21-08-2018, 05:38 AM
This topic is extensively covered on the old website. Several gave full details for simple conversions. Several more gave incomplete information so that the conversions seemed to effectively defy physical laws. Other conversions were more complex with (dubious) use of mechanical volt regulators, or more appropriate electronic regulators. As the original field winding is intended for just 4 or 5volts it is easy to cook. And, esp with the supplied field current not apparent on the ammeter, easy to exceed the safe total armature current and cook that too, as so many have been. Some 12v conversions I have seen are used for little more than ign current with the battery bench charged. Whatever, cars are rendered non standard and unless documented and kept with the car, become a puzzle for many, including auto electricians, already baffled by the 3rd brush. The most refined conversions as above combine 2 brush operation and electronic regulators, and the best of these have rewound field windings .
A major advantage of 12v is cheaper more readily available batteries and modern regulated bench chargers for.
As others have pointed out, many Sevens were used for general running including extensive at night. Modern brake lights and modern traffic holdups as at lights are a drain but the engine can be kept mildly revving. and headlamps turned off. A fundamental problem is that original 18w 6v headlamp bulbs are not available or considered too feeble so cars are run with larger bulbs. If ammeter max with lights off is limited to safe 8-10 amps the battery will then discharge at night. But you can still go a long way. (in emergency one lamp can be disconnected!)
For those with minimum electrical savvy much to be said for the original with charge rate kept within the recognised limit.
A major advantage of 12v is cheaper more readily available batteries and modern regulated bench chargers for.
As others have pointed out, many Sevens were used for general running including extensive at night. Modern brake lights and modern traffic holdups as at lights are a drain but the engine can be kept mildly revving. and headlamps turned off. A fundamental problem is that original 18w 6v headlamp bulbs are not available or considered too feeble so cars are run with larger bulbs. If ammeter max with lights off is limited to safe 8-10 amps the battery will then discharge at night. But you can still go a long way. (in emergency one lamp can be disconnected!)
For those with minimum electrical savvy much to be said for the original with charge rate kept within the recognised limit.