the Earth by mass, and 1.3 million Earths could fit inside it by volume. For all that mass and volume, our star is nothing but a giant nuclear fusion reactor that pumps out 3,846,000,000,000,000,000,000,000,000 watts of energy, of which about 174,000,000,000,000,000 watts strike the surface of our planet. That’s a ton of energy, and we harness so little of it. We are squandering great potential.

I am not a huge fan, however, of current solar technology. Solar panels take up a lot of surface area, the batteries required to store the energy are heavy, and the systems are expensive.

Installing a solar power system in your home makes sense. Roofs have plenty of surface area for mounting solar panels. Battery weight is pretty irrelevant. And if solar power can take your household completely off the grid, then the installation investment is well worth the long-term savings.

But vehicles don’t have as much surface area for mounting solar panels. Heavy batteries take up valuable cargo space and weigh down the vehicle, reducing its fuel efficiency. And given the limits of what a vehicular solar power system can do, it’s unlikely to be cost-efficient.

Solar Power

For many weeks last year, I considered installing a solar power system on top of my camper van. (Given that my van died just two days into my road trip, I am grateful that I did not make this investment.)  At the time, I was considering a small refrigerator, a portable stove, a fan, and a space heater, plus electronic devices. When I calculated the power consumption, system requirements, and costs, the system became impractical. When I eliminated the larger appliances (which had greater utility value than the electronic devices), I discovered that although I could dramatically reduce my power consumption, the overall price of the system didn’t decrease by very much. So an expensive project became a slightly-less-but-still expensive project with considerably less value. So I ditched the electrical appliances and relied upon my car’s battery for my electronics.

If more power can be harnessed with a smaller surface area, if the batteries can be made lighter, and if the overall technology gets cheaper, then solar power systems will make a much better alternatives for more people.

Designing a Solar Power System

So you think a solar system might be necessary for you. Let’s discuss calculating your power needs and designing a system. First, get used to prefix conversions, otherwise you’ll end up making exponential miscalculations. To guide you through the planning process, I’ll be referencing a plan to charge a cell phone, laptop, fan, and portable stove.

I am not an expert electrician or even an expert mathematician. I’ve done a lot of research on this, so I’m pretty confident in my numbers. But if I’ve gotten anything below wrong – please let me know.

The analysis begins by determining how much power you will consume. All of your electric and electronic devices will have technical specifications and power consumption ratings printed somewhere. For most electronics (cell phones, laptops, etc.), you’ll find these printed on the device’s power adapter. Devices with ordinary plugs (like a fan) will have their information printed on the device itself, since the plug isn’t big enough to print information on. Other devices – like string lights – are too tiny to print on, so you’ll find their information printed on the box they’re sold in.

My cell phone draws 14.4 watts. My laptop draws 65 watts. The fan draws 72 watts. And the stove draws 900 watts.

Next, determine how many hours a day you’ll power each device. My cell phone usually sits on the charger while I sleep. I’ve never clocked its minimum recharge time, but I can count on it needing another 2-4 hours during the day on the charger. So we’ll set that at 12 hours to be on the safe side. I probably won’t use the laptop for more than 2 hours a day. Since my car provides air conditioning, I only need the fan on overnight. I don’t need to cook breakfast, but I may want to use the stove for one hour each day to cook supper. So we multiply the wattage of each device by the number of hours they’ll be plugged in. I calculate 1,778.8 (or about 1.8kWh (kilowatt hours)) per day.

Next, we’ll use a handy online tool provided by Renogy (a solar system vendor) to calculate the rest. Click here for the calculator. (It should automatically open up to the off-grid solar sizing calculator. If not, make the appropriate selections to get to the right calculator.)

The calculator asks you for wattage and hours separately. The reason I calculated watt-hours earlier on my own is because I’m not using each device for the same number of hours per day. So what I’m going to do here is input my total watts above (1,800) and insert “1” for the number of hours. The answer will come out the same.

For controller efficiency, select either 80% or 92%. You can evaluate the pros, cons, and costs of a PWM or MPPT controller on your own – I’m not getting into that much technical detail here. I’m choosing MPPT for this example.

Next, you have to determine how many hours a day your solar panels can draw energy from the sun and charge your batteries. There are three main factors that determine sun hours: geographic latitude, time of year, and weather.

Check out the Daylight Hours Explorer (requires a Flash player). At the equator, you are guaranteed 12 hours of daylight every day, all year long. As you move away from the equator, daylight hours will increase above 12 hours as you approach one solstice, and decrease below 12 hours as you approach the other, always crossing 12 hours at the two equinoxes. At or above 66.6° latitude (north or south), you will have days centered around the solstices when you have 24 hours of daylight in one season and 0 hours of daylight in the opposite season. At the north and south poles (90° latitude), you experience 6 months of nonstop daylight followed by 6 months of night.

Look at your planned route and identify the locations where you will be closest to and furthest away from the equator (your northernmost and southernmost points, if you’re not crossing hemispheres). Determine those lines of latitude. For my example, I’ll use Jasper Alberta and Big Bend National Park – about 53°N and 29°N. Since both of these places are in the northern hemisphere, I will find the lowest number of sun-hours to be at the winter solstice.

Since I don’t like the cold, I don’t want to travel in December. I’m going to travel in the summer instead – say between June 1 and September 15. Again, since I’m in the northern hemisphere, my least amount of daylight occurs when I’m closest to the winter solstice, so September 15.

According to the map, I get about 12.8 hours of daylight in Jasper in mid September. In Texas, I get 12.2. So for our purposes, we’ll round down to 12 hours. And that’s not an uncommon result. Since any location’s annual daylight will averages to precisely 12 hours, any trip of extended duration spanning great distances will likely result in minimum sun-hours being close to 12.

Now I have to factor in cloud cover, which is unpredictable. You’re going to weather the weather (pun intended) via your battery capacity. But you don’t want to drain your batteries every day. So instead of counting on 12 hours of sunlight, I suggest slashing your sun hours in half.

So for this system, I’m being told to to get a 326 watt system. I can use 12V batteries rated at 300 amp-hours (Ah) or 24V batteries rated at 150Ah. Watts = Volts x Amps, so either one results in 3.6 kilowatt-hours (kWh).

Now let’s translate all of this into equipment.

Batteries: Let’s use the 300Ah 12V batteries for this example. I’m going to purchase 4 of them and split them into two pairs of two. Each pair of two will be wired in series, which will increase the voltage but not the amperage. So each pair of four batteries will yield 300Ah at 24V. Next, I’ll tie the two pair together in parallel, which will increase the amperage, but not the voltage. This will yield 600Ah at 24V, or 14.4kWh. This is enough power to run everything for 8 days (remember I’m using 1.8 kWh per day). The odds of me going 8 days without sunlight are pretty slim. But I don’t want to drain the batteries too low, either. Having 8 days of reserve and counting on sunlight at least every other day should mean (hopefully) never dipping down below 75% battery capacity.

Solar Panels: Most solar panels built for mounting on surfaces like a car roof will be rated somewhere between 100 and 300 watts, with the higher wattage panels naturally being more expensive. At 6 hours of average daily sunlight, I’m going to want 300 watts worth of solar panel to offset the 1,800 watts of energy I’m consuming each day.

Charge Controller: I’m not going to go into detail about charge controllers, except to explain what they do and why the system needs one. Charge controllers manage how much power is delivered from the solar panels to the batteries to prevent over-charging and draining. Commercial controllers usually include digital displays so you can monitor your overall power system.

Inverter: Like the adapter you use in a cigarette lighter port, a power inverter is necessary for your solar power system to convert DC from the solar panels and batteries into AC for your devices. You’ll need an inverter strong enough to handle the total amount of power you will consume in any given moment. So in my case, the cell phone, laptop, and fan are likely to be running/charging  simultaneously overnight, but their total power consumption of 150 watts is dwarfed by stove’s 900 watts. With a 900 watt inverter, I can’t run anything else while I’m running the stove. If I have a 1000 watt inverter, I can run the stove and charge at least one other device, but not all three. With a 1500 watt inverter, I can run anything at any time.

Emergency Power Sources

A full solar power system might not be economical for your power needs, but a handheld solar cell isn’t a bad idea to have along if you’re out hiking in the wilderness and nowhere near a power outlet.

Alternatively, you might consider a hand-cranked flashlight or lantern. Even if you don’t need the light, many models include charging ports so you can use the power you’ve cranked into its batteries to charge other devices.

Foreign Adapters

If your road trip is confined to North America, then the standard three prong outlets are all that you will encounter. But overseas, you will encounter different outlet requirements.

There are five major types of outlets. Two of them cover most of the global map, but Australia, India, China, and the United Kingdom represent the most-visited countries that incorporate the other three. A universal adapter can be procured for between $25-$50.

Make sure that any adapter kit you purchase also includes a power converter. While outlets in North America run at 110V, most of the rest of the world runs at 220V. You will fry your devices if you use an adapter without a converter.

Other Ideas?

Have I missed anything? How do you find and manage power? How do you conserve power? Do you have questions? Do none of these solutions work for you because of specific circumstances that I haven’t considered? Whatever you’re thinking – I would love your feedback! Help me make this Road Trip Survival Guide the best it can be.

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