What is the distinction between a cell and battery
Battery is 2 or more cells
Shelf life can be increased by storing a dry cell at low temperature
True
What is the difference between a primary cell and secondary cell
Secondary = rechargable
How long can a 1.5v cell supply a current of 60mA before reaching the cut-off voltage if the capacity of the cell is 5000mA-h
83 hours
5000/60 =83.333 hours
A voltmeter across the terminals of a cell shows a decreasing voltage as the current to a variable load increases, why?
Increased interval V, drop due to resistance
Ni-cad batteries may be stores in a charged or discharged state
True
Too many shallow cycles may cause a memory effect on a ni-cad cell
True
Three items of PPE when servicing wet cell batteries
Eye protection
Face shield
gloves
Rubber apron
What type of charge is given to a standby battery in order to maintain it in a fully charged condition
Trickle charge
What are two fundamental methods used for charging batteries
Constant voltage and constant current
Why is a diesel engine commonly used over others as an emergency generator
Long fuel life
Low maintenance
Less fire hazard
High calorific value
The emergency generator must match the normal power supply of the building in ___________ and ________
Voltage and frequency and phase
How long must E lights maintain
At least 30min
What device in a standby generator set is used to maintain constant speed under varying load conditions
Governor
Why is the output voltage of a generator varied by changing the field current rather than the speed of the prime mover
RPM changes, frequency and voltage
A bypass isolating switch used to allow servicing on an automatic transfer switch, which would best be described as
Make before break switch
There are four main categories for secondary batteries in the market today. What are they?
Automotive, portable, electrical vehicle, standby
Why should a lead acid battery not be left in a discharge state for a long period of time
Sulphation
lead to more internal voltage drop
