Powering a sound system by marine/car battery?

golgotha-a-go-go · Post by **golgotha-a-go-go** » Thu Jul 26, 2007 8:48 am

Advice needed on powering a mobile dj's sound system by using marine/car battery. Will be hauling it around on a little bike trailer and setting up impromptu on outer playa. A couple of portable cd players + 2 small speakers. What's the practicality? Limits? Capacity of battery? Appropriate equipment, other power options, etc? Any existing thread on this?

Golgotha-a-go-go

capjbadger · Post by **capjbadger** » Thu Jul 26, 2007 9:11 am

There are many threads here on batteries and such. Long stony short, don't use a car battery. You'll kill it. Look for deep cycle batteries. Golfcart batteries are an option.

Badger

phil · Post by **phil** » Thu Jul 26, 2007 11:03 am

Batteries are rated at amp-hours. I've got 7.5 Amp-hour batteries. They'll power 7.5 amps of gear for one hour or 1 amp of gear for 7.5 hours or 3.8 amps for 2 hours - you get the picture.

While DC power is rated in amps, AC power is rated in watts (I assume your gear is 110VAC), so you need to convert watts to amps to see how many amps of battery you need.

Here's the formula (and be prepared for disappointment):

Amps = Watts x Volts

Figure out how many watts your sound system requires. I've got a Philips desktop micro hi-fi on my desk, for example. It requires 110VAC, 60Hz, 30W. My battery supplies 12VDC. So 30W x 12V is 360 amps. I need a 360 Amp-hour battery to play the radio for an hour.

I've got a 100 Amp-hour battery, so that will play my stereo 100 / 360 = about 17 minutes.

I suspect your system runs on 110VAC, so you'll need to figure in an inverter to change 12VDC to 110VAC; the inverer uses a small amount of power, so guess maybe 15% of your battery's life will go for that. 15% of 17 minutes down the drain gets to be significant. :->

If 17 minutes isn't enough, you'll need to buy more amperage by getting a bigger more powerful battery or more smaller batteries, or you'll need to recharge the battery(ies) you have.

NOTE: the watts your system requires is not the rated output in watts; it's the amount of current the system requires to operate. My desktop radio claims to have output power of 20W into 2 speakers for a total of 40W output. However, it draws 30W when playing, and that's the wattage we're concerned with. Look on the bottom or back of your system and you'll find a label with the voltage, herz, and wattage the unit expects to see to play.

Maybe unjon harley will jump in. He rides a bike around playing music, and he's quite the babe magnet on the playa.

capjbadger · Post by **capjbadger** » Thu Jul 26, 2007 11:55 am

Whoooa... WHAT?? nono..
Watts = Amps x Volts
Amps = Watts / Volts

Your 30W radio toplay for an hour would need 2.5Amphour battery.

Badger

bigbluedoggy · Post by **bigbluedoggy** » Thu Jul 26, 2007 12:07 pm

uh... yeah... what badger said!!!

phil · Post by **phil** » Thu Jul 26, 2007 1:46 pm

Crap! Sorry. Dang. Many apologies.

Hoolie · Post by **Hoolie** » Thu Jul 26, 2007 8:37 pm

capjbadger wrote:There are many threads here on batteries and such. Long stony short, don't use a car battery. You'll kill it. Look for deep cycle batteries. Golfcart batteries are an option.

Badger

What kills the car battery?

phil · Post by **phil** » Thu Jul 26, 2007 8:51 pm

Hoolie wrote:What kills the car battery?

See
http://www.cieux.com/bm/batteryWreck.html

dragonfly Jafe · Post by **dragonfly Jafe** » Thu Jul 26, 2007 8:57 pm

Hoolie wrote:
capjbadger wrote:There are many threads here on batteries and such. Long stony short, don't use a car battery. You'll kill it. Look for deep cycle batteries. Golfcart batteries are an option.

Badger
What kills the car battery?

there are two types of batteries; quick discharge (car starter battery) and deep discharge (deep cycle battery).

A car starter battery has many thin plates. The greater surface area allows a large amount of electricity to be dumped quickly, but prolonged drainage will pitt the thin plates, and they will never fill back in. Also, there is less distance between the bottom of the plates and the bottom of the battery case, so "sludge" from the chemical reaction can "short out" the plates quicker.

A deep cycle battery has fewer plates, but they are thicker, so deep draws will not pit the plates, and during recharge all is replaced. There is also greater distance between the bottom of the plates and the bottom of the battery case, allowing a greater amount of "sludge" to build up before things go bad.

This is my version, others may have a more technically correct description.

Hoolie · Post by **Hoolie** » Thu Jul 26, 2007 9:08 pm

Ok, I've got it now. How would starting/deep cycle be classified? The reason I ask is I plan on using this battery to power a small sound system, but I don't see anything in the description specifying which type it is. (Since one specified use was "e-bike", I assumed this would be the kind of battery that could be fully discharged).

Angel Ben · Post by **Angel Ben** » Thu Jul 26, 2007 10:23 pm

Yes, that battery will work fine. Sealed Lead Acid or Gel Cell is the type of battery you want. These are usually used in from scooters, golf carts, and UPSs. That's a pretty small battery though. I'm actually using 4 similar batteries linked in 2 sets of series for a mobile sound system of my own (my average draw is only about 1 amp, though). That way I'll always have 1 pair running and 1 pair charging on a solar panel back at camp.

spectabillis · Post by **spectabillis** » Fri Jul 27, 2007 1:34 am

even though you ruin a car battery, doesnt it keep working for at last one week? there's a lot of cheap used batts, new deep cycle can cost a couple of hundred when you're not going to use it that much after the event.

of course thats not very green, i guess.

sal_monella · Post by **sal_monella** » Fri Jul 27, 2007 4:20 am

Have you thought about one of these? Powerpack 600HD
http://www.xantrex.com/web/id/182/p/1/pt/29/product.asp

It will power a
40W appliance for 7 hours
14W for 15 hours
5W for 56 hours

You can pick one up on ebay for under $100

I was thinking about using solar panels to power something and after looking at the price and trial and error to get it to work, just decided to go a lower tech route.

spectabillis · Post by **spectabillis** » Fri Jul 27, 2007 6:09 am

not a bad idea, but i wish they would list the weight and dimentions.

Hoolie · Post by **Hoolie** » Fri Jul 27, 2007 8:33 am

Angel Ben wrote:Yes, that battery will work fine. Sealed Lead Acid or Gel Cell is the type of battery you want. These are usually used in from scooters, golf carts, and UPSs. That's a pretty small battery though. I'm actually using 4 similar batteries linked in 2 sets of series for a mobile sound system of my own (my average draw is only about 1 amp, though). That way I'll always have 1 pair running and 1 pair charging on a solar panel back at camp.

I'm making a small sound system for my playa bike. So, I didn't want anything too heavy. Even though this battery is relatively small, it still weighs 5.5 pounds. Plus I have to add the weight of the speakers, cabinets, amp, ipod, cables, etc. I want to be able to cruise freely without being weighed down too much, so I'm striking a balance between sound quality, weight, and battery life. I won't be blowing anyone away with booming bass with this system, but it still sounds decent. Once I get it all together, I'm going to test how long it can go on one charge. Depending on the results, I may get another one of these batteries. Also, as a final backup, my little amp can actually run on 8 AA batteries.

Angel Ben · Post by **Angel Ben** » Fri Jul 27, 2007 8:41 am

Ah! So you've got the T-Amp as well, then? I absolutely love that little guy; what sort of speakers are you using?

capjbadger · Post by **capjbadger** » Fri Jul 27, 2007 8:56 am

Hoolie wrote:Ok, I've got it now. How would starting/deep cycle be classified? The reason I ask is I plan on using this battery to power a small sound system, but I don't see anything in the description specifying which type it is. (Since one specified use was "e-bike", I assumed this would be the kind of battery that could be fully discharged).

If the battery doesn't straight out say auto, marie or deep cycle, there are hints you can look for. If it talks about AH (AmpHours) in the description, it most likely is deep cycle. If it talks about "cranking amps", then it's a starter/car battery.
Marine batteries are somewhere inbetween.

Badger

Hoolie · Post by **Hoolie** » Fri Jul 27, 2007 9:27 am

Angel Ben wrote:Ah! So you've got the T-Amp as well, then? I absolutely love that little guy; what sort of speakers are you using?

Yeah, it's the T-Amp. I am using some 4" speakers from an old Pioneer bookshelf stereo system. I've made a couple boxes to place them in along with the amp and battery. They will attach to my rear rack.

Hoolie · Post by **Hoolie** » Fri Jul 27, 2007 9:28 am

capjbadger wrote:
Hoolie wrote:Ok, I've got it now. How would starting/deep cycle be classified? The reason I ask is I plan on using this battery to power a small sound system, but I don't see anything in the description specifying which type it is. (Since one specified use was "e-bike", I assumed this would be the kind of battery that could be fully discharged).
If the battery doesn't straight out say auto, marie or deep cycle, there are hints you can look for. If it talks about AH (AmpHours) in the description, it most likely is deep cycle. If it talks about "cranking amps", then it's a starter/car battery.
Marine batteries are somewhere inbetween.

Badger

Cool, thank for the info, Badger.

phil · Post by **phil** » Fri Jul 27, 2007 10:12 am

spectabillis wrote:not a bad idea, but i wish they would list the weight and dimentions.

Amazon is your friend:
http://www.amazon.com/Xantrex-852-2000- ... 388&sr=8-1

Executive summary: Measures 14 x 22 x 9.2 inches; weighs 29 pounds/