How long can a car run on battery power?

Has your alternator broken down? That doesn't mean that the car won't be able to drive at all. The only question is how many kilometres a car can travel on battery power alone. How many kilometres can a car travel on battery power? The answer depends on many factors: operating conditions and the availability of additional power consumers.

Appliance energy consumption

The electric battery, as a power source, is designed to operate independently. The generator is not switched on immediately after the engine is started. When the engine is started, the electrical power for the appliances comes only from the battery.

The duration of operation without additional charging depends on external circumstances and on the condition of the battery. The former can include weather events, the number of electrical appliances and the current they draw. How much power is consumed will be influenced by the level of charge in the battery at a given time. The same car will travel a different distance with all the appliances switched on. The energy consumption figures are quite different and should be based on the freshness of the battery.

Electricity consumption. The minimum is when the battery is new, the maximum – when the battery is nearing the end of its life.

Power consumption is the minimum when the battery is new, the maximum when the battery is nearing the end of its life.

How many kilometres can a car drive without a generator

To calculate the distance a car can travel, you need to know its design and basic parameters. The main indicator, from which you should proceed in the calculation – capacity, it indicates the permissible load and corresponds to the litre of the motor. This figure is always indicated on the battery label.

The capacity of a passenger car is from 55-75 A*h, it is higher for a lorry. The sign on the label is +25°C. You can use this number to determine the current at which the battery will be completely discharged within 20 hours.

Capacity of a passenger car is 55-75 A*h.

The number – specified by the manufacturer is nominal, it varies within 80– 110 per cent of it. Let's look at an example. The capacity is 55 A*h, the battery will discharge in 20 hrs. 55/20=2,75 Ampere. When making a calculation, it is necessary to take into account the electricity consumption of the battery. There is a constant load, which cannot be avoided. Whereas it is quite possible to switch off headlights, seat heating, tape recorder. It is also necessary to take into account the speed of the motor. In order to get the correct result, it is necessary to sum up the electricity consumption of all consumers.

How to calculate battery life

As an example, let's take a car with an injector engine and a capacity of 60 A*h, with headlights on, fan on, time of year – summer. The total consumption is approximately 15 Amps. Constant consumption – 8 Ampere. Figures appeared taking into account the injection system, which is – 4 Ampere, if the carburettor system will be taken into account – the figure will be reduced to 2.5 Ampere. The total current is – 23 Amperes. The running time is calculated by the following formula: 60/23=2.6 hours.

At a speed of 90km/h, the car will be able to drive 234km on a single battery. Attention! This result is only theoretical. It is necessary to take into account that the loss of electrical energy will increase dramatically during driving. These calculations are close for a battery in perfect condition, which is fully charged. It should be clear that the figures will be lower in winter.

What to do when the question arises: «To drive on one battery or not? »

In an emergency, you can count on the car travelling a short distance on battery alone. But it's best not to take any chances and have the road assessed if possible. Don't assume you'll be able to cover the maximum distance without problems, so find out where the nearest service station is. It's better to be reassured and think about how you'll get out of the situation if you're alone on an empty road away from people.

Be aware of an undercharged battery and frost when making calculations. You can measure battery voltage with a voltmeter. Switch off the battery. Figures from 12.2 V and less indicate a charge of less than 50%. The density of the electrolyte from 1.26 – 1.29 g/cm3. Here, a lower figure indicates a greater degree of discharge.

To be sure, you can take a spare battery with you or recharge the one you have. This option may not be suitable for everyone, of course.

What to do when your alternator fails on the road?

Prepare for such a breakdown is possible, we will talk more about this below. Now let's look at a situation where the failure occurs on the road. If you're lucky, you can get to the nearest service centre on battery power alone and solve the problem there. In the meantime, minimise all energy consumption as much as possible.

Do the following:

• Do not switch on the radio, tape recorder;
• Turn on parking lamps or emergency lights instead of headlights;
• Start accelerating slowly to reduce engine speed;
• Do not drive downhill.
• Roll down hills;
• Do not switch off the engine, so as not to waste energy on starting it later.

Important to know! If you manage to restart the car after it has stalled with the help of «cigarette lighter» of another car, after such a start the battery will not be able to work for a long time.

An important thing to know!

To avoid such unforeseen situations, it is important to carry out diagnostics of all systems of the car in time. The alternator can be checked on a stand. This will show you what condition it's in, saving you the hassle of travelling on the road.

The MSG MS002 COM Generator and Starter Diagnostic Stand is used to test 12 and 24 V car alternators. Using the stand in a car workshop will help to check the operation of starters and alternators up to 200 Amps, which means any cars and lorries. Stand MS004 COM checks starters and alternators up to 100 Ampere. The stands have different dimensions. MS004 COM can be placed on the work table of a car service technician.