28 | SAMLEX AMERICA INC.
SAMLEX AMERICA INC. | 29
It is seen that at DC input voltage of 10V/ 20V, the battery is completely discharged for
C-rate discharge current of C/5 and lower.
In view of the above, it may be seen that a fixed Low DC Input Voltage Shutdown is not
useful. Temperature of the battery further complicates the situation. All the above analysis is
based on battery electrolyte temperature of 80°F. The battery capacity varies with tem-
perature. Battery capacity is also a function of age and charging history. Older batteries
have lower capacity because of shedding of active materials, sulfation, corrosion, increasing
number of charge / discharge cycles etc. Hence, the State of Discharge of a battery under
load cannot be estimated accurately. However, the low DC input voltage alarm and shut-
down function is designed to protect the inverter from excessive current drawn at the lower
voltage.
7.13 USE OF EXTERNAL PROGRAMMABLE LOW VOLTAGE DISCONNECTS
The above ambiguity can be removed by using an external, programmable Low Voltage
Disconnect where more exact voltage threshold can be set to disconnect the battery
based on the actual application requirements. Please consider using the following
Programmable Low Battery Cut-off / “Battery Guard” Models manufactured by Samlex
America, Inc., www.samlexamerica.com
- BG-40 (40A) – For up to 400W, 12V inverter or 800W, 24V Inverter
- BG-60 (60A) - For up to 600W, 12V inverter or 1200W, 24V Inverter
- BG-200 (200A) - For up to 2000W, 12V inverter or 4000W, 24V Inverter
7.14 DEPTH OF DISCHARGE OF BATTERY AND BATTERY LIFE
The more deeply a battery is discharged on each cycle, the shorter the battery life. Using
more batteries than the minimum required will result in longer life for the battery bank.
A typical cycle life chart is given in the Table 7.6:
TABLE 7.6: TYPICAL CYCLE LIFE CHART
Depth of Discharge
% of Ah Capacity
Cycle Life of Group
27 /31
Cycle Life of Group
8D
Cycle Life of Group
GC2
10
1000
1500
3800
50
320
480
1100
80
200
300
675
100
150
225
550
NOTE: It is recommended that the depth of discharge should be limited to 50%.
7.15 INSTALLING BATTERIES - SERIES AND PARALLEL CONNECTION
Batteries are normally available in voltages of 2V, 6V and 12V and with different Ah
capacities. A number of individual batteries can be connected in series and in parallel to
form a bank of batteries with the desired increased voltage and capacity.
SECTION 7 |
General Information - Battery Related