Owner`s manual
General Information
ITC-Series
Inverter Page 26 7/18/03
seconds and maintain a minimum terminal voltage of 7.2.
MCA (Marine Cranking Amperes): Rating in amps a battery cold soaked at 30°F will carry for 30 seconds
and maintain a minimum terminal voltage of 7.2.
RC (Reserve Capacity): Rating in minutes a battery will carry a 25-amp load at 80°F and maintain a
minimum terminal voltage of 10.5.
AH (Amp Hour): At the “20 Hour Rate”, also called the C Rate, a battery having a 100 AH rating must carry
a 5 amp load for 20 hours (100AH ÷ 20 hours = 5 amps) and maintain a terminal voltage of 10.5 at
80°F. (Two 100AH 12volt batteries connected in series provides 100AH at 24 volts. Two 100 AH 12volt
batteries connected in parallel provides 200 AH at 12 volts.).
CCA and MCA are used for sizing an engine cranking battery and have no bearing on a battery's cycling ability.
RC is a rating given to cranking batteries to provide an idea of how long a vehicle could be driven if the vehicle
charging system were to fail.
The most important and probably least understood battery capacity rating is the ampere-hour. One simple
reason the AH rating is misunderstood is that a battery rated at 100 AH cannot always deliver 100 AH. The
underlying reason is the efficiency with which the battery converts its chemical energy into electric energy. The
AH capacity of a battery is affected in the following ways:
Discharge rate: A battery becomes less efficient as the discharge current increases. For example, a typical 100
AH battery is specified to be able to deliver 5 amps for a period of 20 hours. If the discharge current were
increased to 25 amps, the capacity will be reduced to approximately 75 AH (25 amps x 3 hours = 75 AH).
Operating temperature: A battery becomes less efficient at lower temperatures. Most battery manufacturers
specify the battery AH capacity at 80° F. At a temperature of 32° F, the same battery will have only about 65% of
its rated capacity even though it may be fully charged. At a temperature of 0° F, a battery's capacity will be
reduced to about 40% of its rated capacity.
Battery age: As a battery is used, the active material on the battery plates will gradually deteriorate and become
useless. As the battery gets older, there will be less and less useful material left on the plates and the operating
time will become noticeably shorter. A battery will age faster (loose active material from its plates faster) if it is
deeply discharged regularly, if it is left in a discharged state for extended periods of time, or if it is repeatedly
overcharged.
Series and/or Parallel Connected Batteries: Up to this point we have spoken of the battery as if it were a single
battery. In some cases this may be true, but in general, the battery may be made up of several individual
batteries electrically connected together to form a "Bank" of batteries. Batteries can be connected in series,
parallel, or a combination of series and parallel as long as all of the batteries in the bank are of equal ratings, are
from the same manufacturer, and are the same age. Old and new batteries should never be mixed in the same
battery bank. Mixed batteries will result in accelerated battery failure due to the unequal discharge and recharge
rates.
A series connection is where two or more batteries are connected positive (+) to negative (-). The total voltage of
the battery bank is the sum of the voltage of each battery in the bank. For example, most large custom coaches
require a 24-volt battery to crank the large diesel engine. The 24 volts is usually provided by connecting two 12
volt batteries in series, and sometimes by connecting four 6 volt batteries in series. The ratings of the series
connected battery bank remain the same as the individual battery's rating. If the battery bank is made up of two
8D size batteries in series, each with a CCA of 1050 amps, 425 minutes RC, and amp-hour capacity of 200 AH,
then these individual battery ratings are also the ratings of the entire 24 volt battery bank.
Parallel connected batteries are batteries which are connected positive to positive and negative to negative. They
form a battery bank that has the same voltage as each individual battery. The ratings of a parallel connected
battery bank, in general, are the sum of the individual batteries. For instance, if two 8D batteries are connected in
parallel, and each battery has the ratings given in the paragraph above, then the ratings for the battery bank
become 2100 CCA, 900 minutes RC, and approximately 400 amp-hours. Parallel connected batteries should be
of the same voltage and rating to achieve optimum battery life and performance.