Read the previous answer, then mine, i think what you are looking for is how large of an inverter can you connect to a 12 volt battery, well, it depends on the source of power for that 12 volt battery, every battery is designed for so many volt hours, if you are charging with a solar panel, connected to a car alternator, or a wind generator, you will be limited by the charging rate, i often use a 1200 watt power inverter to power tools, i connect to 12 volt battery connected to 2 solar panels, i can run a small tv all day, or a power saw for 30 minutes, i hope this will give you an idea of what you are asking. If in a car, you can run 3000 watt inverter while the auto or truck is running to power just about whatever you want
7 months ago
Last edited at 5:14AM on 8/1/2013
Based on your comments to Bulldozier, you want to know how you can use a 900 watt audio amp with 300 watt speakers. This has nothing to do with volts, its all amperage everything you have will be working at 12 V. At 12 volts, 900 watts draws 15 amps, which is a pretty big draw for a car battery. Basically, the amplifier is rated at its peak output and does not produce 900 watts except when at full volume, so all you have to do is keep the volume down; this limits the amperage output and the speakers will be fine.