Printer Friendly Forum Posts - 2 car batteries?

I'm a little confused, but worried at the same time. My friend has 1 12" Kicker L7 in his Blazer, and supposedly it sucked all the juice from his battery. So, he got a 2nd battery put into his car. I'm curious as to if this is necessary if you have alot of power? Say 2 12" CVX's pushing 1500 rms @ 1 ohm? I don't want to risk buying something and then finding out that it just sucks all of my battery...

The Alternator charges the battery. If you don't generate enough power the battery will not get charged and fail. Adding a second battery just made the problem worse. Now the Alt has to work that much harder to charge two batteries. Chances are that Alt will smoke soon. Not sure how long the batts will last.

A HO Alternator is where the money needs to go.

Battery type? He should only need 1 battery for one 12.

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I would add a second car battery only if you are planning to upgrade your alternator. If you do upgrade, batteries should be identical also close to the same purchase date if possible. I had bad experiences with optima yellow top car audio batteries, i would go with something else, just my opinion.

"Battery type? He should only need 1 battery for one 12."

The type of battery makes no difference. Yes the AGM might charge faster but energy is not being created.

So an 18" needs two batteries? If your amp is wired to 4 ohms the amp doesn't care how many speakers are connected. The Amp(s) wattage and efficiency determins the number of batteries not the number or size of driver.

Optima isn't my first choice.

I like the XS power battery's better then the Optima but that's just me.

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(power acoustik system)
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2 batterys, 1 power

I think it sucked all of his juice while the car wasn't running. But, I think I may stick with CVR's. Those shouldn't need anything special. Maybe go with Alpine Type-R's. Suggestions on that one?

audiocableguy wrote:

"Battery type? He should only need 1 battery for one 12."

The type of battery makes no difference. Yes the AGM might charge faster but energy is not being created.

So an 18" needs two batteries? If your amp is wired to 4 ohms the amp doesn't care how many speakers are connected. The Amp(s) wattage and efficiency determines the number of batteries not the number or size of driver.

Optima isn't my first choice.

Kind I should say? If optima's isnt your first choice, then type/kind matters to you, no? Stock Nissan battery drains in 2 songs with 1 12", discretion with yellow top hasnt died yet. I would think that the energy needed pushing 2 15's would be greater then the energy required by 10's. So, 12 boat speakers all flexin for 1 hr uses the same battery power as 4 speakers in 1 hr as long as ohm's are the same?

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You can run 1000000 speakers on the right amp with 1 battery. The number and size of the speaker has nothing to do with the amount of batteries, the size and efficency of the amp do.

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"Stock Nissan battery drains in 2 songs with 1 12", discretion with yellow top hasnt died yet."

If your loosing battery in less than 5 minutes you have a bad battery and or faulty charging system. Just because the Optima has more run time doesn't mean it's a better battery, just means it has more capacity or maybe just newer.

"12 boat speakers all flexin for 1 hr uses the same battery power as 4 speakers in 1 hr as long as ohm's are the same? "

Yes.

"I would think that the energy needed pushing 2 15's would be greater then the energy required by 10's."

Pretty basic stuff, electronics 101. It concerns me you are posting advise not knowing this stuff.

ianarian wrote:

I would think that the energy needed pushing 2 15's would be greater then the energy required by 10's. So, 12 boat speakers all flexin for 1 hr uses the same battery power as 4 speakers in 1 hr as long as ohm's are the same?

Ohm's Law. Do you know what that is? How about Kirchoff's current law?

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Thats nuts, there is a open circuit in my head. Lights not on. Without thinking it through, I was under the belief that you can drain a battery quicker with 2-15's on a 1000w amp quicker than you could 12" with the same resistance on the same amp. So, with 500w X 2ch stereo 4ohm amp, matched I/O levels with the source(gain), at half volume, your Memphis Reference 12's are maxed out. Say your drawing peaks of 40 amps. Lets pretend they're SVC 4ohm. Then you throw in your Diamond Audio DVC 2ohm/series(4ohm) 15's in and notice you can turn the volume up twice as much, then your drawing peaks up to 80 amps. What am I missing? I'd like to re-study or learn the comprehension behind this.

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posted_image Go ahead and install the equipment you want...Amp,Subs,Etc...Make sure you do "The Big 3" upgrade before you install the amp....(just do a forum search on the big 3) It looks like this might get a lettle ugly...! So post what equipment your defitnely installing... (Are you going to install this stuff yourself...Or have a shop do it...?) Once you install the equipment and properly tune/set gains,and do THE BIG 3 upgrade...Lets get a meter on there and see what your voltage is dropping to...Have you put any thought into the enclosure/box the subs are going in...? Lets also make sure you are installing the correct size power wire...And the point at which you ground the amp is soooooooooooo important!!!!!!!!! My advice is to make a decision on the equipment...But dont cheat yourself on the amp kit or box...!

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M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

(2) 4 ohm 1" tweeters will draw the same power as (2) 4 ohm 18" subs when hooked up the same way to the same amp. The amount of power has to do with the overall impedence of the load, not the amp or size / shear number of speakers.

As far as the battery question, like somebody already said if there isn't enough current being generated a HO alternator would be the correct way to go. However, install your equipment first, do the big 3, and then feel it out. No use putting money where it isn't needed.

I would recomend a "performance" battery over a stock battery any day - the construction of the battery can determine how efficiently it charges, which can turn more current from the alternator in to stored power instead of heat.

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Kevin Pierson

livinloud247 wrote:

I'm a little confused, but worried at the same time. My friend has 1 12" Kicker L7 in his Blazer, and supposedly it sucked all the juice from his battery. So, he got a 2nd battery put into his car. I'm curious as to if this is necessary if you have alot of power? Say 2 12" CVX's pushing 1500 rms @ 1 ohm? I don't want to risk buying something and then finding out that it just sucks all of my battery...

Is this your current set-up...? Are you having any dimming issues...? Or Is this just the set-up your considering...? What amp is it exactly...? Some shops will throw a 2nd battery in b/c thats what the customer wants...Some do it as just an up-sell...For the most part adding a 2nd battery is part of process that should be completed ...Like adding a 2nd battery is step 3 but you missed steps 1-2-4-5...Follow me...? And as Kp said which took me 2 posts and 4 edits...Install...Feel it out...Defitnely upgrade battery under hood...!(also big 3)

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M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

ianarian wrote:

Thats nuts, there is a open circuit in my head. Lights not on. Without thinking it through, I was under the belief that you can drain a battery quicker with 2-15's on a 1000w amp quicker than you could 12" with the same resistance on the same amp. So, with 500w X 2ch stereo 4ohm amp, matched I/O levels with the source(gain), at half volume, your Memphis Reference 12's are maxed out. Say your drawing peaks of 40 amps. Lets pretend they're SVC 4ohm. Then you throw in your Diamond Audio DVC 2ohm/series(4ohm) 15's in and notice you can turn the volume up twice as much, then your drawing peaks up to 80 amps. What am I missing? I'd like to re-study or learn the comprehension behind this.

Two 12" 4-ohms speakers and two 15" 4-ohms speakers will place the same effective load on an amplifier. Of course if you change the loading you will change the current draw. Like I said, Ohm's Law. It is difficult to know if that's what you are even talking about, however....

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livinloud247 wrote:

I think it sucked all of his juice while the car wasn't running. But, I think I may stick with CVR's. Those shouldn't need anything special. Maybe go with Alpine Type-R's. Suggestions on that one?

Not sure how this happens either. Depending on how the amp was wired, there should be no current draw with the radio off. Was the key on accessory with the car not running?

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Big Al

"It is difficult to know if that's what you are even talking about, however.."
Forgive me Dyohn, I cant get this answered anywhere else...

I can play my single 12" on my system for hours without the battery dieing. Sometimes at events I disconnect the 12" sub. I have wires pre-ran in flex tubing to the bed of the truck where I play 2-Diamond Audio 15's with the same amp. With the 15's I can turn the volume and sub level up higher than the 12". The battery will die within 1 hour. By "die" I mean, no longer enough power to start the truck. Why is that?

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ianarian wrote:

"It is difficult to know if that's what you are even talking about, however.."
Forgive me Dyohn, I cant get this answered anywhere else...

I can play my single 12" on my system for hours without the battery dieing. Sometimes at events I disconnect the 12" sub. I have wires pre-ran in flex tubing to the bed of the truck where I play 2-Diamond Audio 15's with the same amp. With the 15's I can turn the volume and sub level up higher than the 12". The battery will die within 1 hour. By "die" I mean, no longer enough power to start the truck. Why is that?

First off, more volume = more power so by simply turning the radio up theoretically you will increase current draw.

Second, how many ohms is your 12" sub and what is the ohm load of the 2 15s? If the 2 15s together have less impedence then the 1 12" sub you will increase power again.

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Kevin Pierson

"First off, more volume = more power so by simply turning the radio up theoretically you will increase current draw."

theoretically we could write that that in stone

"Second, how many ohms is your 12" sub and what is the ohm load of the 2 15s? If the 2 15s together have less impedence then the 1 12" sub you will increase power again"

The 15's are both DVC.2 ohm, the 12" is a DVC.4 ohm.

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And how are you achieving the same load...?(subs wiring)

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M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

ianarian wrote:

The 15's are both DVC.2 ohm, the 12" is a DVC.4 ohm.

You say you are an electrician in your profile and you can't comprehend this?

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Comprehend WHAT? I got 2 wires from my amp that have a minimum resistance rating of 4 ohm. I got two 4 ohm coils on the 12". Need I say more? Then I have two 2 ohm coils on each 15, wired IN SERIES, need I say more? SO, if more volume draws more current, 15's handle higher volume than the 12. They drain the battery quicker. THUS' SPEAKER SIZE IS RELEVANT to how long the battery can last. The amount of power dissipated from you average 12" sub, should not need upgrades to the ALT or the big 3. If his battery took a dump when using only 1 12" sub then the fault lies on him or the battery. THATS assuming everything else in the system is in order.

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So tell me what impedance your two 12" DVC 4-ohms speakers are presenting to the amp. Now tell me what impedance the two DVC 2-ohm speakers are presenting to the amp. Lets' see: DVC 4-ohm loads wired in parallel at the speakers creates a 2-ohm load, and wired in series creates a 8-ohm load. How are these wired and how are they wired to the amp? Each DVC 2-ohms speaker wired in series presents a 4-ohm load. How are these two wired to the amp? Are the two sets presenting the same net loads on the amp? No? Yes? You tell me.

If the load from both sets of speakers is the same, and if the volume level on the receiver is the same, the current draw from the amp will be the same. So, in your case yes I agree "something else" is certainly happening, and by something else I mean it ain't the same load in both cases.

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ianarian wrote:

SO, if more volume draws more current, 15's handle higher volume than the 12. They drain the battery quicker. THUS' SPEAKER SIZE IS RELEVANT to how long the battery can last.

No, speaker size is NOT relevent. In your specific case, it is, but I have seen 10" subs with higher power ratings then 15" subs, so to solely base power consumption off speaker size is impossible.

You need to analyze each case individually and base your design off RMS power of the amplifier(s) and the type of amp(s). The amount of power output and the efficiency of the amp will ultimately determine how long a battery will last.

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Kevin Pierson

"The amount of power dissipated from you average 12" sub, should not need upgrades to the ALT or the big 3."

You need to be thinking in terms of wattage, not speaker size. The amp determines the upgrades not speaker size!. You might be running a bridged Zapco C2K-9.0 on a single 12". Upgrade, Yes. Alpine PXD-1000.1, maybe. Power Acoustic, why bother IMO.

Say you had an A/B switch and a current meter. All things be equal: Switch between a 15" and a 12" speaker and the amp current will not change. Will one be louder? if the efficiency is different, Yes.

"SO, if more volume draws more current, 15's handle higher volume than the 12."

More volume draws more current, Fact.

"15's handle higher volume than the 12"

I have no idea how you could arrive at such a statement. The 15"s might be more efficient therefore play louder than the 12". It's not handling higher anything. Plus you are comparing two drivers to one.

"THUS' SPEAKER SIZE IS RELEVANT to how long the battery can last."

This is just a flat out false statement. No matter how you try to reason it out it just isn't going to happen. As said multiple times wattage, voltage and efficiency of the amp determine what your electrical needs are. Speaker size has nothing to do with it and never will.

First off, everyone who commented I thank you very much. If there was a better source for info available, I would be bugging that and not you all.(too bad huh?) posted_image

Im not afraid to ask questions though. I believe things based on reason. Some people dont care how it works, as long as it works...I wish I was like that. I often comment to see if my opinion or research can be validated or inconclusive. Better to ask and be uncool, than not know and be cool! Iaqnarian Law-states: the (#/posts) divided by (#/members) it takes to sink a concept into the brain. Thanks again...gentlemen, humblest of apologies,....until next time!!!

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ianarian, it's not about being uncool. These forums are for people to seek advice and ask difficult questions. It's about you giving out advice to others that sometimes is wrong, and then demonstrating in some of your posts and that you seem to lack a basic understanding of "how things work." That's cool, come here to learn, but please don't offer advice to others unless you are sure you know what you're talking about. Thanks!

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I hear ya Dyohn. But I know what Im talkin about, its all yall that dont get it. posted_image

No, what I meant in the beginning was: I've seen less than 500w push that 12 just fine. However their L7-15's and solo 18's are not as forgiving. Now my 15's can be replaced with 8's and still be able to have same effect on my battery that I was talking about. When I was referring to speaker size, it was based off the fact that this guy's L7 can be ran fine on a good battery without changing alternators and a bunch of other things like that. Anything bigger than a 12 I would not recommend to take any shortcuts on power.

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ianarian wrote:

I hear ya Dyohn. But I know what Im talkin about, its all yall that dont get it. No, what I meant in the beginning was: I've seen less than 500w push that 12 just fine. However their L7-15's and solo 18's are not as forgiving. Now my 15's can be replaced with 8's and still be able to have same effect on my battery that I was talking about. When I was referring to speaker size, it was based off the fact that this guy's L7 can be ran fine on a good battery without changing alternators and a bunch of other things like that. Anything bigger than a 12 I would not recommend to take any shortcuts on power.

And that's not a fact, it's just wrong. The size of the speaker has nothng to do with the load it will place on your electrical system. It's the amplifier that does that, and the load placed on the amplifier by the voice coil impedance.

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ianarian wrote:

But I know what Im talkin about, its all yall that dont get it.

We get it, we understand what you are saying, it's just wrong!

Here's another example:

ianarian wrote:

Anything bigger than a 12 I would not recommend to take any shortcuts on power.

This just proves you should not be giving advise.

ianarian wrote:

However their L7-15's and solo 18's are not as forgiving.

Are you talking about efficiency here or what??? Read all the above posts that aren't yours and you will see the facts don't change.

David, Kevin and Jeff have all given you correct info. I have given several straight forward examples. You are going against established electronic/electrical principles, basic electronic 101 stuff here. No matter what excuses you have or beliefs you have, you are incorrect.

Here's another example:
ianarian wrote:
Anything bigger than a 12 I would not recommend to take any shortcuts on power.
This just proves you should not be giving advise.

Ya, because I have no law to prove that the effect of running different size subs on only 25% of their rms rating is less pronounced to the ear on smaller subs then on larger ones. And if you did, the larger sub of same brand same series will drain the battery quicker. In that case, Im glad I learned this before I learned the theory.
Here is a vid of a Cerwin VMAX.4 12". The beginning reading, was from just putting my hand close to the speaker, then just barely touching it and when the numbers are jumping I was pressing in on it.
https://www.youtube.com/watch?v=siYU3I4s5P0
If I had a mechanical hand with the same electrical properties as my hand and replicated the same exact movements on a 12 and a 15, those numbers will read the exact same?
Here is a unclear vid (for your viewing enjoyment)of me testing the sound in the new box at minimum gain levels. (Notice only a 2 db increase from windshield to right in front of the port)
https://www.youtube.com/watch?v=on84hDbnQTk
Now, the 2ohm attempt is not advice I would give to someone. I did however drive all the way to L.A.(6-7hrs one way) testing every type of music and then some.(Notice the fan I installed to combat the heat this things going to be creating.) Now if I asked if I could run a 4ohm stereo 2 channel amp bridged at 2 ohms, we would all(including me) say "no way dont do it". You'd pull out the ohm card again for proof. AAAAAAH YA, well here I have done it again. The amp is stable!! Thanks
posted_image

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