A long time ago I relocated my battery to the trunk in my civic. I did it the cheap & lazy way (used the 4awg cable that I was using for my amp).
Anyways, I'm finally going to redo it properly and want to upgrade my battery setup while I'm at it.
My battery box is 10"W x 14"L x 9"H and can fit 2 stock batteries and still has quite a bit of room. I have 2 good working stock batteries, but setting up 2 batteries and an isolator all in the same box seems kind of pointless to me.

So I'm thinking I might get better results from 1 big battery than 2 little ones. It's simpler and simpler is almost always better. The box will fit any size battery except 95R/4D/6D/8D/GC2/GC2H. So I was thinking about getting a nice big deep cycle marine battery.
Does a bigger battery need more or less power/time to recharge than 2 smaller ones?

Any help would be appreciated

 

Why do you think you need 2 batteries to begin with? Do you play your system for a long time with the car off? Best bet is one good battery. Kinetik, Optima yellow top, ETC. and a high output alternator.

 

OPTIMA!

 

charging time depends on the Ah capacity of the battery/ies. Add them up and whichever one is greater will take longer to charge. Either way 2 batteries will be way more work than you want to do, stick with the optima single battery.

 

It depends on what your system goals are. If you desire a solid 14.4 volts at idle and being able to keep that throughout most of your daily driving with a decent sound system, two batteries isn't a bad idea. But then again, it depends on what all you plan on using. If you don't plan on having any system at all, don't do a second battery - just stick with a solid factory replacement. I had 2 batteries in my teggy but I also had 3800 watt capacity (XX Colossus and a 4 channel Sundown) that ran more zero gauge in the engine bay and cabin than you've probably seen in a daily driven vehicle. Oddly enough the car was built for SQ, not SPL. But that's another story.

Anyway, the question is - what do you plan on doing with the car? Are you planning on a system or not? If so, how big of a system?

If you don't plan on having a serious sound system, don't bother with dual batteries at all. It's just adding weight at that point for no considerable gain for driving alone.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Electrodynamic &raquo;</TD></TR><TR><TD CLASS="quote">It depends on what your system goals are. If you desire a solid 14.4 volts at idle and being able to keep that throughout most of your daily driving with a decent sound system, two batteries isn't a bad idea. </TD></TR></TABLE>

Wait, wat? If I put another battery in my Accord, my alternator will magically put out 14.4 volts? Maybe I should put 3 in. Then I'll hit 16 volts...



As stated above, another battery will do nothing besides allow him to extend his play time with the engine off.

 

With two batteries, your system capacity to maintain 14.4 volts goes through the roof. Most cars sit close to 14.4 at dead idle, but then go down considerably once a load is put on them. Install a second battery and your reserve is significantly higher. A HO alt helps a ton (I had a 160 amp alt in the teggy), but a second battery will improve your chances of maintaining 14.4 better than a single battery, single alt system.

Or you can go on believing that a second battery is good for nothing other than operating your system while the car is off, but that's being a little ignorant. Take a look at ANY SPL sanctioning body and notice the different classes based off of multiple batteries and their locations. There are not only different classes for multiple batteries, but also for extra batteries in non-stock locations. Then there are classes for car-on and car-off. If you want to go even further, look at the extreme (literally) classes in IDBL, MECA, IASCA, etc, and you'll notice that they are all running MULTIPLE batteries and multiple alts...not just a bunch of alts and a single battery. You have to have power (12v to 16v+) to make power in the car audio realm.

 

And then theres the topic of upgrading a single battery to a serious competition-grade battery vs. using dual stock batteries, etc. ...let alone just upgrading your stock battery to something like a normal yellow top Optima (there are two different kinds of yellow top's).

 

Well (B18C_EJ8) I was going to respond to the above ^^^ and I will, as soon as I stop laughing. 94

 

I still can't believe what I'm reading here.

 

Here is some good reading.

Charging System Basics:
The electrical system in an automobile is said to be a 12 volt system, but this is slightly misleading. The charging system in most cars will generally produce a voltage between 13.5 and 14.4 volts while the engine is running. It has to generate more voltage than the battery's rated voltage to overcome the internal resistance of the battery. This may seem strange, but the current needed to recharge the battery would not flow at all if the charging system's output voltage was the same as the battery voltage. A greater difference of potential (voltage) between the battery's voltage and the alternator's output voltage will provide a faster charging rate.

As long as the engine is running, all of the power for the accessories is delivered by the alternator. The battery is actually a load on the charging system. The only time that the battery would supply power with the engine running is when the current capacity of the alternator is exceeded or when engine is at a very low idle.

Upgrading Your Charging System

Alternators:
As we said on the charging system basics page, the alternator supplies all of the power to all of the electrical accessories (amplifiers, lights, power windows, power seats...) as long as the engine is running. Upgrading the alternator is generally the most cost effective way to add more performance to your system. In the next few paragraphs I'll attempt to explain why other remedies may not solve your problem and may even make it worse.

Many people want to know when they should replace their alternator. The short answer is... when it fails. If you just want the battery to remain charged and your present alternator is keeping it charged, it's doing its job. If you want a system to be as close to perfect as possible and money is no object, replace your alternator when you install the amplifiers.

Extra batteries:
Extra batteries are great if you want to listen to your system with the engine off. While the alternator is charging, the extra batteries will only draw current which could otherwise be going to your amplifiers. For proof, all you have to do is measure the voltage while the engine is running. It should be approximately 13.5-14.4 volts DC. Then turn the engine off and measure the battery voltage again. Now it'll be around 12-12.5 volts. Whenever the voltage at the battery is up around 14 volts, there is current flowing into the battery.

 

^^ True story.

 

Quoting from another ca forum:
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
"Ideally you want both a second battery and a high output alt. The alt makes the power, the batteries are there to stabilize it. A single battery can only handle so much current draw before the float voltage (whatever voltage the alt is charging at) is drawn down to the nominal voltage (12 V thereabouts) It's very little strain on the alt to put the battery back to float voltage unless the battery has been pretty deeply discharged. With the car running and playing music, not test tones, this will pretty much never happen usually even with just the stock alt, since the current draw with music does not average out to a very high draw and is nowhere near continuous.

If you have ever used an air compressor,</TD></TR></TABLE>[in reference to using an air compressor and an impact wrench - which one is more important, the compressor or the tank?]<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote"> it really is a good analogy. The compressor itself is pumps the air into the pressure tank just like the alt keeps the batteries charged. When you demand air from the system, the tank provides the initial hit of air and then the compressor kicks in to maintain the pressure for long term demand and to get ready for the next big demand. The alt and the batteries work in a very similar fashion. The alt provides continuous power to the system, but it does not react well to rapidly changing current demands, the voltage goes all over the place. The batteries act as a buffer to take the bit current hits and keep the alt from having to try to rapidly change output. The overall demand on the alt is actually reduced by having a good buffer in place. A really huge cap (100 or so Farads) would do this if the high ESR of a cap didn't drop the voltage below a usable level before it even leaves the cap.</TD></TR></TABLE>

 

The compressor or the tank, which is more important?
It's a trick question, right?
Seems to me that one is not much good without the other.

Look we know what you are trying to say, however, as most car audio will work with voltages anywhere from 11.5V to 14.5V it's not so much about the voltage as it is about current, amps is what it's about, and your right, kind of, 2 batt. will stabilize the current, however they have no effect on the alt. ability to produce voltage or amperage for that matter, two batt. are a greater load for the alt.

Now if you really want to make a diff. with multiple batt., install two 6V batt. wired in series.

As has been mentioned, more batt. really only do one thing, they extend the play time of a system when the engine is not running, and put a greater load on the alt.

Unless you are looking to extend play time when your parked a second batt. is not the way to go, an upgraded alt. is always the best bet, and should be done if adding a second batt., as the batt. is a load.

Also, [not sure what cars your talking about] but cars that I work with have about 12.5V, [engine not running, 1 or 2 12V batt.] and about 13.5V at idle and up to about 14.5V at higher RPM.
Most car audio I work with do not like voltages much over 14.5V and tend to shut down at 15V, so I am not sure what would happen to them at 16V+. 94

 

My threads were made on the assumption that he is planning on a decent system. Albeit, my version of a decent system is a bit tainted compared to most people's. Either way, that is a BIG assumption. If he's running a typical daily driven system consisting of less than 500 watts, he doesn't need to even think about a second battery. If he's serious about competing or just wants to knock his head off with bass, then he is going to have to consider an extra battery because the current draw of said systems is too much for a single amp, single alt setup.

The 16v reference was for the extreme classes of competition that I mentioned in that post. Most cars can handle 14.4 or slightly over just fine.

All of this is a moot point if he's just talking about a normal system or no system at all.

 

Ask yourself this... your system is drawing 200 amps of current, your alternator puts out 60 amps of current, where does the rest come from? The battery.

Okay... will one battery or two hold a decent voltage for longer? Thats easy, two will.

My SPL truck has nine batteries... my alternators only put out 400 amps and my system can draw over 1200 amps. My voltage takes a substantial amount of time to drop to 12 volts or under. This is because my batteries are supporting the current draw... the truck is RUNNING, but the alts are being overwhelmed.

 

I am running a 130 amp alternator, 1 Kinetik HC1400. I have 3 amps. One Alpine PDX 1.1000 and 2 Alpine PDX 4.150's I am using 7 of the 8 channels on the 2 4.150's so that's a total RMS rating of 2050 Watts. This is a MECA sound quality competition car and we get judged with the engine off. No second battery is needed at all. Even in my Liberty which is also a Meca competition car I have a 160 amp alternator and 1 Optima Yellow Top. Running 1400 watts RMS, Navi, 3 video screens and 6 additional off road lights. No second battery needed.

In reference to SPL setups you cant even compare the 2. You charge up all your batteries before you hit the judging lane and burp a test tone. Most SPL competitors put their cars on a battery charger before and after their run. Not exactly the same as a daily driver.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sqsi &raquo;</TD></TR><TR><TD CLASS="quote">I am running a 130 amp alternator, 1 Kinetik HC1400. I have 3 amps. One Alpine PDX 1.1000 and 2 Alpine PDX 4.150's I am using 7 of the 8 channels on the 2 4.150's so that's a total RMS rating of 2050 Watts. This is a MECA sound quality competition car and we get judged with the engine off. No second battery is needed at all. Even in my Liberty which is also a Meca competition car I have a 160 amp alternator and 1 Optima Yellow Top. Running 1400 watts RMS, Navi, 3 video screens and 6 additional off road lights. No second battery needed.

In reference to SPL setups you cant even compare the 2. You charge up all your batteries before you hit the judging lane and burp a test tone. Most SPL competitors put their cars on a battery charger before and after their run. Not exactly the same as a daily driver.</TD></TR></TABLE>

I drive mine to the show and charge it on alternator power Mine also plays music in the mid 150s on the Term-Lab, so it is comparable to an extremely high current draw daily driver vehicle. At the nSPL show last weekend I burped 158.2 then ran music to demo to a line of people -- truck running. I eventually had to take a break and let the batteries charge, but I was able to stay above 12 volts for a substantial period of time.

I'm sure you also understand that you mids / highs amps rarely put out anywhere near as much power as their RMS rating. Now... clamp those amps all at maximum RMS output continuously and try to do it on one battery, engine off, it won't be so friendly. I test 3000 watt amps on my bench quite often... I have a 60-amp power supply so I use four batteries to keep the voltage in the 12s long enough for a meaningful test -- if I unhooked three of the batteries then the voltage would go into the 10s almost immediatly.

Most people driving around with systems are a bit lop-sided in that they have 3000 watts on their subs and 300 watts up front, thats a bit different Their current draw is a bit higher than yours.

I'm not arguing semantics with you -- the moral of the story is an extra battery will help you, even if your car is running, if you are over-running the capacity of your alternator. Yes, you will need to give it a break for the alt to catch up eventually as the batteries don't make power, they just store it -- but if you jam one song hard then the second battery will keep that voltage at an acceptable level longer than if you didn't have it.

 

I go away for a while and come back to this LOL.

Where's the popcorn?

Let's correct a few statements.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sundownz &raquo;</TD></TR><TR><TD CLASS="quote">Yes, you will need to give it a break for the alt to catch up eventually as the batteries don't make power, they just store it.</TD></TR></TABLE>
Incorrect. Lead acid batteries produce electricity by chemical reaction. There is a continous chemical reaction that occurs. One that happens when you discharge and one that occurs when you charge. A lead acid battery functions similiar to how a AA battery that you buy at the store does. The difference is you can reverse the chemical reaction with a charge.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Electrodynamic &raquo;</TD></TR><TR><TD CLASS="quote">Or you can go on believing that a second battery is good for nothing other than operating your system while the car is off, but that's being a little ignorant. Take a look at ANY SPL sanctioning body and notice the different classes based off of multiple batteries and their locations. There are not only different classes for multiple batteries, but also for extra batteries in non-stock locations. Then there are classes for car-on and car-off. If you want to go even further, look at the extreme (literally) classes in IDBL, MECA, IASCA, etc, and you'll notice that they are all running MULTIPLE batteries and multiple alts...not just a bunch of alts and a single battery. You have to have power (12v to 16v+) to make power in the car audio realm.</TD></TR></TABLE>
This is a silly argument. Batteries are cheap!!! Thats why they have so many fricken batteries duh? They dont need to play there systems for long periods of time. If alternators were cheap and easy to connect 10 of them to a car there would be 10 alternators attached to every car. But the realistic side of the story is they are expensive and it's not easy to hook 10 of them up to a car.

So yes having mutiple batteries is good for nothing other then operating your system with your car off. Once the car is on the only thing making any energy is the alternator.

I might also add the air compressor anology is also silly for multiple reasons. An air compressor tank is nothing like a battery its more like a Capacitor (dont argue you will loose). Secondly anyone ever try to run a sander with a Kmart special air compressor? It will really **** you of, you can sand for a couple seconds then you sitting for 10 min to allow the compressor to fill the tank back up. You could add 10 tanks and you will end up with the same problem. Your initial usage would be extended for a couple seconds (great for SPL) but then you also extend the time to refill by minuetes. Get the picture here? It takes longer to refill (charge) with each extra tank you add. Thus making the actuall time you are sanding go down because most of the time you are sitting waiting for the tanks to fill. You could stop buying extra tanks by investing in a better compressor. Then laugh at the dumb *** that sitting by his compressor picking his nose waiting for the tanks to fill.

If your looking to add extra storage capacity for short periods of time add a capacitor. Then this fits in line with the air compressor analogy. If this doesn't work well, then you have exceeded your alternators capacity and it needs to be replaced.


Modified by nsxxtreme at 9:15 AM 12/19/2007

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">I go away for a while and come back to this LOL.

Where's the popcorn?</TD></TR></TABLE>

There's a new kind out that I bought this week.. Orville Reddenbacher Natuurals. Get the salt & cracked pepper flavor. Mmm.

 

A capacitor is the most worthless thing mentioned yet, 1 farad is only enough energy for a few microseconds. Car audio caps as they are sold currently are worthless -- the way RF managed caps in their 15kw amp is much more useful, albeit extremely expensive.

Point is... yes, multiple batteries won't indefinitely increase your useful play time with a continuous level of high current draw -- but when you have multiple batteries you can stay in the 12s range longer for an extended high current situation -- for instance, jamming hard on your favorite song.

After that, yes, you need to let them charge back up. If you had only one battery you would have much more quickly dropped under the 12 volt range.

If you like I can take a video for you on my test bench of one battery + power supply and then four batteries + plus supply to show you that the one with four batteries will indeed remain at an acceptable voltage level longer. I'm not talking about maintaining the full 14.4 volts, but staying in an acceptable range (eg: in the 12s).

And yes, when the high current draw is over it will take time for the alternator (or power supply) to catch back up.

Cheap batteries? The ones I use cost as much as an HO alternator I'm adding two more alternators (four total), but yet I will retain my large battery bank. Why? I can play it longer at high current beyond alternator capacity before I need to let the bank charge up again -- I let it rest when I dip under 12 volts. It's directly analogous to a normal street beating vehicle, albeit scaled up dramatically... as my system does indeed play music in the 150s range for several minutes at a time.

Now would it be *better* to have enough alternator capacity to keep up? Sure it would. Fact is, that is quite often not possible -- as is my situation and the situation of many Honda owners running several thousand watts. An extra battery can help maintain a safe voltage (in the 12s or high 11s) for a longer period of time once alternator capacity has been exceeded -- this is a fact.

 

What's wrong with running 4 guage wire to reloacte your battery? What else do you have to do?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CRJenkins13 &raquo;</TD></TR><TR><TD CLASS="quote">What's wrong with running 4 guage wire to reloacte your battery? What else do you have to do?</TD></TR></TABLE>

I would say that it would be best to run a larger cable for such a relocation for the lowest voltage drop possible. I had a CRX years ago with a relocation and 1/0 cable was used.

As for the OP... I would use one big one, a good one like a Powermaster XS sport.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sundownz &raquo;</TD></TR><TR><TD CLASS="quote">A capacitor is the most worthless thing mentioned yet, 1 farad is only enough energy for a few microseconds. </TD></TR></TABLE> Capcitors aren't worthless (when used correctly) and most made today are pretty damn good.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sundownz &raquo;</TD></TR><TR><TD CLASS="quote">Point is... yes, multiple batteries won't indefinitely increase your useful play time with a continuous level of high current draw -- but when you have multiple batteries you can stay in the 12s range longer for an extended high current situation.</TD></TR></TABLE> Honestly WTF are you talking about? Do you even know? With a properly sized alternator you could sustain 14.4V longer in an extended high current situation longer then any multiple batteries ever could.
You just stated two statements that contradict each other.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sundownz &raquo;</TD></TR><TR><TD CLASS="quote">
Cheap batteries? The ones I use cost as much as an HO alternator</TD></TR></TABLE>
If your batteries cost as much as an HO alternators what's the use of the batteries?
Once the car starts the Alternator sources all the energy. And if your exceeding the limits of the alternator and the cost is the same as a battery then it makes more sense to add an alternator

Ahhh...but now we get into the area where the average stereo monkey doesn't understand the magical Capacitor. A voltage regulator in a charging system can only respond so fast. Which means the voltage will dip until the regulator detects the dip and supplies more energy. Here is where the Capacitor comes into play it can dump a tremendous amount of energy extremly fast (yes fster then a battery)but over a short period of time. This is why adding one will minimize headlight flickering.

Secondly what makes you think an amplifier needs 12V? Does it magically shut off or explode when the voltage drops below 12V LOL? Most of todays amplifiers are regulated meaning they take anywhere from about 9V-20V on the input and then bump this up to 33V on the amplifier stage. It doesn't matter where that voltage moves between 9V and 20V the amplifier stage will see a steady 33V.

Finally why would you waste your time with adding a second battery when
1) it will rob current that could be going to your stereo
2) Once run down it will take longer to charge
3) Most people aren't in SPL competitions where they could compete even without an alternator.
4) you cant sustaine your power levels

 

Dammit, why do you guys have to do this when I'm at work? There is no popcorn at work