your completely right, not one word of what anybody has said has made any sense. except for the part where we all know what the voltage is (12v rounded off of course for simplicity for anyone who cant keep up with with the conversation so far) and i dont recall every seeing a power rating in Watts anywhere on the label of the radio, so to try to figure this out, we would have to do extra work to get that value, all while we know what the current limit of the radio is because there is a big red chunk of plastic hanging out side of the radio that does give us that information. then there is the finale bit of information needed the actual question at hand here, which is the variable... TIME
by knowing the voltage, current, and time, you should be able to answer the OP's question
also the most common ratings found for battery's (aside from Cold Cranking Amps, which wont help us with this problem) would be
Reserve Capacity (RC). This is the number of minutes a fully charged battery at 80 ° F will discharge 25 amps until the battery drops below 10.5 volts.
and
Amp Hours (AH) is a rating usually found on deep cycle batteries. If a battery is rated at 100 amp hours it should deliver 5 amps for 20 hours, 20 amps for 5 hours, etc.
also since it is much more common to see a battery's rating in amp-hours instead of watt-hours, why would we bother to try to figure any of this out in watt-hours?
lets try this again, for the sake of removing all theory, lets say that this was the exact same battery that came in his car (its close but not quite of course)
hmmmm. dont see a watt rating in there. i do however see that it has a reserve capacity of 100 mins.
well from above i know that the RC is how long a battery can provide a 25 amp draw for a 100 mins until it is down to about as low as you want to let it get before recharging. now i can either sit around and figure out math that wont help me with my problem or i can use the info i already have to know that 10A is less than 25A (by 2.5 times for those counting) and 2.5 times the 100 minutes is about 250 minutes that battery should be able to power up that radio (not too mention, at full blast ) which just happens to be a little over 4 hours as String had mentioned.
so now do you understand this topic?
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How long before X930BT drains the car battery?
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Believe me, you all can get Advance Auto Parts multiple at Discounted prices through Advance Auto Parts Coupons.