General Information
TruSine 4.5 kW Inverter
Page 25
Owner’s Manual
6.4 Battery Terminology and Ratings
Batteries used for automotive applications generally are lead-acid storage batteries. They can be separated
into two categories according to their use: engine cranking batteries and deep cycle batteries. The engine
cranking battery is specifically designed to supply hundreds of amps for a short period of time to start an
engine. Cranking an engine usually uses a small portion of the battery's total capacity and once the engine is
running, the battery is quickly recharged by the engine's alternator. The deep cycle battery is specifically
designed to deliver current for extended periods of time and can be almost totally discharged before
recharging.
The "deep cycle" lead-acid battery is designed to withstand the deep discharge/recharge cycling that is typical
of most inverter installations. These batteries are available in the "maintenance free" style where the electrolyte
does not need to be checked or replenished and they also are available in the gelled electrolyte style or "Gel
Cells". Deep cycle batteries are generally advertised for use in recreational vehicles or boats and are
sometimes referred to as RV or marine batteries.
Battery Council International (BCI) is a voluntary industry organization which has helped to standardize battery
ratings. Ratings in use at this date are:
CCA (Cold Cranking Amperes): Rating in amps a battery cold soaked at 0°F or –20°F will carry for 30
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
