Modern vehicles make a lot of demands upon their batteries. We expect our batteries to be reliable, have a large reserve capacity and a long life span, and be maintenance-free. In short, once a battery has been installed, we no longer want to think about it. Here's some tips on how to choose a battery that will serve you well.

For automotive applications, there are basically three types of batteries: conventional, maintenance-free, and recombination.

Conventional Batteries

A 12-volt automotive battery contains six cells. In each cell is a series of alternating positive and negative plates, between which are isolator or separator plates to keep them apart. All the negative plates in the battery are connected, as are all the positive plates. Each plate has a grid construction, and to this grid, the plate's active material - sponge lead - is bonded. The plates in each. cell are covered with a solution of distilled water and sulfuric acid (electrolyte). As the battery discharges (supplies electricity), the acid in the electrolyte reacts with the active material in the battery plates, forming lead sulfate and weakening the electrolyte solution. Conversely, as the battery is charged, the acid is returned to the solution, thereby strengthening it, and the used portion of the lead sulfate is converted back into active material in the plates. During this process, hydrogen and oxygen molecules are off-gassed out of the electrolyte, which is why a conventional battery often needs topping up with distilled water. The charge and discharge cycle also means that some lead sloughs off the plates. Over time, this builds up in the bottom of the case, reducing the overall capacity of the battery fluid. When enough material builds up, the plates will short out, and you're stuck with a dead battery.

Maintenance-Free Batteries

Closed (maintenance-free) batteries are essentially the same as conventional batteries, except that they contain extra electrolytes in the partially sealed case. However, over time, this excess fluid is used up as fluid slowly off-gases hydrogen and oxygen molecules through the vents. Because these batteries cannot usually be topped off, once the plates begin to be exposed, the battery's life span is over. Usually, this takes a long period of time, which is why these batteries often last longer than conventional batteries. However, in situations where frequent, rapid charge/discharge occurs (such as when running a winch or powerful spotlight without running the engine), a maintenance-free battery may not outlast a conventional one.

Another type of maintenance-free battery is the gel-type battery While these batteries cannot leak or spill fluid and can be installed at odd angles, they do have a weakness. Using electrolyte gel necessitates the use of thinner plates so that adequate dispersion of the acid through the active material occurs. Since gel batteries are also sealed, they cannot be topped off and care must be taken when charging so they don't overcharge and gas-off, which will result in excessive sloughing of the plates, premature reduction in electrolytes, and eventual battery failure. This means that during the harsh vibrations associated with trail riding, a marginal gel battery can fail completely as the plates literally fall apart.

Recombination Batteries

The recombination battery is overall the best battery for off-road and heavy-duty use. They're called recombination because they recombine the gas formed during charging, channeling it into the separators so it doesn't vent out of the battery and reclaiming the water to keep electrolyte concentration at optimum. They are completely sealed (except for a reseating pressure-relief vent) and require no topping off of fluids. Recombination batteries can use either liquid or gel-type electrolytes and are different from other batteries because the acid is bound into the separators and pure lead can be used in the plates. Because of the purity of the materials used, there is no sloughing and the plates in these batteries can be very tightly packed. The result is a powerful, compact battery with quicker charging time, lower internal resistance than conventional or maintenance-free batteries, and a longer life span. In fact, for a conventional battery to deliver the same amount of starting power as a recombination battery, it would have to be two or three times larger. Because they contain no liquid as such, recombination batteries can be mounted in any position, will work when the case is damaged, and won't leak in a rollover. In short, for off-road use, they are just about the perfect battery.

How Batteries Are Rated

Battery ratings are a determination of how much power a battery can produce under marginal conditions. There are a number of ways to determine a battery's output, but ratings by ampere hour (Ah), cold-cranking amperes (CCA), and reserve capacity are the most common.

Ampere hours are determined by the SAE 20 test. This test is designed to show the amount of current that can be drawn from a battery for 20 hours without the voltage dropping below 1.75 volts per cell. In real-world terms, this means that a healthy battery should be capable of keeping the parking lights lit for 20 hours. For starting your truck, Ah doesn't mean much. However, for powering accessories without the engine running, this can be an important measurement.

Cold-cranking amperes or CCA is the unit of measurement that generally determines a battery's ability to start your engine. CCA is a measurement of the worst conditions under which a battery can be expected to deliver current, and it tests how much current in amperes a battery can deliver under extreme cold. According to the American SAE standard, CCA is determined by measuring how much current can be delivered in amperes for 30 seconds at -18 degrees C with a final voltage of 7.2 volts per cell or higher.

Reserve capacity is an important measurement for the total capacity of the battery and shows how long a battery can keep the engine running if the alternator/generator fails. Reserve capacity of a battery is measured in minutes at room temperature (approximately 70 degrees F). During this test, 25 amperes is drawn from the battery for as long as the voltage does not drop below 10.5 volts. For off-road use, it's a good idea to make sure any battery you purchase has a reserve capacity of at least 120 minutes.

Reserve capacity is also important for those times when you need to run a radio, spotlight, winch, or other electrical accessory without running the engine.

A Batteries Two Enemies

Although just about all modem batteries are pretty reliable, there are two enemies that can grind even a brand-new battery to a halt - extreme cold and extreme heat. Batteries are at their best with internal temperatures (not ambient) above 50 degrees F and below 105 degrees F. Below and above this range, problems can develop, and a dead, damaged, or . useless battery can be the result.

We've all noticed that under extremely cold conditions (below freezing), the battery will turn over the starter motor slowly, if at all. This is because when the internal temperature of the battery gets below the optimum range, the chemical reaction inside the battery happens more slowly, and for every 10-degree drop below freezing, the time that the chemical reaction takes doubles. Because of this increased resistance, the voltage in the battery drops and cannot turn over the engine.

Heat can also have an adverse effect on your battery's overall health. Battery power is reduced when it's subjected to excessive temperatures, but the problem may not be immediately noticed until the temperature drops. At higher temperatures, the chemical reaction within the battery is more rapid. The battery can produce more energy more quickly. This is good, right? Wrong. The higher rate of energy production results in an increase in off gassing; the water in the battery is vented out as hydrogen and oxygen molecules and the rate of internal corrosion, or sloughing, increases. This can result in a short in one or more cells that is not noticed until cold weather diminishes the overall ability of the battery.

What to Buy

When it comes to batteries for automotive use, there is no such thing as a perfect battery. Any battery can fail if it is neglected, constantly overloaded, or overcharged. The important thing to remember is to get the right battery for your needs, one that is rated for your vehicle and all the accessories you use. Generally, this means a high Ah, high CCA, and high reserve capacity. Also, make sure you buy a quality unit. Don't be fooled by the low price of the budget shops. Batteries sold in the no-name-battery discount stores often are poorly assembled and use inferior materials in the plates and separators. Name-brand batteries, such as AC-Delco, Sears DieHard, Exide, Interstate, Optima, and others, are manufactured to the highest standards, delivering high reliability combined with long life.

For off-road use, however, we feel that the recombination battery is the best overall, since it delivers high output, needs no maintenance, holds up well to the rigors of off-road driving, and has a quick recharge rate, as well as a long life span. It is a particularly useful battery for the off-roader because it has no liquid to leak out and can be mounted in any position (even upside down). Because of this, it won't corrode battery trays or cables and is safe in a collision. You can actually shoot a 45-caliber bullet through the battery casing and it will still crank at full power. Try that with a conventional battery, and you have a leaking mess that will at best produce minimal voltage.

Although recombination batteries are sold under various brand names, Optima's 800U is the original and also the only battery available with both top posts and side terminals, a feature that makes it especially well suited for specialized installations and powering accessories and where there is installation room for only one battery Since we also run a winch and driving lights from the starting battery, it has to be a powerful one. The 800 CCA and 120 minutes of reserve capacity the Optima offers means we can rely on the unit as a power source for lights and winch use when the engine is down, without sacrificing starting ability. Additionally, the side terminals make it easy to power the winch and other accessories directly off the battery without disconnecting the main power cables and disabling the vehicle's computer. This makes for a clean installation without a lot of cable clutter at the main battery posts, which is especially important when there's limited space around the battery top.