Whacky but useful idea ?

[loanrangie]

I am installing my GME TX3400 in my Disco as well as fitting a dual batt system and i had this idea of somehow making a small electronic controller that senses when there is no power from the 2nd batt (if removed ).
Basically so i would have power from the igniton circuit and the 2nd batt connected to this device so that if for whatever reason i dont have a 2nd batt in place, this controller could sense it and switch to the main batt via the igniton circuit. Is this do'able or am i just dreaming ? This would allow you to use any powered items that normally hook up to the main power but when the ignition is off can still be powered by the 2nd batt and vice versa ?

[waynep]

I would have thought Drivesafe's SC40 would do that anyway. If you just connected it as normal, then removed the second battery for some reason, as long as there was a circuit still through to the accessories the SC40 would still pass current until the voltage in the main battery got to below 12.5V then it would automatically disconnect.

Better let Drivesafe confirm that though.

[loanrangie]

I would have thought Drivesafe's SC40 would do that anyway. If you just connected it as normal, then removed the second battery for some reason, as long as there was a circuit still through to the accessories the SC40 would still pass current until the voltage in the main battery got to below 12.5V then it would automatically disconnect.

Better let Drivesafe confirm that though.

Yeah but what i am getting at is if you had say your stereo wired in a way that it would have power from the normal ignition source as well as from the 2nd batt, when no power is sensed from the main, power would automatically be switched to come from the 2nd batt so that you could run the stereo off the main as usual untill the ignition is completely off and it would then revert to aux power ?

[waynep]

Yeah but what i am getting at is if you had say your stereo wired in a way that it would have power from the normal ignition source as well as from the 2nd batt, when no power is sensed from the main, power would automatically be switched to come from the 2nd batt so that you could run the stereo off the main as usual untill the ignition is completely off and it would then revert to aux power ?

Ohhhhhhkaaaaaay ........ sort of lost you now but as a mate used to say anything is possible with relays !!! :D

[cookiesa]

Can't see any advantage in what you want to do (I may be missing something... about the thread!)

You could end up flattening your main battery this way so effectively you may as well do away with dual battery controller and just wire them together to give you greater capacity.

Why not just rewire so the main power for your stero etc runs to the auxillary battery?

You mention wanting to be able to run it "without" the second battery, as long as they are wired to the + terminal along with your controller, and your controller doesn't need a voltage sensing wire from your auxillary, and you have all this well insulated it would work. (This is effectively what happens anyway, the battery is only for storage )

But again not sure why?