not more "electricity" so to speak
you'll still not have more than 12 volts but the reserve will be there

Found this at Optima's site regarding battery runtime and "amp hours":

The D34/78 is rated for 55 amp hours and 120 reserve minutes, so one battery will yield 2.75A steadily for 20 hours (55 amp hours divided by 20) before reaching 10.5V and being classified as "fully discharged." It will carry a 25 amp load for two hours before needing to be recharged.

It's been a while since I messed with electrical circuits, but they are similar enough to pumps that I can keep up somewhat... Adding batteries in parallel would provide more amps at the same voltage, right?

i think you are right gonk(i'm not gonna pretend to "know something" if i'm not sure)
but i'm doing it all for reserve in my truck i have an 160 amp alternator that cannot power the truck and stereo so, basically they provide the ooooooommmph for a peak (reserve)i was sold on my amps because the are "unregulated" whereas if you can put more in you get more out (to a limit of course)

it's amazing gonk, i'm talking about 160 amps here and you are on another thread talking about 15 amps!
how can there be such a difference between the home and car power requirements.
this is a good question if somebody really knows(and don't say cabin gain 'cuz if there is such a thing then why do i have to have 4 times as much in my truck compared to home in something 1/20 of the size)???

In the case that theendofday is considering, there is not an alternator available to provide that baseline 160amp flow (unless he runs power in from his car and leaves the engine running), so he would be using the batteries in parallel to produce all of the current for the system. If we take a trio of batteries in parallel, that would be either an 8.25 amp load for 20 hours (which wouldn't offer much) or up to 75 amps for only two hours. For brief demos in a store, that would probably be pretty effective - running at a very low level for most of the day with brief spikes up to a very high level would probably not drain the batteries until near the end of the day. For use in a 5.1 channel home theater, it may be fine for prolonged two-channel listening or watching TV at moderate volumes, but you may also find yourself stopping at the end of the first disc of the extended edition of Return of the King to recharge batteries before continuing with the second disc.

i spoke too soon,i went out to have a smoke and started thinkin' DC and with the wattage and current ratings out of my home amp it kinda collaborates with my car amps

You're looking at amps at two different voltages. We're looking at 15A when it comes in at 120V, but with home theater equipment we don't really track how many amps may be zipping around downstream of the transformer or really even what voltage it's at (although the equipment's designers certainly do). In a car, you don't have 120V, you have 12V, so to achieve the same power (watts) you have to increase the current (amps) by a factor of 10.

Think about it this way - your 160A alternator is operating at 12V, while the outlet behind your entertainment center is connected to a 15A circuit breaker and is operating at 120V. The two are capable of providing roughly the same wattage - 1800W for the outlet inside, or 1920W in the car.

ok that helps!

gonk, good explanations. This topic has really gotten going here.

Do you guys seriously think he should use the batteries? How is he going to recharge them? I thought this setup was supposed to be an HT setup. Meaning he should be able to just plug it in and only have to turn it on and off, basically. Besides the tweaking of the settings he'll need to do I mean.