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Both single-use and rechargeable batteries are essential to your survival during a zombie apocalypse, so scavenge as many as you can during your supply runs. As you’ll see in Chapters 9, 10, and 11 of this book, you can use batteries to power zombie-distracting devices and communications devices. Of course, both types of batteries have different merits. Let’s explore those now so you can decide which deserves a spot in your go bag.

SINGLE-USE BATTERIES

AA batteries have a long shelf life, and to operate many small appliances, it makes sense to scavenge a good supply of these. They also run out of power slowly. For example, if your flashlight begins to dim, you’ll still get a few valuable minutes of light before the battery completely dies. Note that rechargeable AA batteries usually give out much more quickly than single-use batteries—and with less warning.

RECHARGEABLE BATTERIES

Lithium polymer (LiPo) batteries have transformed mobile devices because they’re lightweight and can store a lot of energy. Since a cellphone is so easy to carry around, you might think LiPo batteries are a good rechargeable choice for any portable postapocalyptic device. But be warned: they have a few quirks:

• They are prone to catching fire if overcharged, punctured, or cut.

• They require special charging circuits.

• They don’t work well at extremes of temperature.

In short, for storing energy that you generate, it’s better to use the lead-acid batteries that you find in cars. For a start, there should be a plentiful supply of these. They also have the advantage of working at low temperatures, and they are much more forgiving of overcharging or continuing to be discharged after they are empty than other types of rechargeable batteries. The only real downside to lead-acid batteries is that they are really heavy, so when you need to scavenge car batteries, don’t be tempted to load your pack with much else. Otherwise, you’ll quickly find yourself too overburdened to escape a pursuing zombie.

BATTERY CHARGING

Under normal circumstances, the easiest way to charge a battery is to use an AC-powered battery charger. Since you won’t have access to AC (unless you’ve hit the jackpot and found a working generator), you need to consider ways you can generate electricity to charge batteries.

In the project that follows, you’ll learn how to generate electricity and charge batteries using solar power, in many ways the easiest solution to postapocalyptic power problems. You’ll then discover how a stationary bicycle and a car alternator can be adapted to charge batteries. The principles you learn here also govern using water wheels and wind turbines. In fact, anything that can turn the shaft of a car alternator at a reasonable speed and with reasonable force can be used to generate power. A drive belt is a good way to link whatever is turning to the alternator and provide some gearing so that the alternator moves fast enough.

PROJECT 1: SOLAR RECHARGING

This project will show you how to make a simple setup that charges a 12V car battery using solar power.

SOLAR PANELS

Photovoltaic (PV) solar panels are silent, require minimal maintenance, and will just sit there happily generating electricity. They generate a lot more electricity when the sun is out, but they still make useable amounts of electricity on an overcast day. Obviously, they’re useless at night, which is why you’ll use them to charge batteries, not power a device directly. They also need to be situated with a clear view of the sky and out of zombie climbing height, as an undead entity partially obscuring a solar panel will drastically reduce its efficiency.

You may find solar panels to scavenge on the roofs of houses or even in arrays on the ground. Your electricity needs are likely to be relatively modest, so one or two panels will be plenty. After all, we’re talking about survival here; the hot tub can wait.

As you might expect, the generating capability of solar panels is measured in watts. But make no mistake: a solar panel labeled “100W” may generate just about 100W at noon on a cloudless day on the equator, but most of the time, it will generate a lot less than that.

Solar panels incorporate different types of technology, the most common types being monocrystalline silicon and polycrystalline silicon. The mono panels are more efficient and produce more power per square foot, but the poly panels still make perfectly good electricity. They just need to be a little larger to make as much. It does not matter what type you take; all you really need to be aware of is the number of watts. If you turn the solar panel over, you should find a label that gives you all the key data about the panel.

CHARGE CONTROLLERS

Domestic solar installations don’t charge batteries. Instead, a complex piece of equipment converts the low-voltage DC produced by the solar panels into high-voltage AC. The converted power is first used to meet the demands of the house’s AC wall sockets and lighting. Then anything left over goes into the power company’s AC lines, and the power company pays for the contribution of excess electricity. Well, that’s what happens if you’re reading this before the apocalypse. Otherwise, it’s likely everyone at the power company has become a zombie, and money has become meaningless.

Instead of giving your excess electricity away to a power company that doesn’t care and won’t pay for it, store it in batteries for later use. This project works just like the way you’d manage electricity for a motor home or boat that uses PV cells to charge its batteries when the vehicle is not in use.

Rather than build an electronic circuit to control the charging, it’s much easier and more reliable to use a ready-made charge controller. If you’re buying preapocalypse, then pick one up on eBay, at another online retailer, or at a physical store, like Fry’s. If you’re buying postapocalypse, then they’re available free of charge from physical stores.

WHAT YOU WILL NEED

To make this project, you’ll need the following items.

ITEM

NOTES

SOURCE

Charge controller

7A (or more) 12V

eBay, Fry’s (4980091), abandoned RVs and boats

PV solar panel

20W-100W

eBay, Scavenge

Car battery

12V

Auto parts store, Scavenge

2x heavy-duty alligator clip

7A or more

Auto parts store

Electrical cable

7A

Scavenge

Terminal block

10A

Home Depot, Lowe’s, Menards

Multimeter

Simple multimeter

Auto parts store, eBay, Fry’s

Solar panel specifications have become pretty standardized. Look for a solar panel that generates between 20W and 100W and is labeled as 12V. That means the panel is suitable for charging 12V batteries. Nominally, 12V solar panels will actually produce upwards of 18V.

The power cable needs to be long enough to connect the solar panel to the charge controller. This cable could be an AC outlet extension with the connectors cut off each end. Thin, low-current cable has a higher resistance to the flow of current than higher-current cable, which will waste precious power. For example, a 10A AC outlet extension cable that’s 30 feet (10 m) long will waste about 0.5W of power for a 20W solar panel charging at about 12W. For this reason, use a thick cable and keep its length short if you can.