Can I put an extra battery in my Chevy?

Hi, guys!
I'm new to the forum, but not to MP3 cars. I have had an old box in the car for two years, but now I want to really beef it up. Everything is ready, except for the power part.

Now instead of using an UPS connected to my inverter (I need the regular AC PSU since I plan to use the media computer indoors as well at times) I want to use an extra battery in my Chevy Sub 5.7 litre petrol car. If not I loose power to the PC every time I turn the key to start the car and have to restart it. My wife does not like that. :D And what my wife does not like, she does not use. It took me forever to get her to use our multi-zone sound system because it was flakey at the start... I have two options: A regular 40 AH car battery and a motorcycle battery, 24 AH. So the questions:

1. Can I put this battery in the back of my car? I know some gas comes from batteries, but will it be enough to be dangerous in a regular use family car? If necessary I could run an air hose out somewhere, but I'd rather not. And no, there is no room for that battery in the engine compartment without major surgery, and I don't want to do that since I don't know if I will keep this car forever. I'll probably buy a newer Sub at some time (my wife won't have anything else as the main car), and I want to be able to move this to the next car without any big problems.

2. Can the stock generator take an extra battery? I believe it's a 100 or 110 amp generator in this car.

3. A guy I know advised me to hook it up directly to the generator, not the starter engine, to make sure it won't drain too much power when starting the car. Is that smart?

4. Would you go for the larger size car battery inside a plastic battery box (I do have the room, but it won't look as good) or would you take the motorcycle battery and put it underneath the seat? I guess that MC battery won't let me run the stereo that long (it's a regular Pioneer headunit driving the speakers in the back doors with one SoundStream Little wonder for the twin 12" subs and one 4x50 W Arizona Eagle (local brand) for the main front system), but maybe I could use it only for the PC?

5. Finally: Would an even smarter solution be to hook an even smaller MC battery (I can get them very cheap) just for the inverter? Or would that battery just be flattend the second I turn the key?

I hope some of you power gurus out there can help me! Thanks a lot in advance! :cool:

A regular battery should be vented if placed in the trunk or hatch area of a car. According to NHRA rules, which are created for 'crash conditions' of a vehicle, you would need a firewall between the passenger compartment and a battery placed in a battery box. I would recommend, if you were to put a battery in the passenger area, you should used a sealed one such as an Optima or look into a Gel Cell. Maybe Holley's (Reactor's) mini sealed battery. It's about the size of a motorcycle battery but puts out the same amount of power of a regular size battery.

- Jeff

Thanks, I'll probably vent it, then. The main point is not spending too much on this project, I want to keep it low cost. A regular battery with box and cables will cost me around 50 dollars here in Norway, any gel batteries will be at least 200, probably more.

The sub and other full size Chevies were available from the factory with dual batteries as an option or standard for the police packages. So you should be able to search junk yards and /or auto body shops for the other side battery tray and simply bolt it in. Ideally you want a battery isolator so the two charge but remain seperated for loads and then use a deep cycle battery as opposed to a regular battery for the player.

Thanks! I'm afraid the norwegian scrapyards are rather empty on Chevy parts, but I just called a friend who makes and competes with off road racers and he said he'd make the tray for me in exchange for an old computer I had sitting around. We only have to move the vacuum tank that's placed where the second battery has to be. And he also gave me battery isolator. The only problem is that it says it's rated to 70 amps, so do you think that will work on this system? It's originally made for a V8 power boat engine. And I even have a spare stock battery for the car, so this isn't going to be as expensive as I feared! :D

Have you considered a tank circuit?

Cheaper than a second battery, you don't have to worry about relays or charging two batteries or whatnot, and you don't have to worry about venting... Might be quite a bit simpler...?

You won't get the extra time when the car isn't running, but is that an issue?

Additionally, what type of UPS do you have? If you have one that uses a 12V battery then you can probably wire the car directly into the UPS battery input and skip the inverter altogether, saving a little bit of inefficiency *and* the UPS probably won't shut off when you start the car.

Just a suggestion. You might want to search around here and on google for "tank circuit" and wiring a UPS directly into the car.

The point is that I don't have a UPS. I was planning on getting a used one, but when I found out that my car is delivered with dual batteries for some applications that only strengthen my resolve to do it that way. The second battery will be in the stock placement, I only need to find out what to do with the vacuum tank that's there now...

If you don't have an inverter either then you might want to save your pennies and just get a used UPS with a dead 12V battery (you can get those for pretty cheap because they're not very useful to other people)... Yank it out, wire it directly to the car, and you don't have to do anything else. Sounds a lot simpler than moving a vacuum tank and buying stuff that you don't need.

Thanks, but I do have one.

UPS's usually don't make good invertors, a lot of the cheaper ones don't dissapate heat well enough to run for long periods of time, usually just the 1/2 hour the battery runs out. I think on the dual battery burbans the vacume ball is under the battery tray. The nice thing about having a second battery is you can run a seperate wire from the battery straight to the mp3player/head unit for better sound isolation, the battery acts as a big filter cap. I plan to add one to my truck soon but I don't have as much room under the hood as you :(.