I need straight info on extra battery install.

[Bushmaster]

Hello...

I'm going to post this question in several catagories so that I can get the best number of responses possible.

Here's my specific situation:

I have a '96 Nissan Sentra with a stock 75 amp alternator. I'm presently geting ready to install a Cobra XL-450 amplifier to run behind my Lincoln radio. The amp pulls 40 amps.

In the past, I have fried several alternators after a couple of years of regular use of smaller amps (also in Nissan Sentras), albeit older models. I'd like a bulletproof setup, even if it is slightly overkill, because I don't want any additional headaches in the future. If the smaller amps eventually toasted the alternator, this one probably will too. What I'd like is some more capacity.

I need to know if adding a second battery in the trunk is the best way to go, short of adding a bigger alternator. If so, how EXACTLY do I wire this system? Do I merely run a heavy cable from the positive battery post on the battery in the engine compartment to the positive battery post on the battery in the rear? And then run a short heavy cable from the negative post (on the trunk battery) to the nearest ground in the trunk?

If so, I assume that I then simply run an adequately sized set of power leads from the trunk battery to the amplifier. Correct?

Also, would it behoove me to piggy back the power lead coming from my positive output on my alternator to the positve terminal on the original (engine compartment) battery? And then also piggy back the negative terminal from the alternator to the nearest ground? Any special considerations here?

Which would be the cheaper way to go? Extra battery (and related accessories), or bigger alternator?
Which way is the best?

Thanks for any help you can offer. Please give the most thoughtful advice you can, because I'll be using it!

 

[2M Guy]

Isolate the second battery with a constant duty solenoid. They are 20-25$ at a parts store.
Just hooking two batteries can leave you stranded. One will have slightly higher voltage. The weak battery will drain the stronger, until it becomes the weaker. Then back and forth until both are drained.

 

[billy the kid]

if it just pulls 40 amps i would just put a 150 or 250 amp altornator on the car and run #8 or less from the bat to the box and a #8 or #10 strait from the alt to the bat it helps 73's god bless

 

[KingCobra_CDX882]

billy the kid got it right
bigger alt far better

 

[995]

billy the kid got it right
bigger alt far better

I agree on the bigger alternator, but not on the #8 or #10 wire from the alternator to the battery.....

 

[Switch Kit]

COBRA XL 450 ? 75 amp alt ? Thats' more then enough to run 4 x 2290s/454s , IM sorry that IM about 8 months late on this thread , but i run the same amp on a 65 amp alt with a 29.99 Walmart battery for the last 2 years without a problem in the world. No I don't run my air conditioner at the same time , but at night with my running lights , have no problems at all , maybe if IM stopped at a light and i key up , if you look very closely you might see a flicker of slight dimness ,other then that , I've had no problems what so ever. 40 amp draw on these huh , I'd really be surprised if that were true . These are nice amps and the last thing I would want to do is screw it up . I give it all it needs. Mans got to know his limitations , but I will agree , nothing wrong with pumping the power up to be on the safer side of things. IM not going there.

 

[hotrod]

if it just pulls 40 amps i would just put a 150 or 250 amp altornator on the car and run #8 or less from the bat to the box and a #8 or #10 strait from the alt to the bat it helps 73's god bless

i agree with billy the kid.2 batteries are more trouble then its really worth imho

 

[KC2OST]

if it just pulls 40 amps i would just put a 150 or 250 amp altornator on the car and run #8 or less from the bat to the box and a #8 or #10 strait from the alt to the bat it helps 73's god bless

i agree with billy the kid.2 batteries are more trouble then its really worth imho

Plus you are stealing more power to charge the extra battery.
So you have less power for your amp and vehicle.