Do I need a bigger battery or alternator?

Dr. Bogger · Post by **Dr. Bogger** » Sat Jan 21, 2012 7:15 pm

I have another question... If I were to keep the stock battery, and add a second battery in the trunk next to the amps & subs... Would I still need to run 1/0 AWG wire to the stock battery, or could I get away with using 4 AWG?

My total RMS Wattage is 1400 Watts RMS (using two different amps)
Total fuse rating is 190 Amps (Adding the fuses on the amps to get this number)

My theory is that if I add a second battery and keep my stock battery, I assume it would be safe to use a small gauge wire from the rear battery, to the stock battery, because if i'm correct, it would be used mainly for charging the rear battery, and not used for current draw from the amps...

Do you think I could safely do this?

Bwcad1 · Post by **Bwcad1** » Sun Jan 22, 2012 8:12 am

No. You still need to run 1/0 of all the things to try and save money on wire is not one of them. Your safety and your car are your priority and skimping on the wrong size wire will end up in a fire. Would you be ok with 4ga? Meh maybe but are you willing to risk your safety and your car for 25-50 bucks?

Dr. Bogger · Post by **Dr. Bogger** » Sun Jan 22, 2012 9:50 am

Yeah, I was just curious how that worked... I wasn't totally sure cuz it's gonna be a battery add-on, and the only thing it will be using the front battery/alt for is charging... atleast that's my knowledge... But I guess I'm wrong.. lol

Purple RS · Post by **Purple RS** » Sun Jan 22, 2012 12:26 pm

I can't vouch for how well they work, but the concept is good. These guys have products to combine batteries for starting, yet isolate the backup battery when under normal use. A few different types of products, even a couple for high power audio, which I linked below.

http://www.hellroaring.com/audio.php

Bwcad1 · Post by **Bwcad1** » Sun Jan 22, 2012 5:29 pm

Dr. Bogger wrote:Yeah, I was just curious how that worked... I wasn't totally sure cuz it's gonna be a battery add-on, and the only thing it will be using the front battery/alt for is charging... atleast that's my knowledge... But I guess I'm wrong.. lol

Your not necessarily wrong but remember if you pull max power from you rear battery that rear battery will need to charge at the same rate you discharge so if you do pull 190 amps your rear battery will charge at the highest current it can so it in theory could pull that same amount of current. Thus you need the larger wire to support that. What is the distance of the wire from the front battery to the rear battery ruffly?

Dr. Bogger · Post by **Dr. Bogger** » Sun Jan 22, 2012 6:19 pm

I'd say about 14 feet.

Plus, my alternator is only 80 amps (stock alt).

JeremyC · Post by **JeremyC** » Sun Jan 22, 2012 8:51 pm

How does it work...

Your alternator puts out 13.5 to 14.5 volts.

A standard car battery is around 12 to 12.5 volts.

When the car is running, the alternator is the higher output sorce, so it runs everything, and your bateries set as a backup.

Once the current draw surpasses the output of the alternator, the batteries step in and suplament the diffrence.

Dr. Bogger · Post by **Dr. Bogger** » Sun Jan 22, 2012 9:06 pm

My alt can only output 80 amps... So anything above 80 amps, the battery will supply the rest of the power... right?

If so, My Alt is 80 amps, and 4 AWG wire can handle 150 amps...

So I should be able to run 4 AWG wire from the rear battery to the front battery (Cuz the current will only be about 80 amps), and then 3 feet of 4 AWG wire from the rear battery, to the amps. (3 feet of 4 AWG wire can handle over 500 amps)

Again, I could be totally wrong here... This is just what makes the most sense to me...

Bwcad1 · Post by **Bwcad1** » Mon Jan 23, 2012 5:03 am

Your front battery can also charge your rear battery that's what your both missing.

Bwcad1 · Post by **Bwcad1** » Mon Jan 23, 2012 5:04 am

Battery's like to stay even with the same amount of charge so if your rear battery discharges by 200 amps the front battery and alt will try to supply 200 amps to charge it back up almost instanteously hence the need for larger wire. If your dead set on saving 50 bucks on 4ga go for it but you are compromising your safety