Car and Deep Cycle Battery Frequently Asked Questions (FAQ) Section 11

The typical overall life of a good quality, well maintained and properly charged battery is:

Pasted Plate Car (used as a Deep Cycle)	0 to 12 months
Pasted Plate Car	4 to 5 years
Pasted Plate Marine/RV	to 4 years
Solid Plate Golf Cart	to 6 years
Gel Cell VRLA	to 8 years
AGM VRLA	to 8 years
Ni-Cad	to 10 years
Calcium Telecommunications (Stationary)	to 10 years
Fork Lift (Motive)	to 10 years
Manchex Industrial (Motive)	to 15 years
Wet Standard (Sb/Sb) Industrial (Stationary)	to 20 years
Ni-Fe	to 20 years

11.1. Protect your car battery from high under hood temperatures with a heat shield or case, keeping it full charged at all times, and well maintained are the easiest ways to extend it's life. In hot climates and during the summer, the electrolyte levels need to be checked more frequently. In a study conducted by the Society of Automotive Engineers (SAE), the under hood temperature has increased more than 30% since 1985.

Chrysler studies have shown that relocating the battery outside the engine compartment has increased the average OEM battery life by eight months. Relocating the starting battery to the trunk or passenger compartment, as Mazda did in their Miata a number of years ago, is becoming more popular by the car manufacturers to protect the starting battery from the high under hood temperatures. However, use sealed VRLA AGM or Gel Cell type batteries because they normally do not produce gas when recharged or wet batteries vented to the outside. If you use a gel cell as a starting battery, you might have to lower the charging system voltages because they are very critical and to keep from overcharging the battery.

For motive and stationary deep cycle batteries, temperature is equally as important for extending the service life of the battery or battery bank. Common sense and chemical intuition suggest that the higher the temperature, the faster a given chemical reaction will proceed. Quantitatively this relationship between the rate a chemical reaction proceeds and its temperature is determined by the Arrhenius equation. Battery life, due to positive grid corrosion, is reduced by 50% for every 18° F (10° C)rise in ambient temperature over 70° F (21.1° C).

11.2. Periodically check the State-of-Charge of car batteries. Based on your driving habits, some vehicle charging systems undercharge the battery causing an accumulation of Lead sulfate known as sulfation. This sulfation reduces the capacity of the battery. If the battery is not fully charged, recharge it periodically with an external battery charges matched to the battery type. Please see Section 9 for more information on charging and chargers and Section 16 for more information on sulfation.

In addition to temperature, car battery life and the number of charge and discharge cycles is dramatically influenced by the average State-of-Charge (SoC) as reflected in the following graph:

If possible in a well ventilated area, recharge a deep cycle battery each day it is used and as soon as possible after each use. The best way to prevent permanent lead sulfation when a starting or deep cycle battery (or battery bank) is not in use, is to maintain it's State-of-Charge at 100% by continuous float charging. If continuous float charging is not possible, recharge before the State-of-Charge drops below 80%. Permanent sulfation kills approximately 85% of all deep cycle and starting lead-acid batteries not in weekly service. Please see Section 16. for more information on sulfation.

11.3. Reducing the average DoD (Depth-of-Discharge), the inverse of SoC, by proper deep cycle battery sizing will significantly increase a deep cycle battery life. For example, a pasted plate battery with an average of 50% DoD will last twice as long or more as if it is has an 80% average DoD. A 20% DoD average battery can last up to five times longer than one with a 50% DoD average. Golf cart batteries will typically have an average 225 cycles at 80% DoD and 750 cycles at 50% DoD. Always avoid DoDs that are greater than 80%. The "sweet spot" (optimum DoD for the greatest amount of power produced over the service life) is generally somewhere between 20% DoD and 60% DoD average. For the AGM battery example below the "sweet spot" is approximately 22.5% DoD based on the greatest amount of power produced.

11.4. Never discharge any 12-volt lead acid battery below 10.5 volts because it can damage the battery. An adjustable low voltage disconnect set for an 80% Depth-of-Discharge (DoD) or less can limit the maximum DoD and protect the batteries and electrical appliances. Leaving your lights or other accessories on and fully discharging a car battery can ruin it due to "cell reversal", especially if it is a sealed, wet Maintenance Free (Ca/Ca) type. Deep discharges in freezing weather will cause the battery to freeze and the expansion of the electrolyte can damage the plates, separators or even crack the battery case. If freezing should occur, you should let your battery thaw, physically inspect case for leakage, fully recharge it with an external charger in a well ventilated area, remove the surface charge, and test the battery and charging system to determine if there is any latent or permanent damage to the plates, separators or case.

11.5. In extremely cold climates, keep the car battery continuously fully charged when not in use, the engine and battery warm, and use low viscosity synthetic engine oil. AGM or Ni-Cad batteries work better in sub-zero temperatures than wet lead-acid batteries.

11.6. In hot climates use the "hot climate or "South" versions of car batteries. They have special plate and connecting strap formulations, lower Specific Gravity levels or increased the amounts of electrolyte to provide more "cooling" for longer service life. Using non-sealed Low Maintenance (Sb/Ca) car batteries is encouraged because you can add water. "Watering" is required more often in hot climates and add only distilled, demineralized or deionized water or, in a emergency, rain water. The plates must be covered at all times to prevent an internal battery explosion or sulfation. Do not overfill, and keep the top of the battery clean. Do NOT add electrolyte (battery acid) to a battery unless some electrolyte has spilled. If the Specific Gravity levels are increased beyond the battery manufacturer's recommended limit, there will be a higher capacity level, but more maintenance and a shorter service life. Please see Section 9.14 for more information on adjusting Specific Gravities.

11.7. Turning off all unnecessary accessories, rear window heater, climate control, and lights before starting your car will significantly decrease the load on the battery while cranking, especially when it is extremely cold.

11.9. In cold climates, increasing the diameter of the battery cables will reduce the voltage loss.

11.10. If required, equalize wet (flooded) and some AGM batteries. Please see Section 9. for more information on equalizing batteries.

11.11. For vehicles not used weekly or driving habits that cause undercharged batteries, continuously float charge the car battery or fully recharge it periodically to remove the accumulated lead sulfate. Please see Section 13 for more information on storing batteries and Section 16 for more information on sulfation.

11.12. Provide adequate ventilation. High ambient temperatures above 80° F (or 26.7° C) will shorten battery life because it increases positive grid corrosion, growth and VRLA "thermal runaway".

11.13. Recharging slowly using the manufacturer's recommended temperature compensated voltages and current.

11.14. Avoid shallow (below 10%) discharges of deep cycle batteries because lead dioxide builds up on the positive plates. In other words, you should discharge a deep cycle battery between 10% and 80% Depth-of-Discharge.

11.15. Use batteries with thicker pasted or solid plates and reduce the number of discharge-charge cycles.

11.16. Apply the correct battery type for the application, that is, starting for starting applications and deep cycle for motive and stationary deep cycle applications.

11. CAN I INCREASE THE LIFE OF MY BATTERY?