Owner`s manual

General Information
TruSine 4.5 kW Inverter Page 26 Owners Manual
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.
6.5 Sizing the Inverter Battery
Sizing a battery system for an inverter application can be a very tedious task if all the different variables, such
as discharge rate, depth of discharge, and operating life time are included in the calculations. To simplify these
calculations and get a reasonably correct battery size, we will assume: 1) A 50% depth of discharge for the
purpose of obtaining a reasonable life time for a reasonable battery system cost, 2) there is no charge current
into the battery system, 3) the batteries are in a fully charged state at the beginning of the discharge cycle, and
4) the DC current draw from the battery does not exceed 1/3 the C rate for any length of time.
Follow the steps listed below to find the AH capacity required for your application.
Step 1: Make a list of each appliance, its power requirement in watts, and the amount of time in hours it will
be operating between charging cycles. Note: If the appliance is rated in amperes (amps) instead of
watts, multiply the amps by the voltage (120 or 240) to get watts.
Step 2: Calculate the watt-hours required for each appliance by multiplying the power requirement by the
operating time of that appliance.
Step 3: Calculate the total watt-hours needed by adding together the watt-hours of each appliance.
Step 4: Find the amp-hours consumed by dividing the total watt-hours found in step 3 by 10 for 12 volt DC
systems or by 20 for 24 volt DC systems.
Step 5: Multiply the amp-hours consumed by 2 (for 50% depth of discharge) to get the battery amp-hour
capacity desired.
Example 1: Follow Steps 1 through 3 (above)
Appliance Power Rating
Operating Time Watt-Hours Consumed
TV, VCR, Stereo 225 watts 2.5 hours 563 watt-hours
Small Refrigerator 300 3.8 1,140
Microwave 800 0.3 240
TOTALS 1,943 watt-hours
Step 4: Amp-hours consumed = 1943 watt-hours ÷ 20 = 97.15 amp-hours for 24 a volt system.
Step 5: The minimum battery size for this application is 2 x 97.15 = 194.3 amp-hours.
6.6 Battery and Charging System Considerations
The Battery and DC Charging System is a very important part of your inverter installation responsible to supply
all of the DC power required by the inverter. The system normally consists of the primary charger (engine
alternator or photovoltaic array), a secondary charger, if used, the battery, and other equipment which may be
used such as battery isolator diodes. The complexity of the system depends on the way the inverter is used.
In some cases, such as utility or service vehicles, the system may be as simple as the engine alternator and
the cranking battery which also powers the inverter. In most cases, additional equipment is needed to provide
additional DC power and/or protection. These systems can be grouped into two categories, the single battery