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CCA and RC must be displayed on the battery:

  • Cold-cranking AMPs (CCA). The CCA number is displayed on the battery (see label below). The higher the CCA number, the better suited the battery is for cold-weather starts.
  • Reserve Capacity (RC). The RC number is also displayed on the battery (see label below). The higher the RC number, the greater the reserve your battery has in the event of an equipment failure -- such as an alternator that has quit working or a broken fan-belt.
    My car battery is rated at 800 CCA, 1,000 Charging Amps and 105 RC.
Batteries are also listed by Battery Counsel International (BCI) size (group) codes. See Size codes in the products page.
Common sizes are Group 65 (most Ford corp.), 34/78 (large Chrysler, Jeep Wrangler) and 75 (midsized Chrysler) 35 (other Japanese) and 24 (Acura CL, TL, Honda Accord)

For excessive vibration applications, in off-road operation, or extreme conditions, it is best to use a spiral wound AGM (Absorbed Glass Mat) VRLA (Valve Regulated Lead-Acid) car or deep cycle battery because there is no shedding of active plate material since the plates are immobilized.
Examples are Johnson Controls' Optima, Exide's Select Orbital or Maxxima, or EnerSys' Cyclon.
See Darden's FAQs

Before discharge the sulfuric acid releases its first protron.
H2SO4  →  H+ + HSO4

Discharge reaction: s - Solid, aq - liquid
At "+" plate (cathode):
PbO2 +3H ++HSO4+2e  →  PbSO4 +2H2O 
(s) (aq) (aq)  dis (s)  
At "-" plate (anode):
Pb+HSO4 → PbSO4 +H ++2e 
(s) (aq)dis(s) (aq)
If we combine the two half-cell reactions together, we get the full-cell discharge rection.
Pb+PbO2 +2H2SO4  → 2PbSO4 +2H2O  
(s) (s) (aq)disch(s)

There is an electric field in the electrolyte that causes negative ions (in this case bisulfate) to drift toward the "-" plate. The reaction produces a negative ion (hydroxyl) which drifts away under the influence of the aforementioned field. See: Lead-Acid Battery Half-Cell Reactions

* Flooded/Wet cell batteries
* Sealed Lead Acid (SLA) or Valve Regulated Lead Acid batteries (VRLA):
    - AGM: Absorbed Glass Mat batteries
    - Gel cell batteries
    - Carbon Foam Lead Acid batteries
See Lead Acid Battery Types in home and garden for more

There are several risks with flooded/wet lead-acid batteries.

  • Sulfuric acid is extremely corrosive to metals and can cause acid burns.
  • Excessive charging voltages will generate oxygen and hydrogen gas by electrolysis of water, forming an explosive mix.
  • As the battery discharges and the concentration of sulfuric acid decreases, the electrolyte is more likely to freeze in cold weather.


  • Absorbed Glass Mat (AGM) - A type of Sealed Lead-Acid (SLA) battery with the electrolyte in in an absorptive glass mat sandwiched between the plates.
  • Ah - Ampere Hour - Battery Capacity in amps x hours before it needs to be recharged.
  • BCI - Battery Counsel International
  • Cold Cranking Amps (CCA) represent the current a starting battery provides continuously for 30 seconds at 0 degs. F before voltage is drops to 1.7 volts per cell at which point it is fully discharged.
  • Deep cycle or Deep discharge batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates. The major difference between a true deep cycle battery and others is that the plates are SOLID Lead plates - not sponge. This gives less surface area, thus less "instant" power like starting batteries need.

    Amp-hour ratings of deep cycle batteries are based upon a discharge rate at 1/20 capacity, expressed as C over 20". A marine battery rated 200ah at C20, when discharged continuously at 10 amps, at 80° F., sustains the load for 20 hrs.
    Most smaller deep cycle batteries (including AGM) use Lead-Calcium plates for increased life.
    Deep Cycle in Products

  • Depth of discharge (DoD) is percentage of capacity available during a charge-discharge cycle.
  • Gel Cell - A type of Sealed Lead-Acid (SLA) battery with a gelled electrolyte. They are "valve regulated", which means that a tiny valve keeps a slight positive pressure. Portable Jump Start batteries are typically gel cells.
  • Marine batteries are usually actually a "hybrid", and fall between the starting and deep-cycle batteries. In the hybrid, the plates may be composed of Lead sponge, but it is coarser and heavier than that used in starting batteries. "Hybrid" types should not be discharged more than 50%.
  • Marine Cranking Amps (MCA), are measured at 32 degs. F.
  • Reserve capacity (RC) is the time a starting battery can sustain a 25 amp load before cell voltage drops to 1.7Vpc (V per cell) (=10.2V for battery).
    Ah = (RC / 2) +15.5
    My car battery is rated at 800 CCA, 1,000 Charging Amps and 105 RC.
  • Reticulated vitreous carbon (RVC) - Used in Carbon foam plate batteries.
  • S.A.E. - Society of Automotive Engineers
  • SOC - State-of-charge
  • SOH - State-of-health - SOH can be expressed from 0% to 100%, based on the real-time Ah capacity of the battery measured against the minimum requirements for the application at 25 C.
  • Starting Batteries (sometimes called SLI, for starting, lighting, ignition) batteries are commonly used to start and run engines. Engine starters need a very large starting current for a very short time. Starting batteries have a large number of thin plates for maximum surface area.
  • V.P.C. - Volts per Cell
  • Valve Regulated Lead Acid batteries (VRLA):

Jump Starting
Jump Start Batteries
Battery charging
Battery Ratings in Products
Batteries in Home & Garden
Deep Cycle Battery FAQ
Battery Cable size
Battery Guide at DiffLock 4x4
Replacing a Car Battery at DIY network.
Battery Frequently Asked Questions (FAQ's) and other information

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last updated 14 May 2007