These readings should be taken by a digital voltmeter prior to charging the battery.  Corresponding hydrometer readings from the 12 volt scale portray the same relative state of charge regardless of battery voltage.

12 volt battery                  6 volt battery        State of Charge

12.66                                 6.33                           100%

12.58                                 6.29                             90%

12.51                                 6.25                             80%

12.45                                 6.22                             73%

12.43                                 6.19                             70%

12.35                                 6.17                             60%

12.28                                 6.14                             50%

12.19                                 6.09                             40%

12.12                                 6.06                             30%

12.04                                 6.02                              20%

11.97                                 5.98                              10%

11.81                                 5.91                               -0-

Cold Cranking Amps is the most common rating for relative battery performance. Conceived as a quick reference many years ago, the rule of thumb was one CCA per cubic inch of engine displacement.  That was before the advent of usage metric engine displacement, and the addition of much more electronic load in today’s vehicles.  Now the best way to determine the correct CCA rating is to check the original equipment battery rating, and select a battery that meets or exceeds that rating.

Can I get too much CCA?

The American way is to be exceptional, and many people approach battery ratings the same way.  With batteries, we have seen rating creep the last few years, partly due to competition among manufacturers and partly due to progress in the type materials used internally in batteries.  In the southern half of the U.S., under hood heat takes a heavy toll on batteries above 700 CCA.  Unless the manufacturer recommends a higher number, we discourage the temptation to go higher than that.  More cranking power requires more plates in the battery, thus reducing the available space for electrolyte.  “Acid starvation”, which dramatically reduces battery life, can occur in extremely high rating batteries.  Many newer vehicles have moved the battery away from the engine compartment, so the heat issue has been alleviated, somewhat.  For vehicles that operate in northern climates, heat is less of a factor.  

What is the difference in the CCA and CA rating?

CCA is the number of amperes a new battery can deliver at 0 degrees for 30 seconds while maintaining a minimum of 1.2 volts per cell. (7.2 volts for a 12 volt battery)  CA(Cranking amps) is the same measure taken at 32 degrees.

What does the RC rating on my battery mean?

Reserve Capacity refers to the number of minutes a new fully charged battery can deliver 25 amps of discharge.   The RC rating was utilized for several years to estimate the length of time a battery could power lights, wipers and heater in the event of charging system failure.  Now vehicles may draw significantly more than 25 amps to run these critical systems.  RC ratings are also the standard comparison for deep cycle and motive power equipment applications.

Water or electrolyte(acid) to top off a battery?

Unless the battery has been spilled, clear odorless water, such as distilled should be used.  Avoid any water that has a high mineral content, especially iron.  If the battery is discharged, fill only to the top of the plates or separators, then re-charge and top off to the bottom of the vent filler neck.  Adding electrolyte risks creating an imbalance of the specific gravity, and will most likely shorten life.  As with any service work around batteries, take safety precautions and wear protective eyewear.

What is the difference between Gel and AGM batteries?

“Gel” is a generic term frequently used to describe Sealed Valve Regulated batteries.  But, it also refers to a particular type of SVR battery that has silica added to the electrolyte to create a gel solution that is immobile when it is added to the battery during the manufacturing process.  Gel batteries are particularly shock resistant and spill proof, and are best utilized in a controlled environment and charging regime.

AGM(Absorbed Glass Mat) batteries have a unique separator between the plates that absorb the electrolyte, holding it in suspension against the plate surface.  Because there is lower resistance between the plates than a gel battery, this type battery is frequently used in starting applications, and for a dual purpose battery application.  Some manufacturers utilize a spiral plate cell when assembling an AGM battery, but we believe a standard flat plate design is more efficient.  Many automotive manufacturers apparently agree, as this type AGM battery is becoming more common as OEM equipment.  We have many sizes available for automotive and equipment replacement with AGM chemistry.

Sealed Valve Regulated refers to controlled venting of both of these type batteries to prevent moisture loss, but still allow for safe release of accumulated gas in the event of high overcharge.

 After the unusually hot summer of 2011, battery failures will show sooner rather than later when cold snaps occur this year.  Batteries can recover fairly quickly from a cold spell, but prolonged ambient temperatures above 90 degrees are brutal to a lead acid battery’s internal chemistry.

A quick way to determine if you will need to replace your vehicle battery this year is to check its age.  Most battery manufacturers use a letter/numeral date dot that combines the month of delivery(A=January through M=December) with the last number of the year.  So, B-7 equals February of 2007.  A five year old battery is well past the mean service life of 43 months in the southern half of the U.S.

Another indication of a weak battery is a straining sound from the starter motor while turning the key to start the engine.  If a starter is not getting full voltage-typically 9.6 volts under load-it will not turn as fast as normal, and the resulting strain sound indicates the battery is most likely weak.  Prolonged low voltage will cause damage to the starter, maybe even requiring replacement.  That is much more expensive and time consuming than simply replacing the battery.

So, check the age of your battery, and listen closely when you  turn the key. The time to change your battery is when you have time to spare.

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