Vehicle Electrical Charging and Starting Systems

Unit 48:

Level: 3

Guided learning: 60 hrs

Unit introduction

The application of electrical technology in modern motor vehicle systems is under constant development. This has resulted in an ever-increasing electrical load being placed on a vehicle’s charging and starting systems. The unit will give learners the opportunity to determine faults in a vehicle’s battery, charging and starting systems, identify and confirm the specific component that has failed and undertake suitable rectification procedures.

Learners will investigate the chemical process in a battery and understand how to specify a battery for a particular vehicle. They will gain an understanding of the operation and conversion of energy in the charging and starting systems of a modern motor vehicle. The unit will enable them to apply this knowledge to both charging and starting systems and undertake diagnostic and rectification work on a range of vehicles.

Note that the use of ‘e.g.’ in the content is to give an indication and illustration of the breadth and depth of the area or topic. As such, not all content that follows an ‘e.g.’ needs to be taught or assessed.

 

Learning outcomes

On completion of this unit a learner should:

  • Be able to specify a battery for a given motor vehicle application
  • Understand a vehicle’s starting system
  • Understand a vehicle’s electrical charging system
  • Be able to diagnose and rectify electrical system faults on a vehicle’s charging and starting

 

Unit content

 

  • Be able to specify a battery for a given motor vehicle application

Different battery types: wet/flooded – consists of all but freely suspended plates that are insulated from each other usually with the negative plate being sealed in a small polythene separator bag; Maintenance Free (MF) battery – normally a wet battery where the design keeps gassing to a minimum and includes a battery box that is sealed to keep the gases in place; Calcium-Calcium – where the antimony on both the negative and positive plates being replaced by calcium alloy; Valve Regulated Lead Acid (VRLA) battery – the battery box is designed as a small pressure vessel with safety valves; Gel – a Gel battery

has some elements, usually silicon compounds, added to the acid to ensure it gelatinises and thereby guarantee that no flooded acid can leak out; Absorbed Glass Mat (AGM (Vlies)) – keeps the acid in place by the separator paper that consists of a fibreglass mat operating like a sponge

Chemical processes of lead acid batteries: chemical to electrical conversion, water to electrolyte process, e.g. charge and discharge cycles, use of chemical symbols, changes to specific gravity and components chemical state; health and safety, e.g. gases produced, acid content

Battery performance and construction: performance, e.g. cold cranking amperage, amp/hour rating (10/20 rating); construction, e.g. casing, plates (lead dioxide and spongy lead), separators; connections, e.g. series/parallel, vehicle earthing, corrosion protection; electrolyte, e.g. sulphuric acid, distilled water; battery calculations e.g. amp/hour system requirement, cold cranking usage, plate area, maximum load; battery specification, e.g. manufacturer’s recommendations, type, make, performance; specify battery by comparing system calculations/performance tests to battery capabilities

 

  • Understand a vehicle’s starting system

Starting system: energy conversion, e.g. electrical to mechanical rotation, rotational to linear translation; starter solenoid, e.g. provide mechanical movement by use of Electromagnetic application; ignition key/push button switch, e.g. provide timely electrical supply to starting system; principles of starter motor, e.g. conversion of electrical energy to mechanical movement, creation and use of magnetic effect to create mechanical movement (Fleming’s left hand rule)

Starting system components: electrical supply (battery); circuit protection methods, e.g. fuse, immobiliser, key recognition, relay; ignition switch,

e.g. key or manual operation; wiring looms; warning system, e.g. visual and audible; solenoid; starter motor assembly, e.g. casing, magnets, armature, brush box, gear, roller clutch drive

Circuit diagrams: switched supply system; permanent feed system; recognition of circuit components/circuit symbols; types of circuit diagrams, e.g. use of workshop manuals, manufacturer’s diagrams, wiring diagrams and schematics

 

  • Understand a vehicle’s electrical charging system

Voltage generation, rectification and regulation: function of generator,

e.g. alternator to create electro-motive-force using Fleming’s right hand rule; system components, e.g. stator, rotor, rectifier, voltage regulator, slip ring, brushes, bearings, cooling fan; warning device; bridge rectifier; drive belts,

e.g. single- or multi- ‘V’ design

Multi-phase electrical output: principles of three-phase electricity,

e.g. excitation, magnetic inductance, sinusoidal pattern, full wave rectification; use of oscilloscope to observe wave patterns; AC-DC voltage conversion

 

  • Be able to diagnose and rectify electrical system faults on a vehicle’s charging and starting systems

Battery tests and faults: testing, e.g. relative density, battery capacity, condition testing; equipment, e.g. hydrometer, multimeter, dedicated test equipment, inductive amp clamp; typical battery faults, e.g. dead cell, shorting out, low specific density, failing under heavy discharge, physical damage (overcharged causing heat distortion, corrosion/degradation, mechanical damage/defects)

Starting system tests and faults: system operation; circuit testing,

e.g. continuity, feed, voltage drop; component test, e.g. ignition switch, solenoid operation, starter motor operation and internal components (armature, brushes, windings, circuit protection, e.g. relays, overload relay, immobiliser); use of test equipment, e.g. multimeter, dedicated test equipment, oscilloscope, inductive amp clamp; typical starting system faults, e.g. internal short on armature, failed solenoid operation, inhibitor switch failed

Charging system tests and faults: system operation; circuit testing,

e.g. continuity, feed, voltage drop; component test, e.g. diodes, bearings, rotor, windings; output test, e.g. voltage, current, waveform; typical charging system faults, e.g. diode failure (indicator light on), faulty voltage control (overcharging), bearing fault (noisy or excessive free play), faulty brush box/rotor (no charge); use of test equipment, e.g. multimeter, dedicated test equipment, oscilloscope, inductive amp clamp