How many car batteries have you looked at if you think that they are all sealed? Almost all batteries are vented and not sealed only a few are sealed so you need to use a sealed battery so you don't vent fumes into the car....

I think you're misunderstanding the requirements... Like I said above. It can be any battery but it must be stored in a SEALED container which is VENTED to the outside.

what amps are they? I'm pretty sure you money would be better spent on a single good battery, i got my D34 yellowtop for about 300 or slightly more from memory. That's a lot less than what you will pay for a proper dual battery set up

G'day

Ive looked into this time and time again, the advantages are good and the disadvantages arn't that pronounced.

My car, 89 xf ute with 250 crossflow.

The way i looked at my situation was this, being a construction worker i like to have all the doors open and run the stereo up loud enough that i can hear it over the noise of the job. At the end of the day the battery is flat and cant start the car. This is a problem for 2 reasons, one the battery is flat and car wont start, 2 it decreases the life of the battery.

My stereo consists of the following, i run a pair of response splits, a pair of 6 inch pioneer 4 way coaxles and a kicker l7. The l7 runs off a response 800rms monobloc and the splits and coaxles run off response 4x100. Now when i have it going to where i like it it can draw up 2 100 amps with an average of about 35-40. Bearing in mind that this is all with the car off.
Now when i did the wiring the first time i did it with 4 gauge cable running through the usual fuse holder to each amp straight off the battery. When the car was running i had no problems with head light flicker or anything like that. I did all this with a century battery. I managed to flaten it to 10 volts in about 90 minutes. That was no good.

The next step was to add a cap to my system, this made a good difference. It then took 180 mintues to flatten it down to 10 volts. This still wasn't enough for me as i also run a car fridge all the time and this draws current aswell.

I changed to a d34 optima yellow top for my battery and this made a bigger difference, i got nearly 6 hours out of it before it went to 10volts.

Now for the dual battery setup, i chose to run the century battery as my main battery for the car and the optima for the stereo and car fridge aswell as extra points to run other things. I used a 150 amp isolator by projector which i bought off ebay. I wired it up how the instructions said and ive had no dramas since.

Now for the argument that it puts more strain on the alternator. I run an 85 amp alternator from an ea. The way that the isolator works is that it directs the charge to one battery at a time. It directs the charge to the battery with the lowest voltage. What i'm not sure about is what happens when the second battery is flat when you first start the car. I assume that it directs the charge to that battery until it reaches the required voltage.

What you need to look at is what you are doing with the vehicle, ive outlined my situation and thats why i have done what i did.

Cheers

Sorry dude but I agree with Outlaw and know from experience dealing with several engineers over the 2x gel cell and single dry cell batteries in my boot setup.

To comply with ADRs, NCOP and VSB compliance, the battery must be fully enclosed and the enclosure vented externally to the outside of the vehicle to eliminate the risk of exposure to harmful fumes. Electrically insulated enclosures such as marine battery boxes are the preffered enclosure type. Battery boxes must be securley fastened to the vehicle and all cables shielded where necessary to prevent damage from external sources such as road debris.

Your 'normal' type lead acid batteries generally arent sealed. They vent to the atomosphere. Actual 'sealed' lead acid batteries such as the dry/gel cells used in my own setup, do not require a 'sealed enclosure'. They must still be mounted down to avoid being thrown around in your boot. However unlike a conventional battery these battery types do not vent nor spill. Enabling them to be mounted on their side and in some cases even upside down.

Just note when referring to conventional lead acid batteries needing to be enclosed in a sealed battery box that vents externally...I'd like to highlight as in Mongooses post that this means vented externally to the vehicle not just the enclosure itself as this would mean fumes are still expelled into the vehicle cabin puttin occupants at risk. (This is why you see additional batteries on utes and trucks side mounted or mounted under the vehicle, past the rear windows. As this way the fumes cannot enter the cabin).

Last edited by Big Kev on Sun Dec 23, 2007 7:01 pm, edited 2 times in total.

Well I am willing to stand corrected when I'm told I'm wrong by two people

That is what I was told by a couple of people way back when I did my botchy twin battery setup so I assumed it was right. My apologies

On your original query you mention you plan to run 2x 1500w RMS Mono amplifiers for you subs. I take it the 1500w RMS is the PEAK power rating at say 1ohm....What power output are your subs? Will they actually use the available power from these amps.

Also 1000w for you speakers....that a fair amp to run speakers...what amp are you going with for this job...again will your speaker choice make use of this power?

100A alternator will run alot of systems without issue. Your best bet will be to upgrade your existing power cabling. Then see if your lights dim etc when music is played at decent volumes....First call is then to look at the current level of current being pulled by the system and calculate that load on your current alternator/battery combo. The battery may then require an upgrade.

As Stone has also mentioned having the vehicle off etc will play apart in this and how fast then batteries are drained. This is where high amp/hr batteries come into play with large reserve capacities. As they will assist in supply additional current when required for those big bass notes etc along with enabling you to play your tunes for lengthier periods when the ignition is off - all to an extent though....depends on the realistic outcome you go with and the relative components used