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BATTERY SIZING CALCULATION.

We believe in educating a customer and winning his confidence. In such a step towards educating our customer, we are giving the battery sizing calculation to enable the customer to really get true value for his money.



MAXIMUM BATTERY DISCHARGE CURRENT( I dc) - 
                      UPS CAPACITY  * POWER FACTOR      /
   --------------------------------------------------------------------------------------------------------
     MINIMUM INVERTER EFFICIENCY* BATT CUT OFF VOLTAGE
THEN THE AH OF THE BATTERY IS ARRIVED BY MULTIPLYING THE CURRENT (Idc) WITH THE VALUES GIVEN IN THE TABLE.  THE AH ALSO CAN BE CALCULATED FROM THE BATTERY (TIME Vs DISCHARGE CURRENT) GRAPHS.
EXAMPLE: 5KVA WITH 12 BATTERY SYSTEM.
(KINDLY ASK THE VENDOR ONLY TWO THINGS - UPS CAPACITY & NO. OF BATTERIES AND APPLY THE ABOVE FORMULA TO GET THE AH.)
I dc  =    5* 1000 * 0.8   /    0.9 * 126
LET US UNDERSTAND THE FIGURES WE HAVE PUT IN.
5KVA IS 5000VA, POWER FACTOR FOR BATTERY SIZING IS ASSUMED AS 0.8, MINIMUM INVERTER EFFICIENCY IS TAKEN AS 90%(0.9) AND BATTERY CUT OFF VOLTAGE IS 10.5 VOLTS PER BATTERY * 12(NUMBER OF BATTERIES)
AGAIN,  I dc  =  5000*0.8 / 0.9* 126   =  4000 / 113.4   =  35 amps.


THEREFORE AH  =  I dc   *  K ,  K = A CONSTANT.
(K = 1 FOR 30 MNTS BACK-UP, = 1.6, FOR 60 MNTS,  =  2.5 , FOR 120 MNTS,  =  3.5 , FOR 180 MNTS, = 4.5, FOR 240 MNTS, FOR SMF BATTERIES.

THUS FOR EXAMPLE 12 NOS - 12V- 35AH (40AH IS THE NEAREST CAPACITY AVAILABLE.) IS REQUIRED FOR 30 MNTS BACKUP AT FULL LOAD. LIKE WISE YOU CAN CALCULATE FOR OTHER BACKUP TIMES.
ALTERNATELY, YOU CAN ALSO CALCULATE THE BATTERY AH RATING FROM THE BATTERY( TIME Vs DISCHARGE CURRENT ) GRAPHS GIVEN ON THIS WEB SITE.( http://www.aarbeeenterprises.com/specification.html).

THE PROCEDURE, CONSIDER Idc ON X - AXIS AND THE BACKUP TIME DESIRED ON Y-AXIS. THE INTERSECTION POINT IS THE AH REQUIRED.
KINDLY FEEL FREE TO SEEK ANY FURTHER CLARIFICATION
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