hey guys, Im thinking of hooking up a secondary battery in the boot to solely run my IES (Incar Entertainment System/CarPC) But have a few quiestions.

1. How does the secondary battery recharge?
2. Who would install a secondary battery?
3. How safe are batteries in the boot?
4. If the secondary battary goes dead does it effect the primary battery?

Thanks all in advance.

This question seems to be asked alot on audio forums. Most people say no, its not worth it.

Theres two ways to run two batteries, the first, and cheaper way is to run to identical batteries in Paralles (or is it series :S). Basically, the only increase in performance you get is the extra reserve capacity, ie, 1 battery goes flat in 2 hours, the 2 batteries together last 4 hours. In this method your pretty much making 2 batterys work as a large single one. Both batteries will tend to go flat together aswell.

The second way is to do it the 4wd way. This is quite expensive. you need an isolator ( or something along those lines).This allows power to be drawn only from the boot battery when the cars off, leaving the engine battery strictly for engine starting duties. Downside is you dont get any increase in reserve capacity, as only the rear battery is working for the audio, ie, 1 battery for audio. The big pro is that your car will always start.

The next issue is the legal issue about needing to vent (even sealed, gel batteries) to the atmosphere. I think this rule depends on the state, it would be best to speak to an engineer or someone in the know to confirm.

hey guys, Im thinking of hooking up a secondary battery in the boot to solely run my IES (Incar Entertainment System/CarPC) But have a few quiestions.

1. How does the secondary battery recharge?
2. Who would install a secondary battery?
3. How safe are batteries in the boot?
4. If the secondary battary goes dead does it effect the primary battery?

Thanks all in advance.

1. Its in parallel with the primary battery, so it gets the charge voltage as well.
2. An auto electrician.
3. If in a battery box, bolted to the floor of the boot, with the correct gauge of cable, with strain relief + grommets, fuse (at or as close as possible to terminal), it shouldn't be a problem. There is some hydrogen produced when charging, but this is minimal.
4. If its properly installed, it will have a low voltage isolator (like you use in a 4X4 for accessories). This will disconnect the battery if its voltage drops too low and there is no charge voltage (to avoid running the main battery low).

make sure your 2nd battery is a deep cycle battery, or it wont last long, (im on my third)
wire it up in parrallel, with a relay, that isolates yours system from the car battery when the ignition is off, and so that both batteries are connected in parrallel when the engine is running (ie to charge your deep cycle battery)

oh and your boot has a outlet only vent port, on the passenger side, near the tail light

well the plain is to run my CarPC off the other battery when the car is off so if it dies i can still start the car then the main battery would charge the secondary battery (cause its dead).....is this line of thining right when hooking them up in parrelle

The 4x4 isolation kits cos about $160 from battery world and can be installed by anyone with a half decent knowledge of car electronics and half a brain. they give you all the instructions and its pretty easy to follow.

this method is alot better in many ways as it decreases the load on your alt. and increase the life of your bat (according to the guy at bat world) and if you are going to do this then i would invest in a yellow top so that it lasts cos if you are thinking that you need a second bat you will prob be draining it lots

You will need to vent to atmosphere

Simply put the battery in a small box, put a small flexible pipe into it, seal it all up and lead the pipe out a vent.

You dont need large gauge cable for your secondary battery, 4 gauge would be adequate id imagine.

You will need to fuse the battery at both ends as close as possible to the battery, if you get into a rear end the rear battery shorting against the chassis is as dangerous as the front end.

Not rocket science though, I also suggest you go a dry cell. optima yellowtop d34 will last you for years

you can get isolators from $60 depending on where u look. most will go for around the $90-100 mark. just make sure u get 1 with a time delay on it... otherwise your connecting both batteries soon as ACC switched which will cause it to start from both, blowing ur fuses/burning out ur wiring and killing ur nice new deep cycle thats not designed for starting.