largely unchanged since its invention back in 1860 by Raymond Gaston Planté.
Plantés battery consisted of a series of cells made of two lead plates separated
by a rubber sheet, and the resulting "dinner roll" was then immersed into a
dilute solution of sulfuric acid. While we won dive off the deep end into the
inner workings of battery chemistry, suffice it to say that the modern
automotive battery still realizes its roots with Planté and not much has changed
in the past 140 years - lead grids are still used and submerged in an acidic
electrolyte to form a reduction-oxidation ("redox") chemical reaction with large
amounts of electrical energy as a by-product.
Decoding A Battery
Battery labels will carry notations such as cold cranking amps,
group size, and reserve capacity. These are standards set forth by the Society
of Automotive Engineers (SAE) to make battery selection easier for both the
manufacturer and the consumer, and each one has significant meaning to us
motorists. Since Billy Bob at your local parts store may not know the meaning
either, lets equip ourselves with the knowledge necessary for proper electrical
system maintenance.
Group Size
This is a simple, two-digit number that indicates the size and shape of
the battery according to the vehicles weight and load carrying capacity. This
particular battery is a "Group 51" which is what late model Honda Civics use.
Other cars, such as the Toyota Supra, use a larger battery such as a "Group 24F"
so you can see that larger Group numbers don necessarily mean larger batteries.
Cold Cranking Amps
This number tells us how many amps of electrical power the
battery can provide for 30 seconds - at zero degrees Fahrenheit - while
maintaining a voltage of over 7.2 volts. Our sample Honda battery lists a CCA
rating of 435 amps, or a minimum of 3,132 watts. You can also see that our
sample battery lists a "CA" (Cranking Amp) value of 530 amps. Cranking amps is a
non-standard value that some battery manufacturers are supplying on their
batteries so that the consumer is exposed to an inflated performance claim.
Since lead-acid batteries are based on an electrolyte that is dissolved in
water, lower temperatures will reduce battery performance as the electrolyte
goes toward freezing. So when purchasing a new battery, be sure the salesperson
tells you the cold cranking amp value of the battery and not the cranking amp
value.
Reserve Capacity
While the CCA value is used mainly to judge a batterys peak output
and ability to start your engine on a cold winter day, reserve capacity tells us
how long you can expect a battery to run your headlights and radio while the
engine is off. Larger reserve capacities will also run your engine longer if the
alternator dies. Just as the cold cranking amp value is given in a worst-case
scenario of extreme cold, reserve capacity is a time in minutes that a battery
can sustain a constant 25-amp draw until the voltage drops to 10.5 volts at 80
degrees Fahrenheit. The SAE gives us an example of driving at night (headlights
on) with the defroster and windshield wipers turned on. Our battery lists a
reserve capacity of 70 minutes, giving us approximately one hour of severe road
driving conditions.
Battery Maintenance
You've probably noticed the crusty white buildup on the posts of
your daily driver. This is a fairly normal condition thats caused by small
amounts of battery acid seeping through the seal between the battery post and
the plastic case. The acid splashes up onto the battery post, slightly corroding
it and leaving behind lead oxides - the white crust. Since this crust is not
electrically conductive, its a good idea to clean it off if you should notice
any. This is accomplished by disconnecting the negative battery cable (so you
don get shocked) and brushing with a solution of water and baking soda. The
baking soda neutralizes the stray acids so you don have to re-perform this
procedure in the future. Auto parts stores sell washers made of felt that go on
the battery terminals and their job is to absorb any stray acids before they can
corrode your battery terminals. Auto parts stores will also carry special
greases and coatings, which are intended to keep the terminals corrosion-free,
but we find that they interfere with the electrical connection more than they
help.
Testing
One conventional way to check the condition of a battery is to use a hygrometer.
These are inexpensive and available at any auto parts store. They consist of a
float inside a chamber with a bulb on it. The bulb is squeezed, and then
released to draw electrolyte into the chamber. Then you look at the float and
see how it corresponds to the battery condition chart within the tester. We
experimented with ours to see if storing a battery on a cold concrete floor
reduces its charge and found that this is true. (Apparently, the temperature
differential of ambient air and cold concrete causes a battery to lose its
charge in several weeks.) When using this type of tester, be sure to wear gloves
and goggles because you will spill a little electrolyte (acid), and possibly
fling some. We did just that when removing the flexible rubber nozzle from the
battery.
Performance Electrical Systems
Heavier electrical system loads place more demand on the
alternator, and many people do not realize that heaver alternator loads will
cause the alternator to use more horsepower because the alternator will put more
turning resistance on its drive belt. Enthusiasts will likely want to free up as
much power as possible to turn the drive wheels instead of the alternator, and
this can be helped along by minimizing electrical losses in your vehicle. Since
recharging the battery is potentially the largest load on the alternator, good
battery maintenance is key. Steps to fight corrosion and promote electrical
conductivity of the battery terminals will improve horsepower and fuel economy.
Granted, these gains probably won be noticed by the "butt dyno", but small gains
like these can add up over a 15,000-km annual driving period! (A single dirty
battery terminal can cost at least a tank of fuel or more due to increased
alternator loads on an average car in the United States over a one-year period.)
Keeping the exterior of your battery free of dirt and grease also allows it to
cool better, making it easier to recharge and increasing reliability.