Bike-portable sound systems - battery questions

[marcelmouse]

I'm currently toying around with the idea of building a car stereo into a bike trailer. I've read a few pages about the topic, but I'm having a hard time designing an optimal system.

Most of the stuff I've read comes from one of two communities. There are British festival-attendees whose pages show pictures of exactly what I want, but are pretty scanty when it comes to technical details. The other category are RV-people, who offer all kinds of details but assume different end uses. So, based on the posts about this issue I've already found by searching the archives, I thought that I'd throw my quesion out to the e-playa community.

1) It seems easy enough to power a car stereo with a few batteries. Most of the sources I've checked seem to indicate that a pair of 6-volt golf cart batteries are the sweet spot in price/performance ratio. This is great if everything I need to power is 12volt DC, and I could do it that way (barring the massive pocketful of AA batteries I'd need for the MP3 player). Any thoughts?

2) However, what I'd REALLY like to do is power not only a bass-heavy soundsystem, but also my laptop, a few samplers, and a mixer. What's the best way to accomplish this? Should I try some sort of battery-to-120V AC power (I bet this is spendy)? Or should each piece of gear get its own bettery? F"rinstance, I think that the Boomerang phrase sampler wants 14V at something less than an amp (guessing), while the Handsonic requires 12V 1A, and the synth requires 8V and half and amp. Is it easier to power each of these things separately, or should I just study up and try to build a single system myself?

I have many more questions, but this sounds like a good stopping point.

[willx001]

You need to get "deep charge" batteries, a batteries charger and an ac converter.

You can find Free batteries at your local community Toxic Waste Disposal. The same place you take your paint cans so they don't end up in the landfill. You should be able to call and find out if they take batteries. If they do you can probably talk them out of a few of the batteries other people have droped off. People take in Deep Charge Marine Batteries. These batteries usually have the ability to take a charge. (cheaper and better for the environment) I've got a number of them and they are all good for about 400 amps each or more. Amps X Volts = Watts. So if you have a 100 amp continuous power amplifier, you can run it for 4 hours. Or if you want to run a 40 watt light you can run it for 120 hours.

If you wire your batteries in parallel you increase the amps,

Series you increase the volts,

If you get a battery that dose'nt work. Please return it to the Toxic Waste Disposal.

wi

[Captain Goddammit]

To get 120vac from your 12v batteries you need an "inverter". You don't need an expensive one because your power requirements are pretty low.
Check auto parts stores, Costco, Target... I just got an 800 watt continuous, 1600 peak unit from Shucks auto supply in Seattle for $50.
The 8 to 14 volt stuff will probably be happy at 12.
Your only big power draw will be the amp. It will be simpler, lighter, smaller, and more efficient to use a 12v car-stereo amp directly off the battery. The amp will be a battery-killer unless you get pretty high capacity ones, and I assume you have a way of recharging your batteries at your camp. (?)

If you're gonna have big 12v batteries, why use handfuls of AA batteries for the mp3 player? Most have a power input jack and adapters are available to reduce 12v to any lower voltage in 1.5v increments to match the level of any combination of AAs. Use one of these.
willx001 is talking about "deep cycle" batteries. They're designed to produce small amounts of current for a long time, as opposed to car "starting" batteries that are designed to discharge a lot of current for short periods of time. I'm less optimistic than he is about using batteries that someone else had a reason to throw away...

[Bob]

You don't say why you want to do this.

I've seen (ambient) "sound systems" on the playa the size of a soup can, but it sounds more like you want to put a rave on a bicycle.

[marcelmouse]

Thanks for your responses... this stuff is really helpful.

You don't say why you want to do this.

I've seen (ambient) "sound systems" on the playa the size of a soup can, but it sounds more like you want to put a rave on a bicycle.

No, I actually want anti-rave on a bicycle. One of the things that is most frustrating about the playa is the endless thump of house music.

(I don't mean to single out enthusiasts of house music. I do appreciate their music in moderation. However, let me just generalize a bit and say that I NEED some way to carry music with me that's a) not constantly four on the floor, and b) periodically features real acoustic instruments that haven't been dreadfully overproduced. Or, I could just make a ten-hour MP3 mix and listen to it on headphones the whole time, but this doesn't seem very participatory,)

I just want to have a 15' radius island of experimentalism out on the playa that consistently represents the tastes of myself & my friends. Aforementioned friends want to camp in the walk-in area, so a permanent installation is out. It doesn't need to be hugely loud, but if we're performing improvised music out on the playa, it would nice to be able to hear one another when an art car with a techno soundtrack drives by.

There are some kinds of things that I would like to do that can't be handled by soupcan/boombox/various consumer-grade subless systems. So, I'd like a bit more wattage than the average soup can - for example, we use phrase samplers to loop things like acoustic bass & percussion on the fly. Show me a soup can with decent bass response & I'll weep with joy.

[Tiahaar]

Yes do think through how you are going to recharge your deep cycle battery powered, bike pulled music-machine. That may turn out to be the most costly bit of all. One of those famous Honda eu1000/2000 generators could do it nicely (with a high output battery charger in 2-5 hours or so) but unless you already have one they are $$ (and I hesitate to suggest...but done cleverly you could build a little quiet-box and just take the generator with you and forget about the battery part). If you're in walk-in you won't have a car to charge it off of (and would take forever anyway) and a solar array big enough for a one-day turnaround from 10% to 100% charged would be huge (something putting out 10 amps of charging would be about 4'x6' for 150 watts if the sun is bright...ballparking a lot of this, sorry!) and also $$, like $3-4 a watt. Or bring a battery for every day of the week and charge them up at home first, heheh. Just kidding (hmm, are generators allowed in walk-in?)

[Tancorix]

I just bought a Honda EU2000i yesterday, and it weighs in at 46 1/2 lbs. And it's super quiet especially when you turn on the eco-throttle. Compared to the normal cacophony of BRC and how much load you'll use a shielding box might not be required, they really are that quiet. I'd hate to pull around extra batteries and shielding on a bike as the deep cell batteries are not light.

If you buy a genny like the EU2000i, use Google's Froogle to get an idea of the pricing. Also if you buy the Honda....check inside and see if they put the 2004 upgrade sticker in there. It seems they've improved some things to make a good genny even better.

[Captain Goddammit]

Generators aren't welcome in walk-in suffering... er, camping.
And I can't believe you'd put in a disparaging remark about our fine man-of-the-year, doesn't speak for Burning Man but acts like he does, nice guy extrordinaire... Badger....

[marcelmouse]

I was going to deal with how-to-charge-it after I had figured out whether or not what I wanted was possible. My half-baked plan was to make charging arrangements with friends in larger camps who are actually bringing serious generators.

In fact, if that Honda e1000 generator is powerful enough, building some kind of sound-supression box for it and putting it in the bottom of the trailer might actually be the best solution. Depends on how easy it is to rent, though; the retail on one of those would just about eat up the funds devoted to this project in general.

How quiet is quiet, anyways? Perhaps someone who has used one of these can tell me. I've never done the math for a problem like this: "Given that this generator produces X dBs at full throttle, design a sound-supression box such that the generator is basically inaudible when placed under a soundsystem kicking out Y watts."

(I think a simple "Yeah, it's doable" or "not a chance" will do.)

And I can't believe you'd put in a disparaging remark about our fine man-of-the-year, doesn't speak for Burning Man but acts like he does, nice guy extrordinaire... Badger....

Umm... who? what? Did I make a disparaging remark? Is my stance against four-on-the-floor offensive? To this Badger character whom I've never heard of, or someone else?

[marcelmouse]

Sorry, I should have specified, given that you spoke specifically of the 2000 - is the 1000 similarly quiet so as to not require a box?

[Tancorix]

Marcel, CG was talking about me concerning the Badger comments. As for the generators, the Honda specs can be found here:
http://www.hondapowerequipment.com/gensup.asp

I just finished struggling with building shielding boxes and while it's possible to silence the things, it's very difficult to get rid of the heat and get enough airflow in for the engine to run (and the 4000 ft of altitude and the corresponding power loss makes that even more critical). If you put even an EU1000i in an enclosed space without the right ventilation you'll have a $650 piece of metal covered in melted red plastic. It could be pretty but that's not the kind of art you want to make.

You should be able to run a 1000 or 2000 without any shields, boxes, or fancy stuff because they are pretty damn quiet (Honda's engineers earned their pay on these designs!)...and your music should easily drown out the remaining sound. I can say all this but the best thing is to find someone that has one and have them fire it up. (Run it with the eco-throttle on and off and even without the eco-throttle it's still much quieter than anything else out there.) Then you'll understand and the answers to your problems should fall into place.

[Captain Goddammit]

Will second Tancorix, done the quieting-box experiments too, airflow is a big problem. You will contain too much heat.
And the little Hondas are quiet enough already, nothing at all like those lawnmower-engine things.

[Tiahaar]

One way to do the "quiet box" thing is to get 3/4" plywood and make an open-backed box several inches wider/deeper and maybe 1 1/2 times as tall as the genset, line it with heat-sound-shield insulation (optional), fasten/strap the generator down with something underneath it to isolate vibrations from the box, and then mount the whole thing at the back of the trailer with the open side of the box pointing backwards too. Its really more just directing what little sound the Honda makes away from you and the completely open back keeps things running cool. Just had a thought...a big trashed speaker/amp cabinet would make a great box to start with.