BATTERY APPLICATIONS NOTES
CHOOSING THE RIGHT BATTERY
To calculate the battery capacity required for any application the current
draw and the time duration will be needed.
The following calculation assumes that the battery is dedicated to
domestic/auxiliary power and is not used for engine starting purposes.
The formula to arrive at the battery capacity required is :-
C = 2 x I x t
where C = Battery capacity in AHr
I = discharge current
t = Time for which the battery can sustain the discharge rate. (normally
expressed in hours)
example:- A battery is required that is capable of sustaining a discharge
rate of 25 Amps for a period of 2.5Hrs before the battery terminal voltage
falls below 11.5 volts.
using calculation above:- C = 2 x I x t
C = 2 x 25 x 2.5
C = 110AHr, from the list on the MAIN page the version BATTERY 3 would
be suitable for this application.
When using our range of Batteries to power DC-AC inverters such as our
range you need to select a bank size that will provide the necessary
sustained power. Consider this further example: you need to use a piece
of mains driven equipment rated at 100 Watts (a colour television and video
player), this will consume approximately 9.5Amps (watts divided by voltage
and this example the battery voltage, 10.5 volts, this allows for inefficiencies
of the inverter and any voltage drops on the low voltage input cables etc.),
assume that you need to run the television for 10 hours over 3 days (assuming
no recharge facilities available), this amounts to (using calculation above)
C = 2 x 10 x 9.5 // C = 190AHr. In this example a battery bank of 250/300AHr
is recommended. This figure does not include any power taken from the battery
for lighting etc.
We recommend that the following battery bank sizes for use with DC-AC
inverters where the batteries are used for supplying not only the inverters
but the normal 12 volts (24 volts) power as well.
OPTIMUM BATTERY SIZE
2 x BATTERY 3
4 x BATTERY 3 or 2 x BATTERY 5
2 x BATTERY 7
RECHARGING THE BATTERY
It should be noted that when recharging batteries in general it will require
1.2 times their discharge capacity to return the batteries to their fully
charged state. In most cases a stand alone alternator will not fully charge
depleted deep cycle batteries in a short period of time due to their charging
When charging our range of batteries it is recommended that if recharging
from a battery charger that a 3- stage charger such as our X-Calibre
is used or if the battery charger is not a smart charger that the output
voltage is set to 14.4 volts and is left connected until the float voltage
rises to 14.2 and then reduce the charging voltage to 13.8 volts.Our X-Calibre
3-stage battery charger will provide the correct charging routine
without manual intervention. Our range of alternator charge controllers
the 'X-ALT', 'X-PORT+' or 'Genie'
have special algorithms which cycle the batteries between 14.8 volts and
the normal float voltage of the alternator when in boost mode in order
to effectively fully recharge heavily depleted batteries in a shorter period
of time then stand alone alternators. By using this special algorithm and
not exceeding the maximum recommended charging voltage gassing (caused
by too high a charge rate) is reduced without extending the recharge period.
Our range of battery chargers the "X-Calibre"
has the correct charging voltages and 3 stage routine ideally suitable
for charging this range of batteries.
When considering implementing or replacing a battery bank it is normally
good practice to keep the battery bank to alternator ratio below 5:1, i.e.
for a 90A alternator the total battery bank should be 450Ahr, this is to
achieve a reasonable charge time period.
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