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Car And Deep Cycle Battery

Frequently Asked Questions

The six major keys to longer battery service life

  • Using the battery manufacturer's recommended temperature compensated charging voltages and procedures
  • Reducing the average Depth-of-Discharge
  • Adding distilled water when required and practicing good preventive maintenance
  • Keeping the batteries cool in hot temperatures
  • Reducing the number of discharge-charge cycles
  • Periodically equalizing wet batteries


Please wear glasses when working with a lead-acid battery in the unlikely event it might explode from the gasses produced during charging. Safety First!

For a starting battery, at the first signs of slow starting, dim headlights at low RPM, ammeter indicating discharge at higher RPM, or if the battery seems to be losing performance, fully recharge the battery, remove the surface charge, and load test it and the charging system. Some auto parts or battery stores will test your battery, charging system or starter for free. Weak or bad batteries can also cause stress or premature failures of charging systems and starters and vice versa. (Please see Section 4.)

Perform regular preventive maintenance on starting and deep cycle batteries, especially during hot weather and before cold weather. Keep the battery top clean, cable mating surfaces, posts and terminals free from corrosion, and routinely tighten cable connections and retention alternator belts. Keep non-sealed wet batteries (with filler caps) filled to the proper level with distilled, deionized or demineralized water, but do not overfill or use tap water. The plates must be covered at all times to prevent internal battery explosions or sulfation. (Please see Section 3.)

In hot climates try and keep batteries as cool as possible. For under the hood, use a non-sealed wet starting battery (with filler caps so you add water) or a sealed spiral wound AGM VRLA battery.

For batteries not in weekly use, people kill more deep cycle and starting batteries with bad charging practices than batteries will die of old age. To prevent permanent sulfation and especially in hot weather, in a well ventilated area, keep the battery continuously connected to a "smart" or float charger matched to the battery type; recharge the battery whenever it drops below 80% State-of-Charge (SoC); or use AGM (Ca/Ca) or Gel Cell (Ca/Ca) VRLA battery. A cheap, unattended, unregulated "trickle" charger can destroy a battery by overcharging it. (Please see Section 9. for more information on charging and chargers.)

When buying a replacement starting battery, buy the heaviest and freshest battery compatible with the vehicle's charging system, with the largest Reserve Capacity (RC) and longest free replacement warranty that will physically fit in your vehicle, and sized with the cranking amp rating for the coldest climate the engine is started in. For deep cycle batteries, buy the freshest and heaviest battery with thickest plates and Amp Hour (AH) capacity that best suits the application, matches the charger, and has the lowest Total Cost of Ownership.

Avoid a deep discharge (below 20% State-of-Charge or 12.0 VDC) of the battery because this could prematurely kill it, due to cell reversal. After deep discharges or jump-starts, fully recharge a starting battery with an external charger, remove the surface charge, and load test the battery and charging system for latent damage. (Please see Section 4.)

Temperature and temperature compensation matter! Heat kills batteries and cold reduces their available capacity.

For longer battery life, do not add battery acid (except to replace electrolyte spills) or additives, keep your battery securely fastened, recharge batteries within 24 hours of each use, use thicker plates, and if recommended by the battery manufacturer, equalize it. Lowering the average Depth-of-Discharge (DoD) percentage will significantly increase the service life of any lead-acid battery. (Please see Section 11. for more information on increasing battery service life.)

For starting and motive deep cycle batteries, match the charging system (or charger's settings) to the battery type, recharge at 77° F (25° C) unless temperature compensated, and insure that the charging system produces enough power to keep the battery fully charged based of your electrical use and driving habits. Use battery charger (or charger settings) sized not to exceed 25% of the total Amp Hour battery capacity and adjusted to the battery manufacturer's recommended charging voltages with good ventilation, especially when recharging wet non-sealed batteries (with filler caps). A better approach is to slowly recharge your starting and deep cycle batteries over eight to ten hours.

For negative grounded systems, always jump start 12-volt batteries POSITIVE (+) terminal to POSITIVE (+) terminal and NEGATIVE (-) terminal to the frame or engine block away from the battery or or use AGM (Ca/Ca) or Gel Cell (Ca/Ca) VRLA batteries to greatly reduce the risk of a battery explosion. (Please see Section 6. for more information on jump starting.)

For deep cycle batteries, try to avoid shallow discharges (less than 10% Depth-of-Discharge) or deep discharges (more than 80% Depth-of-Discharge or less than 12.0 VDC). This could prematurely kill them. Using an adjustable low voltage disconnect set at 80% Depth-of-Discharge (DoD) or approximately 12.0 VDC will increase the batteries' service life and help protect the batteries and valuable electronic and electrical appliances. (Please see Section 11.)

Do NOT use wet lead-acid batteries around salt water. If salt water is mixed with the battery's electrolyte, deadly chlorine gas is produced.Only use sealed AGM (Ca/Ca) or Gel Cell (Ca/Ca) VRLA batteries around salt water.

Remove the surface charge before testing. For non-sealed batteries (with filler caps), use a hydrometer to check Specific Gravity (SG) in each cell because it is more accurate than a DC voltmeter to determine the State-of-Charge (SoC). For sealed batteries, use a accurate (.5% or better) digital DC voltmeter to measure the Open Circuit Voltage (OCV) to determine the SoC. (Please see Section 4. for more information on testing batteries.)

If the temperature is below 0 degrees F (-17.8 degrees C) and you are not using an AC powered engine block and battery warmer or if the vehicle can not be parked in a warmer location, then disconnect the battery, take it indoors, keep it fully charged, and reconnect it just before starting the engine. Alternatively use two 12-volt AGM (Ca/Ca) batteries in parallel and a low viscosity synthetic oil in the engine. Batteries that have less than a 40% State-of-Charge will freeze at 0 degrees F (-17.8 degrees C) and fully discharged batteries will freeze at approximately 20 degrees F (-6.7 degrees C).

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