Another Battery

93_4Banger · Post by **93_4Banger** » June 12th, 2006, 4:06 pm

I was wondering if you can run a battery off the other battery so i can put one in the trunk for a stereo system but without relocateing the other one in other words running two batteries can you do this?

mr1in6billion · Post by **mr1in6billion** » June 12th, 2006, 4:18 pm

ariesdude · Post by **ariesdude** » June 12th, 2006, 5:02 pm

It is definitely possible (with the right wiring) - but -
1) might need higher capacity alternator to keep them both charged
2) the other battery might have to be rigged to cut-off during cranking.
3) even with two batteries it may not solve the light dimming with subs problem - need a cap for that - batteries are good for constant and continuous supply - they wont do much for high frequency surges produced by high power amps.

93_4Banger · Post by **93_4Banger** » June 12th, 2006, 5:35 pm

I just want it to keep the mess out of the engine bay and just power my audio set up. Can you explain the wiring?

ariesdude · Post by **ariesdude** » June 12th, 2006, 6:17 pm

What is the power requirement of your amp? If its just something like 30 amps peak you dont need another battery - you just need to run a 4 or 6 gauge wire from the battery to the amp - add a capacitor and you should not have light dimming problems for the most part.
If you go for a separate battery you still need to run that wire from the first battery anyway (to charge the second one)- but in this case either you need a much bigger wire (like 0 gauge) or you need a way to cut out the second battery during cranking. cranking takes a much higher current (300+ amps) and if that much current happens to run through normal 6 gauge wire you might be wise to have a fire extinguisher nearby.
There are lot of people that have relocated their battery to the trunk. What you are thinking about is much similar in terms of procedure and materials except you are not removing the battery from the bay.

mr1in6billion · Post by **mr1in6billion** » June 12th, 2006, 6:22 pm

ariesdude wrote:It is definitely possible (with the right wiring) - but -
1) might need higher capacity alternator to keep them both charged
2) the other battery might have to be rigged to cut-off during cranking.
3) even with two batteries it may not solve the light dimming with subs problem - need a cap for that - batteries are good for constant and continuous supply - they wont do much for high frequency surges produced by high power amps.

1) Putting two batteries in parralel just increases the total capacity of charge your system has so you won't need a better alternator, but given the crappyness of our alternators it's probably a good idea.
2) You don't need a cut off for cranks, but generally you use an isolater for one of the batteries.
3) yup

I just want it to keep the mess out of the engine bay and just power my audio set up. Can you explain the wiring?

Large gauge wire from one positive terminal to the other positive terminal. The wire needs to be fused at both ends. The battery in the trunk is just grounded to the chasis. If you want you can use an isolater on the front battery, that way your sound system will only run off the trunk battery; that way if you are playing music with the car off, your rear may drain, but the front will still be able to crank the engine.

93_4Banger · Post by **93_4Banger** » June 13th, 2006, 12:30 am

Just wondering where i could possibly purchase a isolator and thanx guys thats all i wanted to know

Nd4SpdSe · Post by **Nd4SpdSe** » June 13th, 2006, 4:22 pm

I have 2 batteries, 2 optima red tops in parallel (no isolator), been running like that for 2 years. The second battery is in the trunk, ran from the front battery terminal using a 0 guage wire, fused a few inches from the front battery terminal only.

Having 2 parallel would actually double the cranking amp capability, so I don't see the reason (or ever have i heard or anyone suggested) a crank-cut off system, unless maybe your using sub-par wiring to the second battery.

Battery or cap, it's just a band-aid solution to another problem, alternator or wiring/ground.

1) Putting two batteries in parralel just increases the total capacity of charge your system has so you won't need a better alternator, but given the crappyness of our alternators it's probably a good idea.

Exaclty. It's really no extra drain unless both batteries are dead, but even then, the same charge given by the alternator will be split between both batteries, although you'll have less voltage, you'll have the same amout of amps. If both batteries are half-charged, it's still the same power-reserve as a single battery. It should be easier on the alternator since there's more stored charge. Even looking at it another perspective, if the alternator decided to charge when it drops below a certain voltage point, it'll take half as long to get there because you have 2 batteries to hold the charge, but will take twice as long to return them to it's recommended voltage. It takes twice as long to charge, but kicks in half as much, the same thing in the end really, but alternators are designed to run at 100% duty cycle.

Runing 2 batteries in parallel, they need to be of the same type, model and age. The isolator allowed you to mix-match, you can also run the rear battery dead, and it will not affect the front battery, and allow you to easilly start your car. If you want to so that, definitely run a deep-cycle as the second battery. I've normally known isolators for use for camping trailors. You can probably find it in the electrical section of the towing accessories.

reaper of souls · Post by **reaper of souls** » June 19th, 2006, 4:35 pm

you say that you just want to run it for your audio and don't want the mess in the engine bay

1) learn to run wires properly and there will be no mess

2) you still have to run new wires in the engine bay to the other battery (if not larger awg wire then would be needed for your system to run)

if you don't want the mess or want your power wires visable (which sounds more understandable) get your self some split looming and some zip ties and just route your power wires along the same path as other wires ( you'll get a factory installed look if done with a little patience)

i think your asking for more of a hassle than is needed. save the hassle get a cap, a distrubution block some 4awg wire and some 8 awg wire.

this should be enough, run the 4awg to a distro block then from the block 8awg to the cap and then to your amp. ground the amp and the cap. this way if you have another amp or are looking into two amps you can run the second off the distro block this way everything stays nice and neat ( also you can run and hide all the wires and distro blocks under the rear seats mount cap and amps to the back of the seat and run the wires up to the amps and such under the carpet on the rear of the seat.

Reaper

WingleBeast · Post by **WingleBeast** » July 25th, 2006, 8:27 am

where could you find an isolator for that kinda of application?

Cy · Post by Cy » July 25th, 2006, 11:53 am

can-tire sells isolators...or most good car audio shops...

I didn't use an isolator.. i just use 2AWG wire from the Side positive terminal of my front battery through the firewall, next to the muffler tunnel under the back seat to the back corner of the passenger side-trunk.. Battery is secured to the trunk with a rubber strap... and a Ground strap...

I have upwards of 1200CCA..and @ the drive-in last month my 200W HU+300W Amp didn't drop below 13V after F&F3...then i ran the car while i got more Snax...

C-tire online lists a 85 and 95 Amp isolator

WingleBeast · Post by **WingleBeast** » July 25th, 2006, 3:57 pm

well in the futurei plan on running alot of car entertainment and lighs and so forth, and i rather have that hooked up to a seperate battery, and leave my main battery for the stock stuff plus my ignition controls, air fuel controls, nitrous... all that good stuff

Cy · Post by Cy » July 25th, 2006, 7:08 pm

buy 3 of the same battery and an isolator...

3 optima yellow tops with 2 in a bank on he isolator and 1 in the engine bay would be like 3hrs @ the drive-in with a 1000watt stereo...and never having to run the engine