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Hey guys. I'm getting my alternator souped up to a 200amp. Also I'm gonna run a red top optima in the trunk. Where can i get a 12volt isolator for cheap? I got a quote of $125 at the rebuild shop. Thanks
 
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Not sure what you are trying to do. I'll try to keep it simple by asking you when the last time you saw a multiple battery w/ isolator set up in a car. Maybe there are some out there but there are better ways of doing what it is I think you are trying to accomplish. The alternator upgrade is a good start if you really need it. Adding a 2nd battery is a waste unless you are just wanting to be able to listen to listen to the tunes w/ the car off for a long time.

I'd make sure you current battery is in good shape (replace it w/ the red top if you are worried about it) and use a cap(s) installed as close to your amps as possible.

The problem w/ isolators is you will always have a voltage loss through them and reliability can be an issue. The less you spend on one, the more likely you are to run into these shortcomings.

HTH

Aaron D
 
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Discussion Starter #3
not true...

i had an isolator in my car for over 4 years with a single yellow top in the trunk. never had a problem keeping it charged (stock 60A, amplifier power anywhere from 800W to 2400W, depending on which install hehe)...never had a problem starting my car...voltage drop was severe at the high power range but that's expected with that size alt


isolators generally do have a voltage drop across them. Some isolators are simply massive diodes, others are more complex...either configuration will create resistance in the path which effectively decreases voltage. I think i read somewhere that average loss is around 0.7V which would be what my Electronics II book said as well (ideal voltage loss across diode). The isolator keeps the stereo from pulling current off the stock battery...regardless of if the key is on or off (it was on mine i know).

key here is to run a large enough gauge wire to the secondary battery so that current flow is not restricted. also, be sure to wire your amps up to the secondary battery and not the stock. Cd player and other signal processors should be fine on the stock since they draw low current.

also, caps should generally be avoided until you have your battery voltage under control by upgrading the alternator. Problem with caps is that on bass heavy music, if your alternator can't supply your amps with enough juice the cap helps keep the voltage constant. That's fine and good IF your alternator can keep up. However, if yuo're already losing voltage that means the alternator is too small to run your amps. The cap will discharge before the alt can recharge it and repeats until the cap has quickly become an ADDITIONAL load on the alternator.

This is exactly why you never see SPL competitors using caps (might see a few 50-100F caps, but that's a different beast ;) )...the caps drain completely in the first quarter second or less of the bass tone, alt is tryin to run the amps, cap becomes drained and needs recharging, losing power to the cap. But the cap can't recharge because the music is still playing...robbing your amps of current that could have been being supplied by the alternator :(

wonder if that makes sense...3AM, final design project due monday, lack of sleep all week, lack of food...hope graduation's worth it lol
 
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Thanks for the advice Aaron And Elemental. I have a red top already and getting another one for the trunk. The isolator I'm refering to is a battery isolator with a wire hooked up to ignition to come on when I start the car. The isolator will charge both batteries, but the power from the trunk battery will not back feed into the hood battery. Also I've tried caps, and in 110 deg vegas weather with the A/C blowing at a stop light, my voltage gauge always sags to the low line. Oh well, it's better to do it right the second time around. Especially with 2000 watts blowing up the block. I get my souped up alternator soon, I'll let yall know how it does. Peace outside
 
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btw...if you haven't bought the red top already DON'T! if you have, see if you can return it or exchange it for a yellow-top.

the red tops are meant to be used as regular starting batteries. and like a regular starting battery, if you kill them once you can severely damage the lifespan/charge of the battery. Also, optima's warranty doesn't cover problems associated with high power stereos...

get the yellow top as it's a deep cycle and meant to be discharged hundreds of times with no damage. I had my yellow-top in my trunk for about 4 years...no problems
you can start your vehicle with them too even tho it's not it's true application.

the Blue Tops are the marine batts (gel cells)...kind of a cross between deep cycle and starting. Friend had 8 of these and 8 RF bd1500's...they did fine at supplying his amps with juice too.

but avoid the redtop for stereo purposes...you'll be better off in the long run
 
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Thanks Elemental ;) . I haven't bought it yet. Still waiting on my alternator. But I'm getting the yellow now. Peace outside
 
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