The generator set shall be provided with an electric starting system. The electric starter motor for the engine shall be of automatic type to be controlled by the automatic starting and stopping system. Unless otherwise specified in the Bill of Quantities and/or Drawings, each engine shall be fitted with its own electric starting system complete with batteries and battery charger.
Unless specified otherwise, batteries shall be 24 volt heavy duty nickel cadmium (Ni-Cad) batteries, each cell of 1.2V nominal and of C5 rated capacity. The capacity of the batteries shall be as recommended by the battery manufacturer for a particular make and model of the generator set offered plus that required to operate the dc indicating, tripping, alarming and control circuits. The batteries shall be of sufficient capacity to provide a minimum of six (6) successive
abortive starts of the engine without recharging. The minimum cranking period for each abortive start shall be 15 seconds. The Tenderer shall ensure and guarantee that the capacity offered in the Tender shall meet this requirement. If so required by the S.O.’s Representative, the Electrical Contractor shall submit calculation worksheet together
with all battery data and characteristics on the sizing of the batteries to meet the requirements. In the case where the capacity of the batteries offered in the Tender fails to meet the requirement, the Electrical Contractor shall responsible to provide at his own cost the batteries of sufficient capacity that satisfy this requirements. The batteries shall be connected to the starter motor starting and stopping circuit complete with indicating or signal devices. A double pole isolating switch of suitable rating shall be provided between batteries and the starter motor. Batteries shall be housed in a rack or crate located beside the generator set and the exposed battery terminals shall be protected by insulation cover to prevent accidental shorting of the terminals. The battery rack or crate shall be strong, adaptable and provides good alkali protection. Low battery voltage protection shall be provided so that an alarm signal is given and engine starting system is cut off when the battery voltage falls below the required voltage for starting the engine.
12.2 BATTERY CHARGER
A battery charger shall be provided and installed for the generator set used in standby operation mode. The battery charger shall be of automatic constant potential current limiting type with two rates of charging, suitable for operating at an ambient temperature range of 25 0C to 40 0C, complete with ammeters (milli-ampere meter for trickle charge and ampere meter for boost charge), voltmeters, mains isolator, indicating lights for ‘Mains On’, ‘Trickle Charge’, ‘Boost Charge’, ‘A.C. Failure’ etc. The battery charger shall be of the type and make recommended by the battery manufacturer. The charging rates shall be in accordance with the battery manufacturer’s recommendations. The battery charger shall be suitable for charging nickel cadmium battery and lead acid battery. Selection of charging for nickel cadmium battery or lead acid battery shall be effected by means of a manually operated changeover switch installed inside the battery charger cubicle. Miniature circuit breaker (mcb) or high speed fuse shall be used at the input and output circuit for protection against excessive current flow. The charger components shall be protected against over-voltage during battery disconnection or in case of loose termination, and also against reverse battery connection. The battery charger shall also be fitted with surge protection devices to protect against voltage surge due to lightning. In addition the battery charger shall provide individual indication and common alarm under the following fault conditions:-
(a) DC low and high volt – ± 20% of float voltage
(b) Battery earth fault – positive or negative earth fault
(c) Mains failure – mains failure
(d) Charger failure – output voltage drops abnormally
(e) Load open – 5% of output rating
The battery charger shall be separately housed in a metalclad enclosure either wall mounted or floor standing type mounted near to the batteries. The cables connecting the batteries to the battery charger and to the engine respectively shall be of suitable size multi-strands copper conductor pvc insulated flexible type, installed in cable
trench covered with hot-dip galvanised checker steel plate. Where the generator set is used for continuous supply, an engine driven alternator of suitable current rating coupled to the engine for charging the batteries shall be provided and shall be supplied by the generator set manufacturer. Automatic cut-off shall be provided when the batteries are fully charged.