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jeffandre
01-02-2005, 02:52 PM
I am planning to wire 2 12v batts in parallel, so what do I need to take care of? Can I just set them up and forget about it?

Can I wire each of them seperately to ground (instead of running a wire from one batts negative to the other batts negative)? I would be grounding each batt seperately but to the same piece of metal, just on opposite sides of the driveshaft tunnel.

Any tips/hints on lug/terminal ends and setups? Thanks in advance for any help you can provide,

spanky the wondermuffin
01-02-2005, 04:41 PM
it depends if you want both batteries to run the starter.if no,buy a heavy duty battery isolator kit.make sure it is rated for the output of your alternator.if you want both to crankthe car painless has a dual battery set up that use a big relay to connect the batteries.i have one in my tow rig.don't think you need it for a car.grounds can go anywhere,but the safest way is to tie them together and run them through a shut off switch on your dash.use a dual pole switch and isolate your alternator with the other pole.if batts. are in the trunk run oo (double aught) cable.your local parts house like napa should have cable,ends,and a crimping machine.i think it is worth it for the couple buck they charge(if at all) for a nice machine made crimp.are you putting them behind your seats?i had my (one) battery behind the pass.seat,but put it back into the trunk after a season.it's a big chunk of movable ballast,and i need rear weight.finishing the car,putting it on wheel scales,then moving them around until you found the most advantageous spot would be ideal.don't forget to size your alt wire based on output and run length.i use 4 gauge with a 150 amp fuse.i also use a furd style starter relay.the batteries need to be the same size and age.if you manually disconnect them from each other or ground upon shutdown you don't need the isolator.why 2 batterties?

jeffandre
01-02-2005, 04:54 PM
Spanky,
Thanks for the info, I'll be using it this week as I continue designing the battery setup. I decided to use 2 Odyssey PC-680's (12v, 7"x7"x3" thick) and mount them directly under the seats. The area from the car floor to frame edge will allow me at least 1/4" of clearance once I install the steel boxes that hold the batteries. This will move the weight very close to center, just makes it tough to maintain without lifting the car in the future.

I have a lot to learn in this area, was hoping to get the batteries installed over the next few months as well as figure out whatever other gadgets I need to optimize the system for future use.

David Pozzi
01-02-2005, 09:54 PM
I put the battery in the trunk of my wife's 73 Camaro: http://ourworld.compuserve.com/homepages/David_Pozzi/second_gen_camaros.htm

The major drawback to a second gen weight balance is too much front end weight. Moving the battery to the trunk will reduce front weight the most. A firewall between battery and driver is required for most speed events. If you put the battery in the passenger area, you may not be able to drag race the car and probably not open track it.
David

jeffandre
01-03-2005, 09:10 AM
I put the battery in the trunk of my wife's 73 Camaro: http://ourworld.compuserve.com/homepages/David_Pozzi/second_gen_camaros.htm

The major drawback to a second gen weight balance is too much front end weight. Moving the battery to the trunk will reduce front weight the most. A firewall between battery and driver is required for most speed events. If you put the battery in the passenger area, you may not be able to drag race the car and probably not open track it.
David

I had the regular battery in the trunk for years but have little room now that the fuel cell is in there. I figured it would help the cg if I placed the battery low and towards the center of the car. That and lack of room led me to 2 batts that are very thin.

My plan was to mount the 2 batts underneath the car, directly under the two dfront seats, but I could try to mount them next to the fuel cell (one on each side, they are only 3.11" thick). I would build a box that recesses through the trunk floor to lower them as much as practical. I could install them under the trunk in boxes placed outside of the leafs, not the optimal placement for weight. It gets down to a choice between mounting them low and centered or rear and higher.

David Pozzi
01-03-2005, 09:38 PM
I wouldn't place them outside the leaf's, that area may get hit if you spun out and dented it. No sense making the car un-driveable due to a dent if you have a mishap.

so the trade off is between CG height and F/R weight balance.
If the front is not very light, I'd favor the bat in the trunk and CG height will just have to suffer. I would think weight over the rear wheels is more important for traction than any gain from a slightly lower CG. The main advantage of our cars is horsepower but getting it to the pavement is critical. Higher horsepower requires more traction any way you can get it.
Check the rules about battery placement.

F70t/a
01-03-2005, 10:55 PM
Hey jeff,

That sounds like a sweet a$$ set-up your doing. make sure you take a bunch of pics. I think I might end up doing the same when the time comes :ssst:

spanky the wondermuffin
01-04-2005, 08:08 AM
is it a plastic cell in the trunk?sorry but that won't pass tech in most places.i had the same set up in mine.i slung a fuel safe cell in the stock location.i'm replacing it this year with the same size but deeper for more capacity.current is 18 gal.,i really have to featherfoot it to get to the end of the pony.i'd like 25.i'd entertain an offer of $500.00.it has 2 -8 pickups,a surge tank,vent with check valve,and a gm sending unit.it was built in spring of 2002.special bay area price,i won't ship,or sell it until the replacement is installed.

jeffandre
01-04-2005, 07:47 PM
Thanks for the discussion, I am heading towards placing the batts in metal boxes under the trunk next to the fuel cell (moves weight rearward while keeping it as low as practical).

Dave,
I will check the NASA rules tonight, but my boxes will be 3/16"-1/8" thick, fully enclosed, so hopefully no problem. Otherwise they will go in the trunk, 1 on each side of the fuel cell, maybe even dropped through the trunk floor about 3".

F70/ta,
Pics will be coming as soon as I get my crap together...

Spanky (Jon?),
I have an aluminum 20-gallon cell in an enclosed steel container that is dropped through the trunk floor. It sticks about 7" down, so with the lid covering the vent and return fittings/lines it also sticks up in the trunk a bit. I wanted to keep it low for handling as well as have some trunk space left for golf clubs/luggage for those overnighters. What are the dimensions of your Fuel Safe cell? My fuel cell containment area is 24" square.

spanky the wondermuffin
01-05-2005, 05:08 AM
that is a major step above a plastic cell in the trunk.my cell is around 35x24.off the top of my head.fuel safe can make a custom bladder to fit your container should you ever need one.both batteries on the right side will be best for balance.you know your left side weight is going to be high,along with the whole nose.if you jack some weight into the right front it will also add weight to the left rear.the batt. can then add to the right rear.

jeffandre
01-05-2005, 07:11 PM
Spanky, how did you know my left side wieght would be high??? j/k :doh:

The batteries weigh 13 pounds each, not sure if I have room for both on the right side back there but I will look. I have not started building the boxes or setting up the new cables so I can basically plan anything at this point. I actually did think of mounting 1 under the passenger front seat and 1 behind it in the rear passenger foot area (fully enclosed in a 1/8" netal box accessible from underneath only).