power cable

[AR 228]

i am putting a second battery in the trunk of my chevy lumina while keeping the one under the hood. I have been told to get some welding wire and hook the one in the truck to the one under the hood and to just keep the ground short. I am wanting to know what other people think of this and if they disagree, what they would recomend.

I am running a 29 LTD Clasic and a Texas Star 667v and the second battery is just to help out.

['Doc]

That's the basic idea for batteries in parallel. A very good idea is to use the largest cable you can find. That reduces the resistance and therefore the amount of voltage lost to that resistance. That 'large' really does mean LARGE! Using the vehicle's metal body/frame for the return line is quite common and works fine.
A good idea is to put a battery 'isolator' in that line going to the 'trunk' battery. They are so that if that second battery get's really low that the first battery isn't drained too. Unless you just wanna have to have a dead battery(s) when starting your Lumina...
- 'Doc

[maters]

Get some welding cable, multi strand , and run from your under hood to the trunk. Most newer cars have a plastic access next to the door sills. If not , go under the carpet.
**** FUSE THIS LINK ******

Run a 4 gauge from the alternator to your under hood.

The one in the trunk should have a short ground.

Don't freak when you motor loads a lot more than before. The alternator can now drag the amps it needs.

[PeteRob]

i am putting a second battery in the trunk of my chevy lumina while keeping the one under the hood. I have been told to get some welding wire and hook the one in the truck to the one under the hood and to just keep the ground short. I am wanting to know what other people think of this and if they disagree, what they would recomend.

I am running a 29 LTD Clasic and a Texas Star 667v and the second battery is just to help out.

Greetings, Pete here...What I did was purchase a 12 volt Interstate Deep Cycle battery and put it in the truck. Next, I purchased a Battery Isolator so my altenator could charge my starting battery and the deep cycle battery. The battery isolator prevents the two batteries from "talking" to each other so my radio and amp could not run down my starting battery leaving me stranded, yet allowed the alternator to keep both charged. Also, because of the use of the isolator I was able to run only a #4 stranded copper wire back to the trunk to charge that battery and use the same size wire for a very short ground to chassis.

This setup allows me to operate my radio and amp off the deep cycle battery only and does not put extra wear and tear on the charging system and you won't have to use large #00 or similar cabling. Do a search on the difference between starting and deep cycle batteries, then ask about battery isolators. I believe you will find this will be your best set-up..

Good luck,

Pete

[AR 228]

I will be running my radio and amp off the battery under the hood and as for the battery in the truck, it is just to help out the first. It is to keep the amps up and voltage a bet higher as well. So that when i put the trigger more voltage and amps are going the the box. I have a 200 amp alternator and a TS 667v that only requires about 65 amps to run and the car only 105 amps. So was it stands now I am fine. But like I said the other battery is to help things out, so that my lights will dim less.

As for as the battery isolators, were and how would I hook one up and what would you recommend for my set up. Also I so have a 4 gauge wire going form the alternator to the battery.
Thank you for the comments

[drdx]

Make sure, as mentioned, you fuse both ends of that big cable. If one end is loose, and something gets through the insulation at any point, you have a problem on your hands. I use those car stereo switchable breakers at each end on mine. I don't use an isolator but for best results it is recommended that you use 2 of the same type batteries and of the same age if possible, but I've seen many not follow that and do well. It is nice to be able to switch the rear out of line, that's where the breakers are handy. I have my rear disconnected when not in use and it has saved me more than once after leaving a dome light on overnight. It is like having a battery jumper box right in the trunk in that case. You 'd probably be better off trying to run the amp from the 2nd battery so upon keydown there isn't a voltage drop as the radio and amp share the same battery, causing less performance from both- divide and conquer so to speak, but with the reserve amperage you have on hand you should be more than fine.

-drdx

[PeteRob]

I will be running my radio and amp off the battery under the hood and as for the battery in the truck, it is just to help out the first. It is to keep the amps up and voltage a bet higher as well. So that when i put the trigger more voltage and amps are going the the box. I have a 200 amp alternator and a TS 667v that only requires about 65 amps to run and the car only 105 amps. So was it stands now I am fine. But like I said the other battery is to help things out, so that my lights will dim less.

As for as the battery isolators, were and how would I hook one up and what would you recommend for my set up. Also I so have a 4 gauge wire going form the alternator to the battery.
Thank you for the comments

Yeah I see what you are saying, but...the beauty of the battery isolator and a 220 amp/hour deep cycle battery is that my headlights and so on don't dim anymore...with a 200 amp altenator it will send power to the deep cycle battery almost constantly as you use the battery. A starting battery is made for starting...not heavy amp use for long periods...such as using a radio and high output amp....that's why I said check out the diffs between them..

As for the isolators...they are easy to install...you can purchase one at almost if not all auto parts store...they are amp rated and I would recommend the wiring install kit to go with it...it makes it even easier to install...

One other thing...if after you research all this...please make sure you fuse the charging line for the deep cycle battery. You should use an ANL type fuse that is rated 125% of your amp draw from your amplifier...example..if you have a 100 amp amplifier..you want to use a 125 amp ANL fuse....Place this fuse inline as close to the deep cycle battery as possible or right on the battery itself...Good Luck...no matter what you decide,

Pete

[MuskyHunter]

Why do you need the 2nd battery? If you need more than one battery for the little 667 then you need to change alternator. I'm running an 8 pill and a driver off 1 battery and never go below 13.6v. With the 1x4 and a factory 165 alt it never went below 13.7v unless I was idling and long winded. Still never hit 13.0. How much of a volt drop do you have now? You might be able to just increase cable size with your current setup. Don't forget that extra battery will also pull current, and once it dips below 12.8v it can pull 10+amps. 2 gauge wire minimum for alt to batt. The isolator will pick up a d+ signal either from the alt itself if it has that connector or you will pick it up off of your fuse block that only has power when the vehicle is on. On the alt it's sometimes called the ign or sensing signal pick up. 105 is a small alt can't go wrong but bumpin it to 140 or more as long as your computer is ok with it.

[p38]

go too walmart and find your way too the radios and look for a capacitor. its cheaper and less stress. get an amp kit as well for the power lead. it will draw on the capacitor instead of the battery. I've done many audio systems! make sure too have a good ground otherwise you will kill your battery.

['Doc]

I don't intend to get into the 'capacitor' thingy about 'replacing' or 'smoothing' power draws. In the primary power side of it they are a lot more trouble($$) than they are worth.
The point I am trying to make is that they can also be very dangerous in the right/wrong circumstances. One of those circumstances is when you have to 'jump' a battery because it's 'dead'. If that capacitor doesn't have a voltage rating at least 2 - 3 times the voltage normally applied to it you have the definite possibility of 'over-volting' it and that makes for one very large bang. The best way of preventing that is by taking it out of circuit if/when you need to 'jump' a battery, or any instance where you can get a voltage surge/spike. The least of your worries is a fire. The much greater worry is where all that shrapnel goes when it explodes. That's not a joke by the way...
- 'Doc

Oh, and that capacitor doesn't 'save' the alternator any work! It still has to charge or recharge that capacitor. Capacitors only 'store' power for very short period of time (fractions of seconds, not minutes). That 'storage' is what batteries do.

Another "Oh" thingy. That 2 - 3 times normal voltage rating is a very conservative guess. The higher that 'safety margin' the better off you are. A voltage rating in the hundreds is NOT unreasonable in that sort of situation. But it's your neck...

[MDYoungblood]

'Doc always has a good point and I have seen this happen with a CDIS (capacitive discharge ignition system), the poor Mustang had just got a fresh paint job too. Since the alternator does all the work after starting the vehicle my best suggestion is to get an alternator('s) big enough to handle the job or be happy with a smaller amp. JMO.

3's

Greg

[p38]

Ive never had that happen or even heard of it and ive been too many competitions ,im not going to doubt you on it either ive seen batteries let go and it isn't pretty . they do however save the alternator! there entire purpose is too save the alternator on the initial start up of when you key up/or the Audio system hits (amplifier kicks on ) it then slows the rate of which the amp has too work so your not burning out alternators.

['Doc]

Think that through again. That capacitor isn't 'saving' anything unless the alternator isn't capable of sustaining the load to start with, it's too small. The alternator will always have that initial 'surge' or draw to charge the cap, so why not 'fix' the problem where the problem exists?
- 'Doc

[p38]

The purpose of a car audio capacitor is to deliver large amounts of current very quickly faster than a battery is capable of, which means an easier load on the alternator and battery because of so much draw on initial start up of the amp . all a capacitor is ,is a battery that is built and designed too hold power and be ready on demand . a battery cant handle quick discharge very well they do not last long under that kind of abuse even with a deep cell battery . I have dealt with this issue since I started working on cars long before my certifications it got even worse when I got into the rock crawling seen with enough lights to light up foot ball fields too practice before games when we had no lights . the best setup has always been a great battery a step up in cables and sometimes one too two alternators sometimes the same with batteries the only batteries too use is an optima but that's a lot of $$$

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Monday, 11 February 2013, 14:50 PM

doc the reason why I mentioned these in the first way is its a cheap and efficient way too go and no one is busting there knuckles on alternator bolts and spending $$ where its unnecessary. its the green that matters in the end espcially when most of us live pay check to pay check

['Doc]

I'm sorry 'p38', but that just doesn't hold water. That capacitor has to be re-charged every time it supplies any 'additional power'. That means that the alternator is doing that supplying so isn't loafing along at all. It also means that capacitor can't supply any of that 'quick' power until it's changed again. Which still means that depending on how 'talkative' you are, there's a shortage. There's nothing 'free', and a capacitor is never the same as a battery except for fractional seconds between recharges.
Another way of looking at it is that audio is orders of magnitude 'slower' than RF even if they are both AC (different frequencies). A capacitor may have a chance of 'keeping up' with audio, but not with RF in these circumstances.
- 'Doc

[Slyguy]

I'm with Doc on this one. That cap doesn't charge itself. It's not making magic free electricity. Those caps are installed for the most part to prevent voltage drop to the audio amp when the bass hits hard. This would not be an issue if large enough cables were installed to power the amp. this is why these caps are installed at the amp. Their not put there because the battery can't handle large loads, but because the power cables feeding the amp can't.

Now lets get back on topic. The OP didn't ask about installing capacitors. He asked if his idea of installing a second battery was a good one.

[yamaha]

I'm with Doc on this one. That cap doesn't charge itself. It's not making magic free electricity. Those caps are installed for the most part to prevent voltage drop to the audio amp when the bass hits hard. This would not be an issue if large enough cables were installed to power the amp. this is why these caps are installed at the amp. Their not put there because the battery can't handle large loads, but because the power cables feeding the amp can't.

Now lets get back on topic. The OP didn't ask about installing capacitors. He asked if his idea of installing a second battery was a good one.

Exactly, I was In car audio and DBdrag way before I ever keyed a radio,,, Caps Only help maintain voltage during times of high amperage being drawn... They can help to keep everything nice and strong!!

[p38]

whole purpose I brought this up is too save the charging system the initial shock of start up of the amp(key up) meaning the voltage spike as well as sudden spikes in voltage across the board (rms) when audio levels change in music or in your voice ,yes they're installed too prevent a voltage drop resulting in poor audio etc but we also use them too save the life span of the charging system and battery I wasn't looking to get into a huge Debate here thank you yahmaha thats what ive been trying too get at! ohh and Slyguy I have a link that may be useful too a ton of people here might ave some head aches and a few wires too! [Please login or register to view this link]

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Monday, 11 February 2013, 21:35 PM

and on that note AR 228 unless your running some serious power your best route is a great battery (I recommend the optima line its always done me right) good cables and dont cheap out on connections the cheapo's do not last very long but I wouldn't know anything about that .

[Dewey1384]

I'm sorry 'p38', but that just doesn't hold water. That capacitor has to be re-charged every time it supplies any 'additional power'. That means that the alternator is doing that supplying so isn't loafing along at all. It also means that capacitor can't supply any of that 'quick' power until it's changed again. Which still means that depending on how 'talkative' you are, there's a shortage. There's nothing 'free', and a capacitor is never the same as a battery except for fractional seconds between recharges.
Another way of looking at it is that audio is orders of magnitude 'slower' than RF even if they are both AC (different frequencies). A capacitor may have a chance of 'keeping up' with audio, but not with RF in these circumstances.
- 'Doc

Due to battery chemistry, the battery is incapable of providing transient spikes when the current required by some high drain devices (high wattage amplifiers either audio or RF - doesn't matter). Large capacitor can provide the initial current spike and the battery(s) can come on-board later in time. Once the battery chemistry catches up (followed by the alternator circuitry) then the alternator and batteries can replace the charge held by the capacitor(s). Capacitors have 2 general purposes, what I previously mentioned and in the case of filter capacitors to draw down voltage spikes.

[420Snowman]

I use a cap and an optima second battery for my 8 fet and the only difference I notice is the bird meter jumps up a little quicker when I initially key up..... Quicker response time I would say......


Snowman

['Doc]

I have no idea how many times this same topic has come around and I have no intention of going through it again. All that I will say is that you seem to have an incomplete understanding of what and how a capacitor acts and would suggest going over some basics about them.
The one thing that is very important to remember is that the larger they are the more dangerous they are. It isn't a joke/myth about them blowing up and causing damage to their surroundings.
- 'Doc