Samlex EVO Series Manual

22 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 23
Now, the capacity of the batteries is determined based on the run time and the usable
capacity.
From Table 1.9 “Battery Capacity versus Rate of Discharge”, the usable capacity at 3 Hour
discharge rate is 60%. Hence, the actual capacity of the 12V batteries to deliver 300 Ah will be
equal to: 300 Ah ÷ 0.6 = 500 Ah, and the actual capacity of the 24V battery to deliver 150 Ah
will be equal to 150 Ah ÷ 0.6 = 250 Ah.
And nally, the actual desired rated capacity of the batteries is determined based
on the fact that normally only 80% of the capacity will be available with respect to the rated
capacity due to non availability of ideal and optimum operating and charging conditions. So the
nal requirements will be equal to:
FOR 12V BATTERY: 500 Ah ÷ 0.8 = 625 Ah (note that the actual energy required by the load
was 300 Ah).
FOR 24V BATTERY: 250 Ah ÷ 0.8 = 312.5 Ah (Note that the actual energy required was 150
Ah).
It will be seen from the above that the nal rated capacity of the batteries is almost 2 times
the energy required by the load in Ah. Thus, as a Rule of Thumb, the Ah capacity of the
batteries should be twice the energy required by the load in Ah.
1.14.15 Charging Batteries
Batteries can be charged by using good quality AC powered battery charger or from alternative
energy sources like solar panels, wind or hydro systems. Make sure an appropriate Battery
Charge Controller is used. It is recommended that batteries may be charged at 10% to 20%
of their Ah capacity (Ah capacity based on 20 Hr Discharge Rate). Also, for complete charging
(return of 100% capacity), it is recommended that a 3 Stage Charger may be used (Constant
Current Bulk Charging followed by Constant Voltage Boost / Absorption Charging followed by
Constant Voltage Float Charging).
SECTION 1 | Safety Instructions & General Information