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Old 05-13-2008, 07:42 PM
al_cam al_cam is offline
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Join Date: Jul 2006
Location: Melbourne Australia
Posts: 5
Giorgio,

Electrics for cars are usually designed to run at the alternator volts 13.5v - 13.8v, so you're not going to burn out the globes. You need to select a relay to handle the current the globes will draw. Watts as used by the globes is volts x amps, so divide your total amperage by the volts and get a higher amperage relay. Use one relay for both globes, so multiply the watts by 2. For example 150 w globe? 150x2=300W, 300w/13.8v=21.8A. You need a relay that handles more than that. Typical car relay is 30A. Although if you are getting close to the rated current for a relay, they tend to get hot and melt. If you were using globes higher than 150W each you'd be better off using one relay for each globe.
Al Campbell
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