Battery Circuit Diagrams

Super starter for cars

The super starter makes it possible to start cars with ageing batteries and obsolescent (coil-based) Ignition systems, particularly during cold or damp weather. During starting, the voltage of an ageing (and possibly cold) battery will be insufficient for the coil to generate a tension high enough to create a strong spark across the spark plugs. The circuit presented ensures that the coil is powered by a 5attery of NiCd cells: even in these arduous conditions, such cells will last up to ten minutes. After the engine has started and the dynamo voltage has risen, the coil is powered by the car battery again.

The circuit uses the D+ terminal of the charging current indicator lamp (La1) to check whether the engine is running. since that terminal is connected directly to the dynamo. As long as the engine does not run, and the dynamo, therefore, does not generate a voltage, relay Re1 is energized via the ignition key (+connection) and the low-resistance dynamo (connection to earth).

The NiCd battery then provides plenty of power to the coil, irrespective of the state of a Car battery. Once the engine has started, a voltage will be generated by the dynamo. There is then no potential difference across the relay coil and its contact changes over, whereupon the coil is supplied by the car battery (or the dynamo).

Diode D1 prevents two possible troubles. First, it prevents the relay interrupting the current to the coil when its contact changes over, which would result in a spark at a moment that the engine does not need one. Therefore, the coil is powered via the diode during the change-over period. This reduces the voltage across the coil by about 2 V, but that does not matter. Secondly, it ensures that the car can be started when the car battery is fully charged and the NiCd cells are flat or have been removed for charging.

The relay must have a contact rated at not less than 8 A. Car relays with change-over contacts are not easily obtainable as a spare part, but can be often be found in car scrap yards (particularly in Citroen CX models). The Type FR606 diode may be replaced by a Type BYW29-100: both can handle currents up to 6 A and their reverse voltage is high enough to withstand the inductive peaks generated by the coil.

The circuit is best built in behind the dashboard, although it is advisable to place the NiCd cells in a removable holder to enable them to be charged externally. It is, of course, possible to charge them with the car battery via a suitable resistor. The D+ connection at the charging indicator lamp is that which is at earth potential when the engine is not running, but. the ignition is switched on. At the ignition switch is a cable that goes to the coil: that cable must be connected to the output. 15. of the circuit. The .® terminal of the circuit must be connected to the freed contact at the ignition switch. The -ye line of the circuit must be connected to the car chassis.

Super starter for cars Schematic diagram

 

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