Any math guys out there?
 

I don't know but is there a way to figure out approximately how long a battery will last at a given usage?I have built a system for a friend's party boat(tug) and now I need to power it.I have a class d amp running about 400 watts@ 6ohms and a 100x2@8ohms.How can I get it to last as long as possible for as cheap as possible before starting and recharging?I'm a newbie.

wait for other replies but im thinking a yellow top battery (the deep cycle one) would be most beneficial here

I was thinking maybe a couple but want to make sure.They can be charged from a charger and generator at the end of the night but still would like some good playing time

Yes there is.
You'd have to find the total current draw on your battery.
Once you have that you need to check the ratings of your battery, the AH is what you are looking for.
So let's say you are drawing 40 amps from your battery.
Your battery is rated at 80AH.
That means it can supply 1 amp for 80 hours, or 80 amps for 1 hour.
In this case the battery would last 2 hours.

Then what?Do i recharge?and will this last long or do they die from being drained and recharged?

sorry,and does that mean if I were to run 2 80ah batteries I'd get 4 hours?

Keep in mind, the voltage will also be dropping during that time frame. A voltmeter would be a good idea, as well you may want to think about keeping a spare battery tucked away....:smilie_da

That way you have 2 to run the system during the main part of the evening, and the spare in case you decide to stay out a little longer.....:smokin:

Which means that as voltage drops, so does the output power until it hits the point that the cd player will no longer turn on. So no, it will not last 2 hours at all.

It really depends on what battery you have.
But yeah, lots of things to be taken into consideration.
But you definitely 100% need a deep cycle battery if you plan on depleting, then charging.

Ok,thanks.I am little slow with this.I know how to get loud but not how to stay loud.I need the longest I can get.If it is 2 or 3 yellow tops I'll try that.