Preamble

The development of an ‘on-board’ rechargeable Battery in the ‘20s revolutionised the Electrical System of a Car and today, especially in the luxury segement, they’re as complex and sophisticated as in a passenger jet aircraft – deploying some kilometers of specialised wiring, relays and switches.

Electrical problems such as a flat battery or malfunctions of various sorts are probably the most frequent that plague an average motorist. So the sooner one understands the basics, the better for him and his car.

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Some Basics

Flow of electricity is somewhat akin to flow of a liquid/water in a stream, where ‘velocity’ of stream (kph) is equivalent to system ‘voltage’ (V) and the quantum of flow (cusecs) is eqvt to current in ‘Amperes’ (A). Further, an electrical ‘load’ is measured in ‘Watts’ (W) and in a DC system, it’s a product of VxA.

Battery

The fundamental requirement of a car battery is to provide reliable power to the ‘starter-motor’ to fire the engine under most adverse conditions – incl the essential auxiliaries that go with it such as the fuel pump/ignition system etc -such as sub zero temperatures, prolonged shut downs, poor state of engine health etc.

Therefore, a car battery is ‘sized’ accordingly i.e. higher the power required to ‘crank’ the engine, larger the Battery required. Such sizing goes in terms of ‘Ampere Hours’ (AH). Typically, a battery type ‘NS40S’ has an AH capacity of 30/20 hr. In other words, such a fully charged battery can deliver 1.5 Amps for 20-hrs.

It’s note worthy here that ‘A’ and ‘H’ are not always inversely proportional i.e. if such a battery is discharged @ 5 Amps, it’ll last < 6 hrs !

Alternator

Having got a suitable Battery on-board, it’s logical that it’d require an on-board ‘device’ to keep it charged too, as it gets substantially discharged every time the engine is fired. Till about mid-‘60s, this job was done by a ‘dynamo’ but as load demands increased on it, it was found wanting in more ways than one – such as inability to charge the battery at low/idling engine speeds and relatively short/unreliable life due to the ‘commutator’ it had to have, to convert the basic ‘AC’ it generated into ‘DC’ for use on board - coz the Batteries are DC only.

This need paved way to development of ‘Alternators’ that overcome all such deficiencies, where the wear-prone ‘commutator’ got replaced with a solid-state ‘Diode Bridge/Plate’ and its external electro-mechanical ‘Voltage Regulator/Cut-out’ got replaced with in-built (solid state) voltage regulator – to maintain the Alternator output within 12-15 Volts - as it’d otherwise vary with the engine speed just like the Dynamo.

Today’s average sedans have Alternators with an output capacity of ~ 60 Amps/15 Volts a/a 20 Amps of Dynamo’s of yore and are so designed that they’re able to meet practically all the ‘designed’ electrical loads of a car while on the move, including while idling at traffic lights with AC, Wipers, Headlamps etc on, and yet have required spare capacity to keep the battery fully charged at all times.

Having got an over-view of a car’s basic electrical system, here’re some Do’s and Dont’s to keep them trouble free :

Do’s

? Keep a regular check on the electrolyte level in your battery. Top-up to ‘max’ level, as and when required, using ONLY pure/battery grade distilled water. Overfilling is to be avoided at all costs as the electrolyte/acid will spill over when the battery is getting auto-charged and thus ruin its adjoining areas for good.
? Even the present day ‘maintenance free’ batteries require such attention ~ every 3-6 months and the ‘semi-sealed’ ones once a year or so. Keep its terminals free of sulphate’ deposits and lightly smeared with petroleum jelly.
? Likewise, it’s important to keep an eye on the Alternator drive belt tension since belts tend to loosen with age/mileage. A loose belt can lead to a flat battery after a while, for no fault of the Alternator.
? Switch-off headlamps at night in b2b traffic but leave the parking/tail lights on – wherever possible.
? This way, an OE Alternator can last ~ 50 kkm+ and well branded Batteries ~ 3-yrs+ before needing any service/attention. As and when needed, entrust the work ONLY to their Authorised Service Centres.

Dont’s

? It’s highly inadvisable to retro-fit any electrical accessories on present generation MPFI Cars, such as music systems, fog/rally lamps, high wattage head lamps, remote/central locking, fancy lights/horns etc that are not ‘OE/Dealer Approved’ and that too only by the Dealer and against a formal receipt. Otherwise, your OE Warranty and consequently the Insurance Cover stands to be annulled for having carried out ‘unauthorised’ modifications.
? This is of vital importance in present day ‘Mpfi’ petrol and eqvt diesel cars as no chopping/splicing/taping of the car’s original wiring harness is permissible; as otherwise, the on-board engine management ECU can mal-function or even fail for good and thus leave you fielding related problems for rest of the car’s life.
? It’s commonly advised out of ignorance even in prominent Media that using ‘relays’ for retrofitting high wattage accessories will solve the problem. Nothing could be farther from truth as – a) this’d inevitably involve tampering with the OE Wiring Harness that’s a taboo for reasons as above and b) any relay is just a ‘passive’ switching device that can only increase the load switching ‘capability’ of the OE switch and therefore, the additional electrical load in terms of Amps/Watts has to come from the OE Battery and in turn the Alternator only.
? The present day cost-competitive ‘edge’ designs leave hardly any room for such overloading, including the OE wiring. In plain speak, it’s asking for trouble – relays or no relays.

? Few vitals of a car like the Starter, Horns and to some extent, the Brake Tail Light Bulbs, like the household Mixie, are NOT ‘continuously rated’, as their application doesn’t warrant so. In other words, cranking a starter repeatedly for more than 5-secs at a stretch can considerably shorten its life along with that of the Battery. Same goes for Horns and they should be ‘tooted’ only in short bursts. Likewise, don’t rest your foot on the brake pedal when parked or waiting at traffic lights. Instead, shift to neutral if engine is running and engage the parking brake fully.

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