hi,

i have got a DVD system in my car and running 2 amps with a 12" sub. i regularly watch movies in the back seat of the car with the engine switched off.

i get really worried that after the end of a 2hr movie, that battery might get drained. So i want to install a second battery in the boot.

But, i dont know:
-how it will work
-what is required
-parts required
-any tips ??

cheers

I am using a stinger battery isolator for my setup. Positive from the alternator goes to the isolator and also a positive from each battery. This in turn distributes the alternator charge to which ever battery needs it. The isolator was about $200 for mine, but i'm sure their would be some cheaper systems you can setup. My advice would be to either go to a specialist car audio store or a a specialist 4x4 store as they will recommend what you will need to use for your needs...

Simple thing to remember about batteries is the following: if you want voltage then wire up the batteries in series. So two batteries in series will get you 24v. This is good for trucks.
But if you want current then you need to wire up two batteries in parrallel to get current. Positive battery terminal to positive battery terminal and negative battery terminal to negative battery terminal. Then you will have double the current for your car applications.
Alternatively and more cheaply, just get one of those Optima heavy duty batteries that many folks here are running in their cars for all their audio gear. More expensive than a regular battery but they are designed for it and last longer.

DONT wire up you batteries as a 24V system. You will blow everything sky high. DONT DO IT!!!

Sorry, I should have pointed out that 24v is of course not for cars. It was merely an example of series vs. parrallel principles.

heyo,

Jaycar sells a kit for running 2 batteries, i think its around the $50. But if you dont feel like burning your fingers soldering tiny electronic components, then you could goto a 4x4 shop (as Rmyers said) as they have them for ppl who go camping.

Probably the cheapest and easiset solution:

Setup 2nd battery in boot and have your audio/DVD gear running of it. Then have a relay switching + on the main battery to the + on the 2nd battery. THis relay is controlled by your ignition. (relay on, when ignition is on, relay off, when in acesssories is on)

This way when you are driving the alternator is charging both batteries and when you switch off engine just your 2nd batt is running your audio.

a standard large (400+ cca) battery will do as your 2nd battery, i probablly wouldn't fuss with getting a deep cycle or anything special.

cya
Rene.

okay thanx, i have descided to check ebay and found the following isolators, the vary in price greatly.

what are their differences???

are they suitable.

check it out.

hella item ($20)
http://cgi.ebay.com.au/Battery-Isolator ... dZViewItem

$75 item
http://cgi.ebay.com.au/ws/eBayISAPI.dll ... _Stores_IT


$20 item (weird looking soleniod)
http://cgi.ebay.com.au/DUAL-BATTERY-ISO ... dZViewItem


$100 Redarc
http://cgi.ebay.com.au/REDARC-DUAL-BATT ... dZViewItem

http://www.piranhaoffroad.com.au/produc ... ummary.htm


that might help explain some different types

I've got a July05 BA Mk2 XR8 Ute. I've just installed a dual battery system. The second battery is a deep cycle unit, installed in the rear tub which runs the fridge, 3 radio's, tray lighting and phone. I've installed an electronic isolator near the main battery and ran 12mm cable in conduit along the chassis rails to the aux battery in the tub. Turned out to be an expensive exercise, but the aim was to keep cans cold for days on end without flattening the main battery all the time!!