Parameter of batteries

1. S.Gomathy M.E.,M.B.A
Parameters of Batteries
S.Gomathy
Assistant Professor
Department of EEE
Kongu Engineering College

2. S.Gomathy M.E.,M.B.A
 The characteristics of batteries are defined by a set of battery
parameters.
 These parameters include charge storage capacity, terminal
voltage, rate at which batteries can be charged and discharged,
the cost of battery, the number of times the charging-discharging
cycle can be carried out in a battery lifetime and so on.
 Ideally, we would like our battery to work for many years and
should give us required energy in all conditions.
 Based on the parameter values mentioned by the manufacturer, the
selection of a battery can be made.

3. S.Gomathy M.E.,M.B.A
The standard parameters of a battery specified by the
manufacturers are following:
 Battery terminal voltage (in volts),
 Charge storage capacity (in Coulomb or ampere-hour or
Ah),
 Depth of discharge (in percentage),
 Number of useful charging-discharging cycle (in number),
 Life cycle (in years),
 Self discharge (in %), etc.

4. S.Gomathy M.E.,M.B.A
Battery Terminal Voltage (V)
 The electrical energy transfer from battery to load is possible only when
there is voltage difference between two terminals.
 A battery’s terminal voltage is the voltage difference between its two
electrodes.
 The voltage difference between the battery terminals is driving force for
current to flow.
 For solar PV system applications, there are batteries which are available
with 6 V and 12 V ratings.
 Each battery is made up of cells.
 The terminal voltage of cells is determined by the material they are made
up of.

5. S.Gomathy M.E.,M.B.A
 Normally, the cell voltage is not large to give us required 6 V
or 12 V
 Therefore, many cells are connected together in series to get
higher voltage.
 In a 12 V Lead-acid batteries, 6 cells are connected together.
 The battery terminal voltage changes with the condition of
battery.
 The terminal voltage increases when battery gets charged, the
terminal voltage decreases when battery gets discharged.

6. S.Gomathy M.E.,M.B.A
Battery Open Circuit Voltage and Terminal Voltage
 The terminal voltage of battery is maximum when it is fully
charged and when no current is flowing. The condition of no
current flow is equivalent to open circuit.
 The maximum terminal voltage of battery is also referred as open
circuit voltage of battery or Vo.
 When current flows through battery, its terminal voltage is normally
lower than the open circuit voltage, Vo.
 This happens because of the internal resistance of the battery.
 Due to its own resistance, some voltage drop occurs inside the
battery.
 This voltage drop is equal to the current flowing through the battery
multiplied by the internal resistance of the battery or equal to I × Ri

7. S.Gomathy M.E.,M.B.A

8. S.Gomathy M.E.,M.B.A
 The battery has its internal resistance due to many factors.
 The factors like the contacts within the cells, metal plates/electrodes
and salt bridge/separator, even the electrolyte creates some internal
resistance.
 Open circuit voltage of a battery is higher than the terminal voltage
under usage due to internal resistance of batteries.

9. S.Gomathy M.E.,M.B.A
Terminologies for Battery Terminal Voltage
 Open circuit voltage:
 It is also called theoretical voltage because this is the maximum possible
voltage at output terminals of battery when circuit is open.
 Nominal terminal voltage or operating voltage:
 It is actual voltage available at the output terminals of the battery on which
load can operate. The standard battery nominal voltages available are 1.5 V,
3 V, 6 V, 12 V, 24 V, 48 V, etc.
 Cut-off voltage:
 It is a voltage up to which the load can be operated and below which the
battery should be disconnected from the load in order to prevent it from
over-discharge.

10. S.Gomathy M.E.,M.B.A

11. S.Gomathy M.E.,M.B.A
Battery Storage Capacity (C)
 The capacity of a battery is the capacity to store the charge in the
battery.
 It is the product of current (in amperes) it can deliver for a given
time (in hours), i.e., Ampere × Hour (Ah).
 One ampere-hour (Ah) is the amount of charge delivered when
constant current of one ampere (A) is used for one hour (h).
The capacity of non-rechargeable batteries normally varies in few
mAh(milli Ah) to several Ah range.
The capacity of rechargeable batteries can vary from few Ah to
thousands of Ah.

12. S.Gomathy M.E.,M.B.A
 The capacity of batteries depends on temperature.
 The same battery will have different capacity at different
temperatures.
 The capacity is specified at standard test conditions of 25 °C.
 Hence, the capacity value measured at installation sites may vary
from the values given by the manufacturer because of the change in
temperature at particular location.
 Therefore, while selecting the battery for a given purpose,
temperature of the location should be taken in account.

13. S.Gomathy M.E.,M.B.A
Thank You