Whist we can supply a wide range of standard and upgrade alternators, we specialise in the small lightweight 50amp alternators that we convert to two wire operation to make replacement of a dynamo simple or minimise the wiring for installation into a kit car or race car.

One of the smallest alternators on the market and fully self contained all that is required is a connection to the battery and connection to a warning light. A single fixing point and single adjuster mounting also makes installation an easy task in almost every application. The alternator can rotate in either direction and low switch on speeds means it can be located in a variety of locations and driven from any part of the transmission train in addition to the conventional installation.

Typical fitting instructions                                                                  Typical data

If you currently have a Lucas dynamo fitted you will probably getting a maximum of 25 amps. You will see from our typical power graph that you can exceed this maximum dynamo output with the alternator rotating at 1500 RPM (typically just over idle speed of the car) so a 50 Amp alternator will be a vast improvement over the dynamo, otherwise you may need to know how to go about;


Calculating alternator size.

An alternator should be sized at 1.25 to 1.5 x total required current. To calculate this you need to add up all the power requirements of continuous and prolonged loads. Most equipment will give the rating in Watts on a data plate or it can be obtained from manuals or instruction books. Continuous or prolonged loads should include things like fuel pumps, cooling fans, ignition and injection systems. Then you need to add up all the intermittent use items such as lights, wipers and heated rear screens. You could include also things like radio or phone charges in either camp depending how you use them.

For the intermittent items take 10% of the total and add it to the full total of the continuous use items. Divide the total Watts by 14v and you have the required amperage. Multiply this by 1.25 or 1.5 and you have the size of alternator required. For example, if you calculate the total power required to be 500 Watts; 500/14 = 36 Amps. 1.25x36=45; 1.5x36=54 so an alternator between 45 and 54 Amps will be the correct selection.


Two thirds of all alternator failures are due to a faulty or weak battery. Batteries should be replaced every 3 years with the correct size for the vehicle. The next largest cause of failure is down to poor electrical connections, fuseable links or bad cables. Measure the voltage at the alternator terminal and at the battery, if the voltage drop is more than 0.5 Volts check the joints and cable of damage or wear and if necessary fit a new or larger cable. It is important if installing a new alternator to check the unit is getting a good earth, particularly if the engine or mounting brackets have been renovated and painted or powder coated. Disconnecting an alternator from the battery whilst it is running is almost always going to be fatal. The balance of alternator failures are split between faulty or improperly adjusted fan belts and jump starting another car improperly. Follow the instructions for jump starting In both the car hand books as it can damage other electronic equipment or motoring organisations have helpful instructions on the Internet.

Updated 18 July 2017