Battery isolators....

[cjj2d 10+ year member]

I will be installing a second battery most likely, and is an isolator necassary??

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[Alexwaves 10+ year member]

dont use a isolator use a soloide (i can never spell it)

the reason is that a battery isolator is basicly 2 huge diodes and each time you pass voltage thru a diodes you will lose .7volts and the battery isolator has 2 of them so you will lose 1.4 volts which could mean that your amp(s) will not perform 100% most amps do best at 14.4 so if you lost 1.4 from 14.4 thats 13.0 that you are left with and that could mean a 100 or more watts lost.. now the soloide is pretty much a huge relay so there for there is no voltage lost

 

[yacob.naif 10+ year member]

And to answer your question, isolating two batteries is for operating your system with the ignition off, keeping current draw restricted to the battery designated for your system, and keeping your starter battery safe.

So it depends on your application. Both batteries will charge regardless, despite what some people believe, you just need one for 12v use.

 

[headless 10+ year member]

I wouldn't (And didn't in my car) bother unless you intend to run your stereo for extended periods of times without your alternator charging your batteries (ie. engine off.)

 

[helotaxi 5,000+ posts]

A solenoid will do the job and for less money. If you aren't running the system with the engine off and the batteries are the same make/model, it isn't needed.

 

[nVRuckus 5,000+ posts]

A solenoid will do the job and for less money. If you aren't running the system with the engine off and the batteries are the same make/model, it isn't needed.

what if you have a stock battery under the hood and a yellowtop in the trunk. Do you need a solenoid? car will alway be running when audio is playing.

 

[cjj2d 10+ year member]

thanks, I didn't think I needed one.

I don't play my stereo without my car running, so no need for one here.

 

[iceteebone 5,000+ posts]

what if you have a stock battery under the hood and a yellowtop in the trunk. Do you need a solenoid? car will alway be running when audio is playing.

i heard that when 2 batteries are wired together, they could actually drain each other, so that's why people use a relay or solenoid or get 2 of the exact same batteries

 

[helotaxi 5,000+ posts]

what if you have a stock battery under the hood and a yellowtop in the trunk. Do you need a solenoid? car will alway be running when audio is playing.

That is where an isolator comes in. The two batteries will interact. Not a huge deal with the car running, but as soon as the car is turned off they will attempt to equalize each other. If there is even the slightest difference between the voltage on the two batteries or their ISR, they will go back and forth with each other and one or the other will usually end up dead.

If you plan on running two different batteries and don't want to end up with one or both of them dead sooner than they should be, get an isolator. An isolator is better for this than a solenoid because it isolates the batteries from each other with the car on or off. No interaction. The stereo will only tap into one of the batteries when it needs current (protecting your starting battery from being drained and damaged) and still allows the alt to charge both batteries. A solenoid will do the job with the car off but not with it on. As far as voltage drop goes, you will only lose the voltage once (.7V assuming a standard silicon diode, only .3V for Germanium or Schotky diodes) because each battery has its own diode and they are wired in parallel. Only one diode on each lobe of the parallel circuit so you only have the loss once. If you are really worried about it and are running an unregulated amp in competition and need that extra .3-.7V get a hot alternator (more than 14.4V) to account for the drop. If you are competing this is really all moot though since you are probably running a huge battery bank and they are all the same. If you aren't competing it won't matter.

 

[Chriscivic 10+ year member]

how does an isolator allow both batterys to charge from the alt. but not connect to each other? how are they wired, i have a regular battery up front and want a second battery(optima, kinetik,etc, some deep cycle) to put in the trunk. anyone haev a link to a diagram,etc.

Thanks,

Chris

 

[nVRuckus 5,000+ posts]

is the isolator needed even if they are both running from the alt and not battery to battery?

 

[Blunt 10+ year member]

is the isolator needed even if they are both running from the alt and not battery to battery?

yes because they will still be connected to each other at the alt

 

[helotaxi 5,000+ posts]

The isolator as mentioned earlier is two diodes, one for each battery. A cable runs from the alt to the isolator and then each battery has its own diode and output pole. Think ofa diode as a oneway check valve. Current can only flow one way through it. That one way is from the alt to the battery. Current can't flow from the batteries to the alt or from battery to battery. You connect audio system at the second battery. The starting battery is completely isolated from the audio system and the batteries dont mess with each other.

 

[RFCV 10+ year member]

Check this out:

http://www.bcae1.com/battiso.htm

 

[SPL140.2 5,000+ posts]

If your running an spl setup my opinion is NO dont do it i think it was mentioned above by ill say it again youll lose voltage.