02-11-2017, 10:20 PM
To bench test a dynamo I use a piece of 1/2" square bar with one end turned to 1/2" diameter to fit my electric drill and the appropriate socket to fit the drive gear nut on the other end. The dynamo is securely clamped in a vice with and you need to hold the drill very firmly otherwise it could end up on the floor. You may need a jubilee clip on the drive shaft to stop the socket migrating towards the drill and if it's a reversible drill make sure it drives the dynamo clockwise looking on the drive gear end. At about 2500 rpm I find a standard dynamo in good condition generates between 15 and 20 volts depending on how much grunt the drill has.