I was curious about the amount of equipment (amps) one standard size 12 volt car battery can handle?
How many licks does it take to get to the center of a tootsie pop? I'd say both questions will have similar answers. 
BTW, when the vehicle is running the amplifiers are supplied power from the alternator, not the battery (assuming the electrical system isn't overtaxed). For the most part the purpose of a battery is to provide power when the vehicle is off, and to provide power to start the vehicle.
Use one good, high quality battery as part of the power supply for daily driver systems. A battery will last about 3 years if not repeatedly taxed strenuously (allowed to discharge to the point where it has to be recharged to start the car). Numbers of amplifiers has no bearing on it at all. Life is shortened with abuse of equipment.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
ok sorry guys let me rephrase...
So, i an installing a system into my wakeboarding boat. My total system will include a 4 channel 60rms @4ohm and a 4 channel 75rms amp and a mono 300rms @4ohm... and a deck but i dont think that is a very big draw. I am running a 4aug cable to a dist. box (both for ground and +) and using 8aug cable to each amp. I understand the alt keeps the battery topped off while the engine is running but my consern was for when the engine is off. I honestly dont know what brand battery i have. I hope that helps.
That will depend on the current capacity of the battery and how much total current the system draws. If you are worried about it, you can always add more batteries to the system, isolated from the main battery of course so you don't drain all your reserve power. Usually boats have dual battery setups anyway with a switch. If you can spend a little more money, there are some great deep cycle batteries on the market like Kinetic's largest model.
I understand you are asking about your boat and I will answer that question in a second, but I do want to make one point clear. You said:
canthink344 wrote:
I understand the alt keeps the battery topped off while the engine is running but my consern was for when the engine is off. .
No, the alt in a car of truck supplies ALL the electrical loads of the car, the engine, and any additional things you've added like sound systems, AND keeps the battery charged. The battery in a running vehicle will not be used unless the alt cannot keep up with the load, and then it indicates you need a larger alternator. I just don't want anyone reading this thread to get a wrong impression.
As to your battery load question, you need to know the ampere-hour rating of the battery (NOT the crank amp rating) and the total ampere demands of your system. For example, if the battery is rated at 40 Ah and your total system load is 40 amps, the battery should sustain this load for one hour. Assuming it is brand new and fully charged.
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