Adding a second battery

[chandler2572]

Was wondering if anyone can help me.I have a 2.5L V6 calibra and am currently in the process of upratting my sound system.
I have been told to fit a second battery in my boot.This does not seem to much of a problem but I disagree with the advice I was given on fitting it.
I was told it could come direct off my 1st battery(so it would be constantly charged).
Someone else told me there is a 2nd connection off my alternator that I can connect to.This option appears far to difficult as the alternator looks a right b****** to get to!! Can someone please advise the best way to do this! I do have basic electrical knowledge..Thought this would be the best place for advice!!

[davamb]

Don't ever parallel batteries. The terminal voltages are never the same and one will end up hogging the charge.
As for a second terminal on the alternator, I believe the correct slang is "b*******"!

Use a Schottky diode such as the MBR1545CT. This is a dual diode in the one TO-220 pack, rated for a reverse voltage of 45V, at 15A (both diodes in parallel). Connect anode to your main, cathode to you auxilliary battery. Insulate the flange of the diode as it's the common cathode or use this directly connected to the (+) terminal of your aux battery as a heatsink. Connect aux battery (-) to chassis. If your sound system current is greater than 15A, get a higher rated diode.
You should be able to get the diode from Farnell or RS components. Less than $3 Aussie, what's that? 50p?

[chandler2572]

Thanks mate.Decided to go with a split charger kit.It has a split charge relay.With a manual switch over ride.Have not installed yet but has very straight forward instructions..Just hope my mate hurries up in building my BASS bins!!