7
6.0 – SYSTEM DESIGN
The design of a complete EP System is simple. All
that is required is selection of the proper batteries.
Convenient graphs for this are provided.
6.1 – Input Surge Protection
Although the EP has some built in surge protection,
it is often desirable to use an input surge protector
as insurance against unwanted high voltage input
surges. Systems in remote areas are especially
prone to lightning-induced damage.
6.2 – Battery Type Guidelines
The EP is specifically designed for deep cycle lead-
acid batteries. It will work with either Gel or AGM
maintenance-free batteries. It should
NOT
be
used
with wet lead-acid batteries, automotive
batteries, or
nickel-cadmium batteries
.
6.3 – Battery Ventilation / Enclosures
Batteries should never be placed inside a sealed
enclosure or area because they will vent explosive
gases during charging. While the quantities of gas
are generally quite small, a sealed area allows the
concentration of hydrogen to exceed safe levels.
6.4 – Battery Sizing
The EP will work with a wide variety of battery
capacities listed in the table 6.4.1.
Table 6.4.1 – Min / Max Battery Capacities
Parameter
MODEL
EP 12-10
EP 24-5
Min. Bat. Cap.
34 Amp-hours
17 Amp-hours
Max. Bat. Cap.
400 Amp-hours
200 Amp-hours
The correct battery capacity for your system will
depend on two factors: your load; and the length of
time you wish to have back-up power. The larger
the battery, the longer the back-up period or “HOLD-
UP” time will be. The “RECOVERY” time as well as
the system cost increases as well.
Your actual battery capacity should be calculated by
multiplying your
average
load in Amps (A) times the
number of hours (h) of back-up desired, plus a
safety factor of 1.5 (SF). The safety factor is
important as it takes into account a cold battery, or a
battery at the end of its life.
Battery Capacity = A x h x SF
Thus a 1A load with a desired back-up time of 48
hours with a 1.5 safety factor will require a 72Ah
battery. 1A x 48h x 1.5 = 72Ah
When combining batteries in series or parallel, it is
important to know the rules for determining the total
capacity of the battery bank:
1. When combining batteries in parallel, add the
battery’s capacities to arrive at the total.
2. When combining batteries in series, do not
add the capacities. The total capacity equals
the capacity of one battery in the series
string.
Figure 6.4.2 shows an example of some typical
battery banks and their capacities:
100Ah TOTAL
CAPACITY
50Ah TOTAL
CAPACITY
24 VOLT SERIES CONNECTION
12 VOLT PARALLEL CONNECTION
50Ah
50Ah
50Ah
50Ah
Figure 6.4.2 – Battery Banks
