Switch for dual batteries?

**RS3RS** · 10-21-2005, 11:26 PM

This isn't carputer related, but it is automotive electronics, and I figure you guys would be the ones to ask.

Basically, I'm turning my 2003 Ford Focus SVT into a part-time mobile automotive detailing rig. I have a battery powered shop-vac, but I need a way to power my polishers and carpet extractor (which is only 360 watts), and I don't want the noise of a generator, so I bought a 3000 watt continious / 6000 watt peak invertor.

The thing is huge, and I just barely managed to squeeze it behind the passenger seat. I've got 0 ga. ran from the battery to it, but not hooked up yet. I'm wanting to get an Optima yellow-top deep cycle (or 2, depending on how well one works for me) to hook up to the inverter so I can run my equipment off it instead of the cranking battery. My question is this:

Can I put an optima yellow top in the back seat area, with the inverter, and run 0 ga. to the battery, and use some sort of a DC switch (a DC circuit breaker switch is the only thing I'm finding rated for 250+ amps) on the 0 GA wire running between the cranking battery/alternator and the Optima yellow top? The battery and invertor would be grounded somewhere by the back-seat area.

That way, I could charge the optima while I'm driving, but when I want to run my carpet extractor or something, turn the switch off so that I'm not pulling power from the cranking battery.

I just want to make sure it would be okay to ground all of this on a seat-belt type bolt, and that nothing will spark/explode when I turn the switch on-off?

I'm not much of an electronics expert, so I figure I'd better run it by you guys before I kill myself somehow. I don't really see the need to spend the money on a battery isolator, when it seems like a simple switch could do everything I need?

Input is much appreciated. Thanks guys.

**xdjxklusivex** · 10-22-2005, 12:02 AM

damn dude i forgot what its called but im gussing battery isolator its been discused on here bfore if u do a lil search u can find out about it people do it for car audio and huge carpc systems so u might wanna browse through the car audio section u might find something good

good luck!

wanna detail my car? lol

**RS3RS** · 10-22-2005, 01:28 AM

Yeah, an isolator seems like it would work... The only problem is I can't find one rated for more than 200 amps. Not that there's probably any chance that I'll be running 200 amps, but since my lines are fused for 250 amps and everything, I want to make sure the switch/isolator can handle anything I throw at it without blowing up.

That's why I was thinking a circuit breaker switch, since I've found those rated for 430 amps+ at 12 volts (and they seem to be cheaper than an isolator) would be good...

*shrug*

**aoLhaTer** · 10-22-2005, 02:12 AM

200amp is usually as high as you can find

Thats a tremendous amount of power
Id recommend either Surepower or this one made by PAC http://www.pac-audio.com/products/relays.htm

**RS3RS** · 10-22-2005, 02:19 AM

Originally Posted by aoLhaTer

200amp is usually as high as you can find

Thats a tremendous amount of power
Id recommend either Surepower or this one made by PAC http://www.pac-audio.com/products/relays.htm

Okay, thanks for the input. If wost comes to worse I'll just get a 200 amp one and buy a 200 amp fuse or something.

What do you guys think of something like this? Any problems?

http://cgi.ebay.com/ebaymotors/Perko...82903305QQrdZ1

Says it's rated for 250 amps continious, which sounds perfect for me. Think I'm going to just buy this if I can't find any reason not to.

One more question on the wiring of the thing - Is it okay to just ground the second battery like you would an amp. to a seatbelt bolt or something? And if I used a switch to isolate it, I would I need to switch-off the negative/ground connection too? Or just the positive connection to the main battery / alternator?

Thanks!

**aoLhaTer** · 10-22-2005, 02:45 AM

That manual selector would do but whats key about it is that its manual
An isolator will automatically select the proper battery for you (in essence) and it will charge both batteries at the same time when the enginer is running. The manual selector will only charge the battery thats selected (this is the biggest problem)

The second battery should br grounded with large gauge cable as short as possible to the body of the car. The paint should be chipped away so that its touching bare metal

You wouldnt need to switch the ground

**RS3RS** · 10-22-2005, 03:56 AM

Originally Posted by aoLhaTer

That manual selector would do but whats key about it is that its manual
An isolator will automatically select the proper battery for you (in essence) and it will charge both batteries at the same time when the enginer is running. The manual selector will only charge the battery thats selected (this is the biggest problem)

The second battery should br grounded with large gauge cable as short as possible to the body of the car. The paint should be chipped away so that its touching bare metal

You wouldnt need to switch the ground

Awesome, thanks a million man!