batteries or caps?

would u say it is better to run a second battery in the trunk specifically the new kenetic battery with a 200 amp relay/isolator under the hood or would u say to use a couple of caps in the trunk, or both. many people have a lot of different ideas how a cap works. what and how does a cap really work. to my knowledge i was lead to believe that it makes sure the amp has full voltage at all times. obviously the first thing people always used to say was it helped dimming of the lights which to me is not true. only an alternator upgrade seems to take care of that problem.

-------------
alarm king

Big 3, first. Then, high output alternator, ONLY. Then a second battery (identical to the first one, which means you are buying two). In that order, and you'll notice I made no mention of caps or isolators.

-------------
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Doesn't a second battery need to be isolated from the main starting battery? Otherwise they'll kill each other off? That's what i've always seen.

-------------
Soldier: This is the worst part. The calm before the battle.
Fry: And then the battle is not so bad?
Soldier: Oh, right. I forgot about the battle.

It doesnt "need" to be isolated, but i alway suggested it to all my customers and have the secondaries isolated. I just like having the ability to play the system and not have to have the truck running or worry about the truck not starting. But if you do isolate them be sure to fuse before and after the isolator.

As far as the alternator, i am still running the stock alt powering the running batt and 2 secondaries for almost two years now. I wouldnt suggest this because YES it is going to kill the alt but at that point i will upgrade. But for most vehicles this isnt going to work unless its a truck or something with a larger alt.

-------------
2007 Acura TSX
SQ setup in the works

i have to agree with haemphyst..... caps are mostly hype... not worth the price of admission most times..... do the big three and u will be in better position to bump hard and do it for a long time... and your equipment will thank u for it.........

********smacks himself***********

don't mind me... i'm just hung over........

-------------
there can be only one.......

If your alternator is big enough to handle both batteries no isolator is needed.  The batteries won't kill each other because once they equalize there will be no difference in potential so no electrons will flow between them.

The problem most people have is they arn't willing to spend the money for a bigger alternator, so they throw a 2nd battery on the OEM sized alternator, causing it to strain. 

-------------
Kevin Pierson

KP]The wrote:

---

batteries won't kill each other because once they equalize there will be no difference in potential so no electrons will flow between them.

---

I'm confused.

Doesn't "equalizing" mean that the battery with the lower ESR drain off the other one - and - uhh - kill it?

jville wrote:

---

i am still running the stock alt powering the running batt and 2 secondaries for almost two years now. I wouldnt suggest this because YES it is going to kill the alt but at that point i will upgrade.

---

Are you kdding? Two years?  If this was going to kill the alt it would have done so already.  Hooking two (or three!) charged batteries up to an OEM alt doesn't strain it any more than one does - this depends on amperage demanded of the batteries - not just having two hooked up.

I want you to know dude - I've been hammering away at this point - much to my popular deteriment - on this board for years.  Your sig confirms it, HO alts are totally worthless - what matters is current at 12.5v, everything else is a red herring. 

-------------
"I'm finished!" - Daniel Plainview

sedate wrote:

---

KP]The wrote:

---

batteries won't kill each other because once they equalize there will be no difference in potential so no electrons will flow between them.

---

I'm confused.

Doesn't "equalizing" mean that the battery with the lower ESR drain off the other one - and - uhh - kill it?

---

No, it means that if battery A is 13.654 volts and battery B is 13.652 volts (and they are identical batteries) then battery A will charge battery B to around 13.654 volts.  At that point, both power supplies are equal, and since there is no difference in potential no current will flow.  It's the same concept of installing a cap (a power storage device).  Once the two power storage devices stablize then no current flows.

-------------
Kevin Pierson

sedate wrote:

---

jville wrote:

---

i am still running the stock alt powering the running batt and 2 secondaries for almost two years now. I wouldnt suggest this because YES it is going to kill the alt but at that point i will upgrade.

---

Are you kdding? Two years?  If this was going to kill the alt it would have done so already.  Hooking two (or three!) charged batteries up to an OEM alt doesn't strain it any more than one does - this depends on amperage demanded of the batteries - not just having two hooked up.

I want you to know dude - I've been hammering away at this point - much to my popular deteriment - on this board for years.  Your sig confirms it, HO alts are totally worthless - what matters is current at 12.5v, everything else is a red herring. 

---

This is an exception, and not a rule.  All cars are different, and most alternators are different.  If you put three charged batteries in the vehicle I would agree that at first there would be minimal load added.  But, as you draw current away from the batteries at a rate faster then the alternator can charge you'll stress the alternator.  Heaven forbid you leave the lights on for 30 mintues with the car off (or listen to the radio with the car off).

Now, your alternator has 3x the load to charge back up, which will make it work 3x harder.  It's simple math if you have a 100 amp alternator and a 150A load eventually you're going to have problems.

-------------
Kevin Pierson

KP]No, wrote:

---

it means that if battery A is 13.654 volts and battery B is 13.652 volts (and they are identical batteries) then battery A will charge battery B to around 13.654 volts.  At that point, both power supplies are equal, and since there is no difference in potential no current will flow.  It's the same concept of installing a cap (a power storage device).  Once the two power storage devices stablize then no current flows.

---

Huh.  Okay - I'm not trying to argue, just looking for a more complete explanation (and you do have that "i" and that third star) - but how does the ESR thing play into this?  Is this too a red herring?

KP] ba wrote:

---

tery B is 13.652 volts (and they are identical batteries)

---

I guess this is the biggest issue I have with your explanation - you take careful pains to paranthetically state "(and they are identical batteries)" - is that you don't explain why they 'equalize' with identical batteries, but you avoid what happens when diffferent batteries are used or how this impacts your logic here.  I feel this is a wholly incomplete explanation that, as stated, is full of holes.

-------------
"I'm finished!" - Daniel Plainview

KP]But wrote:

---

as you draw current away from the batteries at a rate faster then the alternator can charge you'll stress the alternator.  Heaven forbid you leave the lights on for 30 mintues with the car off (or listen to the radio with the car off).

Now, your alternator has 3x the load to charge back up, which will make it work 3x harder.  It's simple math if you have a 100 amp alternator and a 150A load eventually you're going to have problems.

---

WHAT?!?!

None of this makes ANY sense. 

From this logic a 40watt bulb put to three seperate batteries draws the same amount of current from each battery that it would require from a single battery!?!?!

Like you say - simple math - now I'm REALLY confused. . . . .

-------------
"I'm finished!" - Daniel Plainview

Hey!  When did I get an "I"????

When explaining theories you always try to assume everything is identical.  The drain (or bleed) characteristics of the batteries may be different which may make a small battery that can't hold a charge for very long appear to be leeching off a large battery with a long storage capacity.  If you have to identical batteries you can assume they will discharge at the same rate and you can assume that the voltage will drop from each battery at the same rate, so no leeching effect will be present.

The ESR of the system will be reduced by wiring the batteries in parallel, so you might actually see an advantage in that department.  The ESR deals with resistance of components in series - well when you double the capacity of the storage devices the resistance will drop (what happens if you wire two 8 ohm sums in parallel - you get 4 ohms).

Let me try to explain what I was getting at a little better above.  If you have a battery at 14vdc and another battery at 10vdc and you wire them in parallel you will have a 4vdc difference in potential.  The 14vdc battery will power the 10vdc battery.  As the 10vdc battery receives current from the 14vdc battery its voltage level will rise, while the voltage level of the 14vdc battery drops.

Eventually they will settle at ~12vdc, at which point there is no more potential (12vdc - 12vdc = 0vdc), and with out potential current can't flow, so you'll have the equivalent of an open circuit.

-------------
Kevin Pierson

sedate wrote:

---

KP]But wrote:

---

as you draw current away from the batteries at a rate faster then the alternator can charge you'll stress the alternator.  Heaven forbid you leave the lights on for 30 mintues with the car off (or listen to the radio with the car off).

Now, your alternator has 3x the load to charge back up, which will make it work 3x harder.  It's simple math if you have a 100 amp alternator and a 150A load eventually you're going to have problems.

---

WHAT?!?!

None of this makes ANY sense. 

From this logic a 40watt bulb put to three seperate batteries draws the same amount of current from each battery that it would require from a single battery!?!?!

Like you say - simple math - now I'm REALLY confused. . . . .

---

Not at all.  The lightbult will draw the same amount of current regardless of the device feeding it.

Say you have one battery with a storage capacity of 50A (not even the correct way to rate a battery, but it makes it much easier).  Say you have an alternator thats rated at 150A.  Now, assume the car and the radio together, at max load is going to draw 175A.  At first, you will be fine, as you have the 150A the alternator is providing and you have the reserve capacity of the battery (50A).  But, eventually you'll drain the battery, and you'll be left with only the 150A the alternator can provide.  At that point the car starts hesitating, the radio starts cutting off, etc. so you turn the radio off, dropping the load on the system to 100A.  However, in addition to the load of the car the battery, being drained, is now a load and will consume 50A to charge back up, giving you a 150A load on the alternator.

Now run the same scenario but increase your storage capacity of the battery by 3 (to 150A).  Sure, the system will play longer as it will take longer to drain the electrical system, but once you do drain it you now have to charge up a 150A load (three batteries in parallel) PLUS power the car.  So, at this point, even with the radio off you have the 100A that the car needs to function and you have the addional 150A that the batteries require to charge.

The point is that a battery that has less potential then the output of the alternator will be a load on the alternator.  The bigger the battery (ie the more storage capacity) the more power its going to take to charge it.

I'm trying my best here to explain it!

-------------
Kevin Pierson

KP]Eve wrote:

---

tually they will settle at ~12vdc, at which point there is no more potential (12vdc - 12vdc = 0vdc), and with out potential current can't flow, so you'll have the equivalent of an open circuit.

---

Okay - so by ur logic the idea of identical batteries is irrelevant - b/c they always 'equalize' - so why did you parentheically state "if they are idenctical" . . . ?

KP]I'm wrote:

---

trying my best to explain it!

---

You'll be digging deep before I'm done with ya. . . . .

-------------
"I'm finished!" - Daniel Plainview

To cover my butt.  If someone mixes a Red top with a Yellow top I have no idea what would happen, as they use different cell technology.  Manufacturers are always saying that they don't recomend mixing battery types in an installation, and that is all I was trying to do.  Whenever using multiple batteries it is good practice to use identical batteries.

That, and who would ever buy two identical brand new batteries and try to prove me wrong?  :)

-------------
Kevin Pierson

Either i have been lucky or have proven alot of people wrong. I have bought all three batteries at different times and yes mixed Starting cell and deep cell technologies and have yet to have a problem. All ran off of a STOCK ALT from 2001.


And as far as leaving a light on it would be no problem...just jump the front battery for about 20 sec and it starts right up. the PAC200 keeps them all separate and happy!

So my vote again Batteries. Unless you drive a car with an 80amp alt. Then your in a bigger problem. But in no Serious car audio system should thier be caps! not even for lighting or effect...if you want to do that get some LEDs off ebay for $20 and wire them in! ;)

-------------
2007 Acura TSX
SQ setup in the works

So you do have an isolator?  The isolator will prevent the alternator from seeing the entire load at any given time, which will reduce the loading effect, but require longer time to fully charge all batteries.

Do you have a single PAC200 isolating your main battery from your two additional batteries?

-------------
Kevin Pierson

Hi,

Interesting thread. I've been doing high end stereos on boats for about 2.5 years now and we have been using deep cycle and starting batteries on boats without any problems. We have a PAC200 in there to keep them separate when the boat is in a cove (and off) or something so the boat starts without any problems. The amps are ran off the deep cycle battery while the rest of the boat remains on the regular battery. My understanding is that if two batteries are used that the battery with the lower voltage will make the battery with the higher voltage drop a little. We have never had problems with batteries killing each other though because they are of different cell types.