Non-matching 2nd battery

I got my hands on an Optima battery that I thought about mounting in my trunk and running my stereo off of. Upgrades coming are 200 amp alternator and upsizing the big 3. I'm leaving the stock battery as it is to use for starting then only the stereo will run off the new battery. I plan to run 1/0 from alternator to trunk bat +, 1/0 bat negative to chassis ground, and run the grounds from 2 amps to distribution block then directly to battery.
Is this setup ok? Do I need an isolator? If so, how is that hooked up? Any help is greatly appreciated.     

i do not recomond useing mismatched batt. end of story.

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To prevent charging problems when connecting batteries in series or series-parallel, do not mix old and new batteries, ones of different capacities or types. Mixing old batteries with new batteries is like mixing old milk with new milk--soon you have nothing but old milk. The weakest or smallest capacity battery connected in series or series-parallel will over discharge and overcharge, which will eventually cause a premature failure.

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First of all, thanks for the responses. So what you're saying is I would be running them in parallel because the positive wires would be connected at the alternator?

With my old stock battery I couldn't play the stereo with the engine off for more than 5 minutes before the engine had a tougher time turning over. I don't listen with the engine off very much, just when I want to do some tweaking and don't want to use any gas. Both batteries are new so, I think that I will try my luck and use both.

nouseforaname wrote:

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now i agree don't mix old and new batterys. but as far as types, i've never had a problem nor has all the people i know thats doing the same thing. guess we're all really lucky.

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lets put it like this would you run 4awg power wire from batt. to amp only to use 10 awg ground? why not i will work. heres why , that small ground wire we all know can rob of any where from .5 volts on up.

so my questionis is , why would you use a batt. set up that can do the same after all we are adding second batt. to get more power right?

yes i know many people that have odd batt. setups and their cars dont expload or any thing bad, but is it best when 1volt can mean the difference between your 1000w rms amp only doing 800w rms?

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I have a similar problem as djsae.  My car has 2 1250w amps and 1 800w amp powering 4 subwoofers and my componet speakers.  The thing is, everything is running off of the main battery, and I do not know how to install another battery to run everything off of.  So if someone could tell me what it is that i need to do, that would be wounderful.

Here is a past thread with haemphyst's argument about connecting dual battery setups:  Best Way to hook up Dual Batteries?  More threads can be found by using the Google "current site" search for "battery", or the forum search icon atop this page.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

im going to quote haemphyst from the link above.   "as an electrician with 6 years in the field, and a military electronics background, simply wire them in parallel. Alternator to front battery positive to back battery positive, then run your distribution block right from the rear battery's positive post. Isolators, solenoids, and all of those items are a waste of time if you have an alternator capable of charging two batteries in parallel (and 200 amps will do just fine) Those items will offer you safety when it comes to having to start your car, because only one battery will go dead, but then your system could still starve due to lack of current, and your system will gain absolutely nothing by having a second battery... Make certain you have cable enough to handle the current capacity of your alternator (200 amps, I recommend nothing smaller than a number 2, and make certain you use the same gauge for both batteries ground wires, as well.) and make certain you have TWO fuses between the batteries, one at each end, and each within 18 inches of the positive posts. This is to protect the CAR, not the batteries, do NOT skip this step. Additionally, the batteries MUST be the same type, manufacturer, CCA's, and AMP-HOUR rating, and should be within 3-6 months of age of each other. "


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yes, but all im getting at is i dont like to recomond some thing  based on luck if some one askes me how to do it, i going to tell them the right and best way to do it. not way you can get luckey with, even if lucky means 99% of the time. what if this guy has just the right combo of battries and thay catch fire now its my fault. is it going to happen probley not, can it happen yes.

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yes good topic thanks for all input hope we all have learnd some thing new. i know i did.

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bring back the rotary phone so i dont have to press 1 to proceed in english