second battery in boot

[jasonpi]

hi all right im quite a dab hand at installing ice but i am for the first time going to put a second battery in the boot for power straight to the amps, im getting.im undecided but probably go down the audiobahn route again.
so my question would be this what way to go?? altenator straight to second battery or what...never done this and would prefere to go down that route all help would be appreciated.

[diagnosis-dub]

If you gonna install a second battery then the easiest way to charge it is to install a split charge relay.

You can buy a split charge relay kit from most camping suppliers (just Kampers do a bosch one) as its a common upgrade on VW camper vans and I myself have done this mod on my brothers VW type 25 devon camper.

The second battery is better if it is a deep charge battery as this can be drained and recharged many times without degrading, A normal car battery isn't designed to be drained constantly and provides more of an instant punch to start the engine.

You would connect the positive of the second battery to the first via a relay, connecting terminal, 30 from the main battery positive feed and using terminal 87 to feed the positive of the second battery, earth the secondary battery in the normal way with a decent earth lead.

The basic idea is to have the second battery connected whilst the engine is running so that it is charged with the main battery, but when the engine is off the feed off everything is taken from the second battery so even if this is flat the main battery can still start the car.

To enable this you locate the blue wire on your alternator (terminal B+ typically) which when the engine is running energises and makes your alternator light go out on the dashboard. this goes to terminal 86 of your relay. The terminal left over on the relay (85) goes to earth.

Obviously this is a condensed version of things to give you an idea of how to do it, as I say most marine and camping applications use it and I have seen it used on monster hi fi systems to good effect.

hope that helps.

[jasonpi]

cheers mate, will give it a go

[Dizzie]

isn't the idea of a 2nd battery purely so you can run your ICE without the engine on? It doesn't give you more power. that's governed by how many AMPs your alternator can output. 120A for me

[tobz.]

.

isn't the idea of a 2nd battery purely so you can run your ICE without the engine on?

I thought the idea of a second battery for your ice was to keep your amp power leads as short as possible thus eliminating the huge voltage drops associated with long leads running from boot to bonnet

[Dizzie]

Use 0 gauge cable then!
I've got 14.3 volts in the boot!

[diagnosis-dub]

Surely if your running just the ICE from the second battery then your not going to suffer a power loss as much as running the ICE from the main vehicle battery.

My logic here is that a normal car battery supplies all the systems in the vehicle and sticking the car stereo onto this must add more drain, feeding the ICE straight from the second battery will supply it with uninterupted power.

I would agree with you dizzie though and say that the main reason to do it is so that you can have your vehicle parked up and the stereo on and not have to worry about the main battery going flat.

[GazB]

If you use a splitcharger, the stereo will run from the second battery, without draining the main battery.  Thats what I was told when I did mine.

[monzablue16v]

Rightey ho here we go!

Split charging is used mainly in large ICE installs and is used to charge one or many high capacity deep cycle batterys (optima red tops yellow tops etc) sometimes gel batterys and sometimes leisure batterys. The extra batteries serve several functions.
1. use the system when engine off until flat and still start your car.
2. more amps to your amps
3. takes the power to charge from your alternator inline with your main battery
4. allows use of larger amps as there is more exclusive current
5. less current draw on the alternator and other vital components.
6. stops the lights dimming when the bass drops

If used inline with a power capacitor you get even more ampage available which means crisper deeper sounding stereo systems.
Think I'm going to overhaul mine in the winter and might go a little crazy! 2 x 15" Rockford Subs 2 12" Rockford subs in rear panels 8" Rockford subs in the doors now that's going to take some serious head scratching and some serious power!!

[Judderi]

Heres some interesting reading for you all. I found it when shopping for a large power cap. Let me know what you guys think too.

http://cgi.ebay.co.uk/Xstatic-Model-300-BatCap-Battery-Cap-Farad-NEW-2005_W0QQitemZ5790779112QQcategoryZ4950QQcmdZViewItem