Deep Cycle Battery Life?

[Millstonemike]

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Yeah, probably gonna do the China Fright genny... FWIW, we're usually at the "top right" of the attached photo...

You might have to go with the generator. A 12 V battery and 8 ohm speakers cannot put out more than ~8 Wrms regardless of the chip amp. That's physics as max rms power is:

Prms = (V_ps-1)² / (2 * SPK_r). That is W rms = (Power Supply voltage - 1) squared then divided by (2 times speaker impedance).

With two smaller 12 V batteries in series (i.e. 24 V) you can get 33 W rms per channel.

The system pictured is getting 66 W rms into the ".1" 4 ohm sub. You can see the two sealed lead acid batteries: 12 V, 18 aH. This plays for two days at 10 hours per day as there's no losses up converting a single 12 V battery and the 2.1 channel amp module is Class D (TI's TPA3116 amp chip). The batteries are roughly $45 each. And you'll need a SLA charger (~$35) to keep them topped off. You could then use many of the class D amp modules on PE's site. With the proper SLA charger, my first 12 V 18 aH battery lasted 8 years doing beach duty both days every weekend..

On another note, you may lack some bass since you outside w/o walls or floor to reinforce it. That's due to the "Baffle Step" phenomenon. The system below corrects for that in it's XOs.

(The system below is for sale including SLA batteries and two SLA chargers (and a second 24 V Li-ION battery and charger). Custom designed for lightweight, high volume beach parties, long battery life, and ease of transport with it's rugged case. In NJ).

[Shibli8]

I don't know much about battery life lasting. But you can search on google for more info about batter life.

[TheBogie]

Well, the web site for the general event is www.machinegunshoot.com - you may have seen footage of it on ABC over the weekend when some genius at ABC tried to pass it off as "the invasion of Syria." Not sure about the model numbers, but they're 15" woofs with horns for the tweets. I'm not going to bring any additional subs. Probably mostly just playing some old country/grass and mellow rock for our general area... Some folks about 300 yards off last weekend were jamming on some Hendrix, for what that's worth. Pretty much just figuring on getting one of the chip amp setups that PE has, rather than take a larger receiver.

These are currently my living room speakers - I had to get rid of the maggies when I moved in with Jen, because I knew her kids would destroy them - as it was, they trashed some perfectly good Infinities... I've got my two sealed Quatros left, and two more in the big box of whoopass in storage...

Yeah, probably gonna do the China Fright genny... FWIW, we're usually at the "top right" of the attached photo...

[Millstonemike]

Here's why I asked about your model speakers and the amp your considering ...

Battery power is convenient if it will do the job. The first requirement is playing time. The second is the battery/amp/speaker system design. That will determine the volume of your output.

I presume the DJ like "Gig" speakers are 8 ohms. That works against you on battery power as 8 ohm drivers require a higher voltage than 4 ohm drivers given the same power out. That's why all car speakers are 4 ohms - more power from the nominal 12 V auto system. In their favor, "Gig" speakers tend to be efficient.

I designed a 2.1 beach boombox. I get 109 dB with an f3 of 42 hz.. Five hundred people rise when I play the national anthem in the morning. And I'll play all day, some 8 to 10 hours. All on a 24 V, 18 ah lithium pack with power to spare.

Your camping trip may become a annual ritual. So you want to do this right. You have to weigh the different systems. Transporting a generator, fuel, and power cable (you'll want the generator way away from you) versus a battery (w/charger at home).

Speaker model and potential amp? How many days out camping? How big is the group?

[Kornbread]

Camping trip? 15" Speakers? Outdoor party?

Marine batteries come in various sizes and price ranges from a cheap ~$100 up to ~$1000 for a lithium and not sure of which little amp you are referring to, but since you are not really 'camping' but having an outdoor party (not worried about listening to nature) get one of those small HF generators. There not that loud and will come in handy at the most inopportune of times.

YMMV

[Millstonemike]

More info on the speakers and the amp would shed more light on the question.

[TheBogie]

So, I'm back to doing some of the things that I love, and one of them was organizing a big camping trip to Knob Creek every year. Next spring, I'm planning on stuffing a pair of 15" Yamaha gig speakers in the back of the van, along with a deep cycle and one of the little amps that PE sells.

So, how long do I figure on being able to run the thing on your basic marine battery? Or should I just figure on getting one of the $100 generators from Harbor Freight?