Powering Car Audio Indoors

Cpyder

Hey guys,

I'm interested in using some car audio in a home audio application. I know there are drawbacks and some people would caution against doing this, but I'm going to try it out anyway.

The main problem is getting 12V power to the system. After researching this, I think I am going to try to use a car battery and a 120V battery charger. While in use, the system will run only off the battery and when the system is switched off, the charger will recharge the battery. My question has to do with the battery requirements. I'm somewhat familiar with battery choices as far as different types and capacities.

From what I've read, a sealed AGM type battery is a good choice in this situation.

As far as capacity goes, I understand that a 100Ah battery can supply 100A for one hour, 50A for 2 hours, 25A for 4 hours, etc. But I'm not sure how to calculate the size I need. At loud volumes, the system may draw 350 watts at about 4 ohms. But what about at normal listening levels?

Wattage = Voltage x Amperage

Let's say normal listening levels uses 50W. So at 12V, the current draw would be 50/12=4.2A. This would seem to imply that a 100Ah battery could sustain this output for about 24 hours which would be a very long listening session. Perhaps a 50Ah battery would be fine then.

Am I calculating this correctly? Any help would be hot. Thanks!

Bonus question: Is it possible that during sharp bass hits, the battery would not be able to react fast enough and it would sound muffled at higher volumes? Is this even a possible problem?

nguyendot

Probably easier to just get a high powered 12v power supply. Using high powered batteries like that indoors with improper ventilation is generally a no-no. Also, it'll sound like crap.

decal

I used a car system in my bedroom, when I was thirteen years old !!!!!

steveinaz

Pyle audio sells a 12v power supply....

Cpyder

nguyendot wrote: »

Probably easier to just get a high powered 12v power supply. Using high powered batteries like that indoors with improper ventilation is generally a no-no. Also, it'll sound like crap.

What exactly about it would make it sounds like crap?

Cpyder

Correct me if I'm wrong, but shouldn't the system be very low noise since there are no other components connected to the power supply? With AC, every device in your house can theoretically cause interference, right?

Joe08867

That would be the case if all things were equal but car audio is not on par with Home audio. The limitations of space in the car audio realm make the components smaller not better. There is more noise introduced by the miniscule electronics in you car stereo than almost any home stereo.

Cpyder

Lasareath wrote: »

I've used an old laptop power supply:


http://www.youtube.com/watch?v=42PqbiSfy9k&feature=youtube_gdata_player

Very nice! How does it sound?

jbooker82

If your going to use a battery you sould use a Deep cycle battery. They are designed to be charged and discharged. They do not produce huge cca ratings but they can deliver a steady power suply longer than a conventional car battery.

Something like an Optima Blue Top battery.

CoolJazz

A regular car style trickle charger will, over time, cook a battery if left hooked up. :evil:

If you go this route you have to find a "dual-rate" charger. Basically after the needed trickle charge cycle, they drop down to a very small maintenance mode. Without this very low rate charge, you run the cells hot and will cook a battery in a matter of a few months. The fishing guys are familiar with these type chargers and that's good place to look.

CJ

nguyendot

Cpyder wrote: »

What exactly about it would make it sounds like crap?

Because car audio is no where on par with home audio. Car speakers are designed to be hardy, not sensitive. Also, judging your whole setup based solely on the power supply because it's not hooked up to mains is not quite accurate. Remember you have to look at the quality of the rest of the electronics, and drivers.

skrol

As long as you run the battery down a little once in a while it should not cook.

If you use a battery to power your system, don't have a battery charger running to maintain the battery. Battery chargers are not very refined power supplies and will produce noise. The pure DC off the battery will prove much quieter. Recharge the battery after you are using the system.

As mentioned above, you may be better off with a decent 12V power supplies available that provide very good filtering.

Stan

Cpyder

Would it just be better to use the Marantz SR5003 receiver I have for this project? Would it be possible to run a pair of components (Polk Audio SR6500) and two small subs (JL Audio 6w3v3) off this receiver? I'd probably need a crossover for the subs...?

Cpyder

Never mind. It probably won't handle the resistance of the speakers. 4 ohms is a tad too low.

inspiredsports

In the mid 70's I bought a nice 110AC to 12VDC converter from Radio Shack.

I had it wired to an automative system that someone had given me consisting of an AM/FM/CDP driving two 6X9 3-ways in boxes.

The converter was quiet (and my only investment in the otherwise free system). I used it in my shop for many years before retiring an "upstairs" rig to the shop.

Syndil

nguyendot wrote: »

Probably easier to just get a high powered 12v power supply. Using high powered batteries like that indoors with improper ventilation is generally a no-no. Also, it'll sound like crap.

True, true, and true.

Charging a 12V battery can sometimes result in the release of hydrogen sulfide gas if the battery is damaged. Outdoors, not a big deal. Indoors, it can kill you.

Cpyder

Syndil wrote: »

True, true, and true.

Charging a 12V battery can sometimes result in the release of hydrogen sulfide gas if the battery is damaged. Outdoors, not a big deal. Indoors, it can kill you.

Does this include even the sealed type batteries?

Syndil

If they are damaged, yes. And if you are constantly charging a 12V battery that is not being constantly discharged, you will likely boil the electrolyte, potentially causing the battery case to swell and crack. It's really just not a good idea and is totally unnecessary to boot. I'm not sure what advantage you think you will gain by using a car battery. If you really want to run car audio indoors, then depending on how much amperage you'll require, you may be able to find a 12V DC power supply for less than the price of a new battery. You don't think that stores that demo car audio gear are running them off of car batteries, do you?

skrol

The only advantages to a battery that I see are the current capability and pure DC. For bench testing I use a 12V regulated supply by Emco (I believe) that is 7 amps constant and 9 amp peak. The filtering is actually pretty good and it was cheap ~ $50.
Stan

tonyb

Color me clueless, but why on earth would anyone want to put car audio in the home ?

Must be a try out for some new reality tv show. Enough has been said already about the dangers of using a car battery in the house so let me just say be careful or you'll be getting coloring books for your birthday in the future.

Joe08867

tonyb wrote: »

Color me clueless, but why on earth would anyone want to put car audio in the home ?

Must be a try out for some new reality tv show. Enough has been said already about the dangers of using a car battery in the house so let me just say be careful or you'll be getting coloring books for your birthday in the future.

I know someone that did a marine car stereo in the bathroom with marine speakers in the ceiling, but besides that I can see no real reason.

Cpyder

Syndil wrote: »

...And if you are constantly charging a 12V battery that is not being constantly discharged, you will likely boil the electrolyte, potentially causing the battery case to swell and crack...

If this were to be done, I believe Skrol gave the correct answer for how to charge and discharge the battery:

skrol wrote: »

As long as you run the battery down a little once in a while it should not cook.

If you use a battery to power your system, don't have a battery charger running to maintain the battery. Battery chargers are not very refined power supplies and will produce noise. The pure DC off the battery will prove much quieter. Recharge the battery after you are using the system...

CoolJazz

Cpyder wrote: »

If this were to be done, I believe Skrol gave the correct answer for how to charge and discharge the battery:

Nope. This isn't a battery "memory" issue. This is a case of cooking the battery by a continous charge that will cause the cells to run hot all the time and create a total battery life of only a few months. Discharging it once in a while will not effect this.

Buying the proper type of charger is the correct answer. A typical car charger will cook a battery when left long term on the low cycle.

CJ

SDA1C

Do NOT charge a battery indoors (i.e. in a house or shed). Recipe for disaster. Hope you don't smoke lol or have ANY spark or flame sources.

I have one of these for my radio work and cb base. It's almost indestructible and can be had for 200 plus shipping. Great deal for a little peace of mind.

http://www.pacetronics.com/prodpage.cfm?Cat_Selected=37&Subcat_Selected=116&Group_Selected=278&product_Selected=728


1C

zingo

Those power supplies are very good and thus, not cheap. If you really want to go hog-wild on battery powered audio, LiFePO4 batteries are the preferred choice as they have great characteristics. However, with the money spent on either a good power supply or batteries, why not just spend that money on home audio equipment?

skrol

CoolJazz wrote: »

Nope. This isn't a battery "memory" issue. This is a case of cooking the battery by a continous charge that will cause the cells to run hot all the time and create a total battery life of only a few months. Discharging it once in a while will not effect this.

Buying the proper type of charger is the correct answer. A typical car charger will cook a battery when left long term on the low cycle.
CJ

I am not referring to a memory issue as would be the case with NiCd batteries. You are correct in that if you continue to charge a battery that is already at a full State Of Charge (SOC), even at low current rates, it will overcharge and get warm or even hot and produce excess hydrogen. Overcharge is the main killer of batteries. I am only suggesting to discharge once in a while to prevent overcharge. A deep discharge is still good in that it helps to prevent sulphate build up on the plates. That is why your car battery last so long. It experiences discharge and charge cycles on a regular basis.

A wet lead acid battery can be charge safely indoors with the proper charger. For example, I have a backup on my basement sump pump that uses a deep cycle wet lead acid battery and has a small float charger. I would not consider a regular car battery charger as proper for indoor use as it is capable of significant current to cause a battery to boil and rupture if it fails to detect that the battery is at full SOC. A float charge should be OK.
Stan

Cpyder

CoolJazz wrote: »

Nope. This isn't a battery "memory" issue. This is a case of cooking the battery by a continous charge that will cause the cells to run hot all the time and create a total battery life of only a few months. Discharging it once in a while will not effect this.

Buying the proper type of charger is the correct answer. A typical car charger will cook a battery when left long term on the low cycle.

CJ

I believe the charger one would use would be a smart charger. They fast-charge the battery to around 80-90% and then trickle-charge the rest and then maintain the battery when they are done. Does anyone know if you can leave these plugged in indefinitely?

skrol

I would not recommend leaving it connected and charging, even trickle charging, indefinitely. The chargers use a voltage slope detection (dv/dt) to determine that it is fully charged. Hopefully it also has an absolute voltage cut-off and a timer as backup protection. The slope detection is looking for a slope change. If the charger happens to go back to full charge mode, could be caused by a power line fluctuation, and the battery is at full SOC, there may not be enough of a slope change to trigger charge cut-off and step-to-trickle. In this case the battery will over charge until one of the other protections, if it has them, activates. By the way, not all 12V car battery chargers are "Smart Chargers" and not all have back-up protection. I just threw one away a couple months ago because it did not have any such protection.

There are chargers available to constantly maintain a battery. Look at RV stores since they are usually for campers and boats.

I understand the desire to use a car audio system indoors. When in college, my car stereo was much better than my home stereo. I have been curious about this lately since I am pondering going with a separate amp but having trouble justifying laying out the money (4 young kids and a wife to feed). Meanwhile, I have a few really nice Alpine amps in my basement doing nothing. I also have a spare car battery, a trickle charger and a nice size solar panel just waiting for a project...hmmmm... I probably should sell the Alpines to help fund a decent Adcom or Carver but where is the fun in that?
Stan

gdb

Here's an idea.......run a mini gas generator inside, one that outputs 12V DC.

20hz

Dont be sure on that ..
I was looking at a small home amp I found a cambridge music (not the cambridge audio) you see in malls but cambridge music is a british that makes some clean sounding stuff , it sounded good I asked them if I could A/B test it with another amp they didnt mind at all , I went and got my tester amp its a hafler 100+100watt driven with a computer grade power suppley ( $20 used )
The salesman laughted as I brought my setup in mounted on a board but them as did I agreed that hafler sounded better then the cambridge amp , it wasant volume based it was warmpth of sound and this was a high end shop .
PS : mcintosh built car stereo stuff and I heard it sounds great .

nguyendot wrote: »

Probably easier to just get a high powered 12v power supply. Using high powered batteries like that indoors with improper ventilation is generally a no-no. Also, it'll sound like crap.

SDA1C

Agreed 20hz! I would think at times the 12v would be cleaner....as long as you aren't sniffing sulfuric dioxide in the process lol