I am aware of all of that. But, bridging two batteries, especially the way I have done it, will basically give you exactly the same power for longer. I barely ever run my stereo when my car is stationary therefore I did not need the isolator as my stereo was going to be off whenever my car was off. The main two reasons I added a rear mounted battery was because,
a) Made it a lot easier to connect amps directly to battery rather than to a distribution block.
b) Has completely stopped my headlights from dimming when the bass hits hard as there is a lot less current draw on my main battery.

The idea of having two batteries is NOT just so if you run your stereo for a few hours and drain the battery, there is still another one to start your engine. Otherwise they would not put more than one battery in a TV remote. Think about it. My two batteries are the same capacity and brand and therefore will perform the tasks I want them to.

ok.
I agree it will fill your requirements perfectly.

PS. there's 2 batteries in a tv remote because they need 3 volts. 2 x 1.5v battery.

touche'

lol chillout dude .. the ol maximus hehe sorry dude has been round this forum for yonks helpin ppl out so before pullin smart a*** touche comments have a read of your own the last statement you posted in the above was pretty arrogant dont u think ... anyways ... Just cause your car is off or the sound system is off is irrespective of whether or not your battery/batteries can be drained...its happened to many before....my car security system will do it if the car isnt started for 2-3weeks because of data logging.... Isolators are a cost effective way to protect electrical circuits, make disconnecting the power in emergency situations less dangerous etc etc ... yes how u will have it setup will do the job...effectively doubling your reserve capacity.

By the way what output ratings have u got for those batteries...there mighty small/thin

Another thing too note ... this setup 'may' have also not fixed the issue you are having with headlight dimming mearly masked it or made the cause of voltage loss less aparent...reason i mention this is too why i was asking bout your battery specs regardless that u have two....

Yeh... he caught me on a bad day. Apologies. They are piss small batteries. Only a 40ah Supercrap (they were having a sale ) battery in the rear and I dunno what's in the front. Now I've had a bit more advice, I've realised the way I've got it at the moment is s**t so it's all getting re-done next school holidays. My life is full of quick fixes when it comes to my car as I always end up running out of time to finish the job properly. Damn school. I'm going to chuck a pair of matching 70ah batteries in and re-do my alternator wiring and battery to battery wiring with 10mm housing wiring.

Once again. Sorry to Maximus for the arrogant remarks and all that. Year 12 can make the worst come out in me.

house wire is 2 small and once u get to decent sizes hard to work with. go welding cable (flex) if u arn't going to use proper cable.

2 battries unless indetical will have different impedence and hence one will act as a small load on the other.

get old of a battery impedence meter if u can.

Thanks for the info but I already knew all that thus I am getting two idectical 70ah batteries. This is only a very temporary setup. By saying 10mm housing wire I kinda' meant welding cable. I'm not a sparky, my dad is, so I just call it housing wire. 10mm welding cable is the equivilent of 000g audio cable so it's more than thick enough. Learning every day I am. This thread was started a while ago and I've learnt a lot since I asked the question. I don't really need an answer anymore

How's your pick?