Originally Posted by Hoo Dad
Can I replace with a 12.8 volt automotive light? Will the light be dimmer or brighter? Why are some bulbs 12.0 volts and others 12.8 volts? I have researched and can't find an answer. Auto store employee didn't have answer either.
12.8 volts is the average that a fully charged 12 volt battery has. Here is an explanation of different types of bulbs, bases, and stuff. Another one for Herk's/Lou's ever expanding library.
Miniature bulb, Miniature Bulbs, Miniature Lamp, Miniature Lamps, P13.5S, miniature flange base, Single Contact Bayonet Base, Double Contact Bayonet Base, Candelabra screw base, Festoon 8mm, SV7mm Base, Festoon 10mm, SV8.5mm Base, 2 pin base, miniatu
This is an excerpt from the link that helps explain it some:
Next in importance is voltage identification. Voltage is electrical potential while amperage is the flow or current of that electrical potential. Typically voltage and amperage is stamped on the base of the bulb. Wattage is calculated by multiplying voltage and amperage. If your bulb is stamped with 12v and .1A you may multiply 12*.1=1.2 Watts.
There is some margin of error with voltage but ideally it should be as exact as possible. It is always better to order a slightly higher voltage than a slightly lower voltage. Typically bulbs are designed for a slightly higher voltage than the anticipated power source. For example, household bulbs are generally rated at 120 or 130 volts while the voltage coming out of your wall socket is only 110 Volts. A 130 volt bulb will have a heavier filament than a 110 volt bulb and will last much longer. Similarly automobiles have a 12 volt battery yet many automotive bulbs are rated at 12.8 Volts.
In summary if you cannot find a bulb with the exact voltage stamped on your bulb you will be OK with a bulb with a slightly different voltage. A bulb rated with a slightly higher voltage will not be quite as bright but last longer or a bulb with a slightly lower rated voltage will burn brighter but not last as long. Using too low of a voltage bulb i.e. a 24 volt bulb in a 110 volt lamp will result in the bulb burning out almost instantly while using a 120 volt bulb in a 24 volt lamp will result in a very, very dim bulb that will last a very, very long time.