Batt. Isolator

[loud1988honda 10+ year member]

Do I need a Battery Isolator if im running a Wal-Mart batt. under the hood and a Kinetik HC2400 in the back? Its going in a 88 Crx. Or will it be okay?

Thanks

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[PhatTonyDeMarco 5,000+ posts]

People say its a good idea, just in case, but I am running a wet cell up front and a dry cell in the back without any problems as of yet.

 

[OhioRed 10+ year member]

The reason for having a battery isolator is so that your system will **** power only from the secondary battery when the car is off, so both of your batts wont be ran down and your car fail to start. When the car is started, its started off the primary battery, once the car is running , both of the batteries are in the loop, neither is isolated, so your system draws power from both and the alternator charges both. So when the car is turned off, the secondary battery goes back to being isolated, only the secondary battery will be powering your system, and the primary batt is left alone so it can save its power for starts. When the isolator is used and the car is off, the primary batt is used only for starting, the secondary batt is only used for stereo power. Once the car is on and running, both batts are being used and charged. I know i repeated myself alot there, just wanted to be clear. You can get by perfectly fine without an isolator, just as long as you dont run down your primary batt low enough for your car not to start. An isolator is just used to insure your primary batt isnt drained when the car is off.

Hope that helps.

 

[yacob.naif 10+ year member]

i think it's more an issue of when you want both batteries to charge with the ignition on, which they are already doing now, but isolating your starter battery with the ignition off, so your accessories will only draw from the second battery.

If you want a cheaper solution, you can get a low-voltage interrupt that will stop current from your starter battery to your system if the voltage drops to a set level. They're much cheaper than a high-amperage isolator.

Any kind of switch between your alternator, and your second battery/your system, is going to lose some power along the way, tho. If you don't run your system with the car off, i would do without either.

edit: beat me to it

 

[QtrHorse 10+ year member]

The cheapest solotion would be to use a solenoid. You actually lose a little voltage when using a isolator. You can use a key on power source to activate the solenoid and when the key is out and the radio is playing, it will only draw power from the secondary battery.

 

[johnecon2001 5,000+ posts]

Any kind of switch between your alternator, and your second battery/your system, is going to lose some power along the way, tho. If you don't run your system with the car off, i would do without either.

You forgot to mention its a pretty small amount (if any) that you will lose. And unless you're competing with this system were EVERY volt counts, it's not a big deal. I run an iso, both my batts are the same, but I would hate to drain my starting batt.

 

[loud1988honda 10+ year member]

"Note" this is my daily driver. I won't be playing my system with the car off. So I believe I should be fine.

Thanks

 

[helotaxi 5,000+ posts]

There are two reasons to isolate your batteries. One as mentioned above is to keep the starter battery from being drained while the car is off possibly leaving you unable to start the car.

The other reason is to prevent the batteries from interacting and trying to balance charge between them with the car on or off. If the batteries are of a different type or different age, they will have a different static voltage. With the car off, the battery with the higher static voltage will discharge into the battery with the lower voltage. Over time this can kill one or both batteries.

With a solenoid, the batteries are isolated with the car off, but will still interact with the car on. This usually isn't a problem. With a diode isolator, the batteries are totally isolated from each other. The system battery is the only one that is doing anything for the system and the underhood battery is basically idle. The alt can charge both of them but no current can flow between them with the car on or off.