part2
A battery with a capacity of 10 amp-hour should be able to continuously supply a current of 10 amp to a load for exactly 1 hour, or 20 amps for 1/2 hour, or 1/3 amp for 30 hours, etc., before becoming completely discharged.
Typical A/H Rating of Some Batteries:
Typical automotive battery: 70 amp-hours @ 3.5 A (secondary cell)
D-size carbon-zinc battery: 4.5 amp-hours @ 100 mA (primary cell)
9 volt carbon-zinc battery: 400 milliamp-hours @ 8 mA (primary cell)
The most common type of battery available is lead acid battery. A lead-acid cell generates around 2 volts. Small batteries contain 6 cells in a container which add together to give 12 volts at the terminals.
The steps to calculate the charger requirement for a battery are
i) Determine the suitable A/H ratting of the battery required according to the load and Backup as well as the charging time required
ii) Determine the recharge time required.
iii).To get the charging current, divide the A/H rating by that time.
iv). Add 20% to allow for the battery inefficiency.
v). If there is any additional battery load current during its charging like control circuit, add it also to the charging current.
vi).Select the next biggest charger in the range
Battery Voltage = 12
Volts Load Required = 700
Watt Efficiency Required = 90%
Total Battery Current = (700/0.9)/12 = 70 Amp
Estimated Additional Current = 1 Amp
Total Battery Output Current = 71 Amp
Battery Charging Current = 0.1 * 71 = 7.1 Amp
Backup Time Required= 2 Hour
A/H Ratting Of Battery = 2 * 71 = 141 A/H
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block diagram of UPS
AC TO DC CONVERSION
Type of chargers:
i). Ferro-Resonant Charger
They are very bulky because of low frequency magnetic control system in it. They are slowly recharged. Their magnetic field may disturb other components of the equipment.
ii). Linear Charger
They also use low frequency transformer in it to reduce the level of the ac voltage, then a combination of bleeding resistor, series resistor and a capacitor is used to control the current and voltage level of dc output.
iii). Switch Mode Charger
It is a newly technique, it directly rectify ac input, then this dc input is switched with high frequency through transistors and with the help of high frequency transformer, its level is lowered and rectified to desired dc output level
A/H Ratting of the Battery
Before designing the charger stage of the battery, we must see the A/H ratting of the battery, which determines the charger time as well as the backup time with respect to the charging current. The ampere-hour ratting ( A/H ratting ) is the indication of battery energy capacity, it is given by the relation:
A battery with a capacity of 10 amp-hour should be able to continuously supply a current of 10 amp to a load for exactly 1 hour, or 20 amps for 1/2 hour, or 1/3 amp for 30 hours, etc., before becoming completely discharged.
Typical A/H Rating of Some Batteries:
Typical automotive battery: 70 amp-hours @ 3.5 A (secondary cell)
D-size carbon-zinc battery: 4.5 amp-hours @ 100 mA (primary cell)
9 volt carbon-zinc battery: 400 milliamp-hours @ 8 mA (primary cell)
The most common type of battery available is lead acid battery. A lead-acid cell generates around 2 volts. Small batteries contain 6 cells in a container which add together to give 12 volts at the terminals.
Battery Charger Selection:
The steps to calculate the charger requirement for a battery are
i) Determine the suitable A/H ratting of the battery required according to the load and Backup as well as the charging time required
ii) Determine the recharge time required.
iii).To get the charging current, divide the A/H rating by that time.
iv). Add 20% to allow for the battery inefficiency.
v). If there is any additional battery load current during its charging like control circuit, add it also to the charging current.
vi).Select the next biggest charger in the range
Calculations:
Battery Voltage = 12
Volts Load Required = 700
Watt Efficiency Required = 90%
Total Battery Current = (700/0.9)/12 = 70 Amp
Estimated Additional Current = 1 Amp
Total Battery Output Current = 71 Amp
Battery Charging Current = 0.1 * 71 = 7.1 Amp
Backup Time Required= 2 Hour
A/H Ratting Of Battery = 2 * 71 = 141 A/H
NEXT
About the Author
I am Kashif Mirza, the founder of Student Training Lab (STL). I am working on projects since 2005 before that I just search things and now I am sharing my knowledge through this plateform.
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