The need of battery in a vehicle

When vehicle or car engine is at rest and in stop condition, the only power source you have to crank the engine initially from standstill is the vehicle battery. At starting the self-starter motor draws several hundred ampere of current from the battery. The current draw depends upon the engine condition, size of the engine and temperature of the engine. The new and high compression engine needs more power to crank it hence more amperes the self-starter will draw. An old and worn out engine have less compression so the self-starter needs less current to crank it. Size of the engine also matters. A big size engine needs more amperes on the self-starter to crank it. Same is true for a diesel engine. As diesel engine have bigger size, much more compression and more accessories attached to it compared to a gasoline or petrol engine of the same capacity and capability. The temperature of the engine is another parameter in self-starter current draw. In cold weather the oil in the engine becomes more viscous and it offers more friction to rotation. So it is difficult for a self-starter motor to rotate a cold engine compared to a hot engine.

When vehicle or car engine starts, its alternator spins with engine and produces electricity to charge the battery and also it powers up all the accessories and systems on a vehicle or car. Normally alternators on a vehicle produce current from 50 to 160 amperes which is considered to be sufficient for almost all needs and requirements on a vehicle. But sometimes needs arrive when some heavy load needs to be operated on a vehicle and demands arise when huge amperes are required to fulfill that requirement. In this condition the vehicle battery supplied the extra amperes to meet the requirement. This is especially is the case when vehicle is idling and all the accessories are switched on.

There is another requirement on the modern cars when the key is at off position and engine is stopped, even the systems on the vehicle consume little current to keep the systems up. These include immobilizer, auto doors, proximity entrance, body computer, engine ecu, clock, stereo and cameras. These systems take little power to do some special functions and keep their memory. Usually they need as little as 40 miliamperes to keep such systems alive. But this small current draw also drains the battery in a week or more if the vehicle is not started periodically to charge the battery. So this is important to start the vehicle after certain time period to keep it in good running and starting condition. Another advice could be to loose one of the battery terminal if you are about to park the vehicle for long period of time. Another possibility could be the use of an external charger on the battery to keep the battery in charged state all the time you keep the car parked.

In case if the chagrining system of a vehicle fails, all the accessories and car engine current and electrical power requirements will be fulfilled by the battery and battery will provide power to all circuits including fuel pump, ignition system, fuel injection and some other circuits. In this situation the battery will power up everything up to certain level till the battery terminal voltage reduce down to a specified level at which the battery would be empty. This time is about two hours for most batteries supplying 25 ampere of regular current.

Battery power depends upon a few parameters. Those include plate size, no of plates, battery weight, plate material and quantity of electrolyte in a battery. These all parameters are dependent to each other. It is not possible to increase one parameter to get more power. Instead all parameters are battery design parameters and they are well calculated during battery manufacturing.