How To: Maintain batteries

Despite improvements in manufacturing and materials, it’s important to stay on top of your batteries’ condition to prevent premature failure.

Thanks to improvements in manufacturing and materials, the number of threats to battery longevity has been reduced from three to one. Unfortunately, the remaining problem isn’t going away anytime soon.

battery longevity has been reduced from three to one. Unfortunately, the remaining problem isn’t going away anytime soon.

Not long ago, the life of many truck batteries was cut short by vibration, overheating or deep discharging, a.k.a. deep cycling. Only the last causes much trouble nowadays, but that’s little comfort to truckers who accidentally have left on-board appliances running while their trucks are shut down for a few days, prompting an unscheduled trip to a battery dealer.

Even when current drain is stopped before replacements are needed, deep cycling can cause permanent damage, says Gale Kimbrough, technical services manager for Interstate Batteries in Dallas.

“Every time you take a starting battery below 50 percent depth of discharge, you’ve eliminated hundreds of normal starting cycles,” Kimbrough says. “Deep cycling deteriorates the batteries’ paste material, which is the chemical substance that actually creates electricity.”

Kimbrough advocates low-voltage-disconnect devices to prevent such problems. These cut the power supply to cab fixtures and outlets when battery voltage falls below a set limit, usually 12.2 to 12.3 volts. A lot of company trucks are fitted with LVDs, much to the disappointment of drivers whose electrical creature comforts occasionally are shut off. Normal current is restored as soon as an afflicted truck’s engine is started.

Battery failures seem to occur most frequently in winter, when starting-power demands increase and battery-power output decreases, the result of slower chemical reactions. Oddly, though, low temperature usually does not harm batteries. It just makes their job more difficult. High temperature is the real killer, says John Miller, senior director of product engineering for Exide Technologies in Alpharetta, Ga.

“I’d bet that most of the batteries dying in winter were severely wounded during the previous summer,” he says. “Heat is really tough on battery components.”

Manufacturers have been able to reduce this problem by using different chemistry. “Within the past five or so years, most heavy-duty battery makers moved to calcium-based or calcium-tin-based alloys,” Miller says. “That’s offered extra protection against overcharging, heat and gassing, which leads to electrolyte loss.”

Buyers can further avoid heat-related trouble by selecting the correct batteries for their operating environment. Doug Merrill, product specialist for ACDelco in Grand Blanc, Mich., warns against buying batteries with excessive cold-cranking amps. “High CCA capacity is important to truckers in extremely cold climates, but it can be detrimental for others,” he says. “Cold cranking output is achieved with additional internal plates. But more plates means more heat.” Ask a reputable dealer for advice on battery selection, Merrill suggests.

The number of batteries on a truck is an equally important consideration, says Interstate’s Kimbrough. “With the types of accessory loads trucks carry today, four-battery sets are better than those with three,” he says. “For example, three 950-CCA batteries will deliver 2,850 cold cranking amps and have about nine hours of reserve capacity [at 3 hours each]. However, four 700-CCA batteries will offer 2,800 cold cranking amps, plus three extra hours of reserve capacity.”

Most automotive batteries today are advertised as maintenance-free. Of course, this doesn’t mean they need no attention throughout their useful life. Regular inspection and testing are necessary for maximum longevity, but experts differ on how often “regular” is. Some truckers make it part of their normal PM schedules, but manufacturers say twice-a-year visits to the battery box are sufficient. Whatever the case, the effort will pay off in lower replacement costs and less downtime.

Positively factual
Here are a few facts to clear up myths and to highlight some interesting properties of batteries.

  • A concrete floor will not cause a battery to discharge faster than any other type of surface.
  • A fully charged battery freezes at minus 85 degrees F, but a battery with 25 percent of charge freezes at 5 degrees F.
  • A hot battery charges (and overcharges) faster than a cold one.
  • All batteries have normal discharge rates that increase with temperature.
  • The faster a battery is discharged, the less total energy it will deliver. This is known as Peukert’s Law.

The steps below apply to batteries featuring removable inspection caps. Please note: Most automotive batteries are filled with sulfuric acid and release hydrogen vapor. The first is highly corrosive, the second highly explosive. Safety precautions are essential. Never go near a battery with an open flame or lit tobacco. Always protect your eyes with goggles or safety glasses.

  1. INSPECT BATTERIES, CABLES AND CABLE ENDS. Remove the battery box cover and look for obvious signs of trouble: cracked or bloated batteries, large patches of sulfation (the greenish-white or bluish crusts that grow on cable ends), cracked or disfigured clamps, chafed or missing cable insulation, excessive dirt and grease. Using a power washer or a blend of water and baking soda, thoroughly clean the tops of the batteries to make inspection easier and avoid contaminating electrolyte later, when the battery caps are removed.
  2. DISCONNECT AND INSPECT CABLES. If you’re unfamiliar with the cabling, draw a diagram of the cables before disconnecting them from the batteries. Always remove the main ground cable first; otherwise, electrical shocks and sparks will occur if your wrench accidentally touches metal while you’re loosening a positive cable end. Examine all cables for damage and loose ends. If replacements are necessary, use only multi-strand products of pure copper to get the most flexibility and current-carrying capacity.
  3. CLEAN POSTS AND CABLE ENDS. Attach a rotary battery-post cleaning brush to an electric drill and scour the mating surfaces of posts and cable ends. In tight spaces, you may need to remove the batteries from the truck first. Use a high-pressure air hose or hand broom to clear loose debris from the tops of the batteries.
  4. TEST WITH HYDROMETER. With batteries fully charged, remove the vent caps from one and suction enough electrolyte to float the hydrometer’s measuring device. Do not remove the pickup tube from the cell. Note the reading, discharge the sample and repeat on the remaining cells and batteries. The specific gravity (density) readings should be within 50 points on a hydrometer’s scale. Significant differences indicate a weak cell; identically low readings indicate a discharged battery. Consult the manufacturer’s guidelines to determine variances for testing in hot or cold weather.
  5. CHECK ELECTROLYTE LEVEL. Before replacing the vent caps, check the amount of electrolyte in each cell. It should be touching, or near, the bottom of the filler tubes. If it’s low, add only distilled water. Never overfill the cells, because any excess liquid will be purged when the batteries heat up during operation, and that will dilute the electrolyte’s strength.
  6. DETERMINE TEST READINESS. Twelve-volt batteries must register at least 12.6 volts across the terminals to be properly load-tested. Use either a digital voltmeter or your load tester’s internal voltmeter (if it has one) to determine test readiness. If the voltage is sufficiently strong, attach the load tester’s clamps to the battery terminals.
  7. LOAD-TEST BATTERIES. Ratchet up the load to half the battery’s CCA rating, maintain for 15 seconds, then recheck the terminal voltage. The minimum should range from 9.1 volts at 30 degrees to 9.6 volts at 70 degrees. Anything lower would indicate a failing battery. The output of all batteries should not vary more than 2/10 of a volt. Otherwise the extra power of the stronger will be wasted trying to compensate for the weaker. Should a battery fail the test, replace it. If all the batteries in a failed battery’s group are more than a year old, replace them all.
  8. REATTACH CABLES. If the batteries were removed from the truck, place them in the tray and assemble the hold-down hardware. Connect all cables except the main ground, referring to your diagram if necessary. Only after all those clamps are tightened should you attach the final ground. Apply sealant to all the cable ends.


  • Combination wrenches
  • Half-inch socket set
  • Assorted screwdrivers
  • Digital voltmeter
  • Load tester
  • Hydrometer
  • Electric drill
  • Battery post cleaner
  • Battery post sealer
  • Battery charger
  • Putty knife
  • Wire brush
  • Eye protection
  • Distilled water
  • Shop towels

ACDelco:, (800) 223-3526
Exide Technologies:, (800) 782-7848
Interstate Batteries:, (888) 772-3600
Optima Batteries:, (888) 867-8462
East Penn Manufacturing:, (610) 682-4231