View Full Version : isolated battery question

07-14-2011, 10:24 AM
In my former boat, I had 2 DieHard Platinum marines hooked up with the Borg Warner Key hot relay - worked great.

My new boat had an Optima to run starting and all electronics, so I bought a Die Hard Marine to do the starting and put the amp on the Optima. I've had better luck out of the Plantinums than the Optimas.

Since these are different types of batteries, I did not hook them together.

I got about 5 hours of stereo time out of the isolated Optima, and then charged for 4 hours last Saturday but the amp started cutting out after just about 30 minutes.

SO, I could spend $300 on another Die Hard Marine and hook them together with a battery switch, but it could be the amp starting to have problems or could be my battery charger used on the Optima is bad.

MY QUESTION, anybody run a pure isolated battery and if so, how much stereo time you get out of it? I wonder if it was just down enough that 4 hours wasn't enough to get it back at operating amperage.

07-14-2011, 11:50 AM
Unless you are perhaps running a jet boat, pontoon, etc, with only light stators there is no reason for total isolation. The isolation only becomes necessary at rest or after a prolonged period at rest. Until that event occurs and the batteries are drained, having a fully charged zillion amp/hour capacity is not a liability to your alternator.
The existing Optima battery that you have may not have been cared for properly...typically they are not. It may be done. A bad battery used past its time is a liability to your charging system. Have it load tested or see how much of its charge it will maintain once fully charged, totally isolated and at rest over a several day period. It might initially charge up to 12.7, 12.8 volts but if after only a few days it drops more than 3 percent without a charger on it, then you have little time left.
A tender/maintainer/trickle charger results in the premature demise of a true deep cycle that is repeatedly deeply discharged.
Also, having too little reserves so that you fully discharge your batteries is destructive even for a deep cycle battery but instantly terminal for a cranking battery.
A yellow, red or blue top with a black case is the wrong battery. It needs to be the Optima blue top with a gray case only.

Earmark Marine

07-14-2011, 12:07 PM
Got it. thanks - think I am just going to put in the Platinum marine and get a cutoff -

07-14-2011, 12:09 PM
If you are looking for an easy battery isolator check out the battery doctor

07-14-2011, 12:50 PM
I have the blue top Optima Marine - former owner bought it - it's just a year old. I guess I am asking if anyone ever runs a battery, not connected in any way to a cranking battery (thus alternator) - for their stereo system. Does a battery that runs a stereo/amp system need to be connected ultimately to the alternator?

07-14-2011, 01:27 PM
ideally if you dont want it to completely deplete which is not suppose to be good for these batteries.

07-14-2011, 01:28 PM
the battery doctor is really easy to install and it works of voltage so you never fully drain a battery (i think)

07-14-2011, 01:37 PM
No it doesn't need to be connected but being isolated all the time will result in deeper cycles which translates to shorter battery life. A deep cycle battery can tolerate an infinite number of shallower cycles versus far fewer deeper cycles. Its far from an equitable ratio. And a totally isolated stereo banks results in an accelerated voltage drop. This means that an unregulated amplifier will lose about 10 percent of its power for every drop of 1 volt. The amplifiers will work harder at low voltage resulting in a higher occurance of thermal issues.
So, if totally isolated you better have a massive battery bank and since you will be 100 percent dependent on shore restoration you better have a mondo charger to combat sulphation.

Earmark Marine

07-14-2011, 02:37 PM
Thanks to ALL!