I have two questions:
1) I've moved my battery to the rear tire well using '0' gauge amp wire. The ground is screwed into the tire brace (I ground off the paint first) at the rear and at the front I ground some paint off the chassis and screwed the original negative lead from the engine to it. When I start the car it is as though the battery is almost drained. It this a connection issue or a result of the length of the positive cable? For instance, some of you guys have welded a bolt in to serve as negative mounting point at the rear.

2) I've looked through a number of the threads on this subject and I'm still puzzled. Do you need to vent the battery because it's in a confined box or because it has been moved into the passenger compartment? Mazda Miata,BMWs etc have batteries in the trunk with nothing more than a piece of fabric to cover them. Are these necessarily "Dry Cell" batteries or is venting just a racing issue once the battery has been mounted in a box that would allow vapours to accumulate? Thanks, Jon

 

Ok uhm if i am correct the battery needs to vent. Now that being the problem prolly not. Secondly being that far it could be possible that it not getting enough charge. Secondly the negative needs to be grounded on the frame or engine. The engine the best. One thing i need to ask y did you move it back there?

 

Batteries need to vent when charging. This is interesting however because my gf's old saturn had the battery in the trunk too. I never looked inside of it so it may have been a dry cell battery. He probably put his battery back there for better weight distribution, those things are heavy.

 

the only reason you want it to vent so it dont' build up gases that could ignite and explode thats all i am trying to say. B/c batteries give off gases and it could explode. It may not so up to you.

 

Actually I haven't comitted to moving it yet. I can use the positive wire to run my amps for the stereo if I leave the battery at the front if I want to. The reason for getting into it though is that I'm in the process of changing the intake and mounting a cold air system. Depending on hood clearance etc. I might want the battery space in the engine bay for an air filter.

As far as the gasses go; I'm still unclear if such gasses are likely to accumulate to a dangerous degree if the top of the battery is left uncovered or only if the battery has been mounted in a protective box like the racers use.

 

I'd be worried about breathing in the gases too. I don't know if there is enough gas given off to amount to anything though.

 

You definately should not have a regular battery in your passenger compartment unless it is in a sealed container vented to the outside. The fumes are toxic.If the battery were in a trunk, not the passenger compartment, it may not be as big of an issue. You need an Optima battery if you want to move it to the rear of the car as they do not vent.
How old is your battery? all that wire will take up some juice and it may just be that your battery is old. I didn't notice too much difference when I did mine but I also bought a new Optima when I did it.

 

I should point out that in my gf's car the trunk was a completely seperate part of the car from the passenger compartment. In the thirdgens the trunk definetly IS part of the passenger compartment.

 

Steel is a very poor conductor of electricity. Hooking up to a brace might give the current limited pathways, going through a few spot(weld)s only. The best would be to bolt the negative to a point where 2 or more sheets are joined, giving the current a chance to spread in all directions in as thick metal as possible. After all we're talking about 200-250Amps in the connection point here. Doesn't take much resistance to give a voltage drop.

 

Very true. Fullsizewagon. All you need to do to ven it is close it and use a hose and vent from the side to the bottom of the trunk... And it don't matter if the trunk is separate or not. i will tell you you're trunk isn't fully enclosed by its self all there is between the carpartment of the inside of the vehicle to the trunk (Jccaclimber) is foam and springs from the back seat. It isn't completely sealed from fumes from the trunk thats y you don't put gas cans in the back of the trunk b/c it will fume you out. If you don't believe me try it.. or take my word for it. But i am not here to argue its there go ahead and keep it but dont' let this advice not go away. Thats why most car batteries were in wear the engine was. Besides a volkswagen which were not talking about it was under the seat in the car but was vented and inclosed in a box to go out in the back where the engine is. Okay enough of this talk about if its safe or not. The point is that you need to make sure its well grounded and if you're not getting juice from back there put it back wear it was orginally made for. B/c i am assuming you're putting the battery back there so its more accessible for a car system to hook up an amp. If thats the case just run the wire back to the amp and ground it to the trunks latch its worked for me when i had a car system in just get a connector to run the bolt in and bolt on the latch works perfect for a ground.

p.s if you put battery back there try and run a ground to the latch and see if that works for the battery assuming it will. yea lil more wire to run there depending where you're battery is at. Just putt it under the carpet and bolt it on and try it.

 

I have relocated my battery to the back and ran 1 gage wire for the positive. For grounding, I put a 1/2 dia bolt through the floor where the rear "bumper frame rails" are and it goes through that too. I have no voltage drop problems what so ever. Up front, my 2ga ground wire goes from the passenger lower control arm bolt directly to one of the two starter bolts. Of course the positive cable goes directly to the starter solonoid. Maybe your grounds are not in a heavy enough place, like these other guys are saying. And besides easier amp hookup, relocating the battery is helping distribute weight off the front and putting it over the rear tires. And cleans up the engine compartement. A win win, uhh win, in my opinion!

 

Thanks to every one who has chimed in here. Vortec350 for the 1/2 " ground bolt did you weld it in place or just bolt it in tightly?

 

I just bolted it in with star washers, but welding would definetly be better. Then you know it's making good contact.

 

I'm in the middle of this myself but can't yet report success. However, I found that permatex makes a copper anti seize compound. I'm using it for all my body connections and hoping it will provide better grounding paths to the chassis as well as long term corrosion protection. We'll see.

"Permatex® Copper Anti-Seize Lubricant
A premium quality copper anti-seize and thread lubricant that may be used to prevent seizing, corrosion and galling where high temperature conditions exist. Contains a high percentage of micro-fine copper flakes in a semi-synthetic grease carrier and is fortified with high quality rust and corrosion inhibitors. Temperature range: -30°F to 1800°F (-34°C to 982°C). Provides good electrical conductivity. Meets Mil Spec #907E.

Suggested Applications: Spark plug threads installed in aluminum, exhaust manifold bolts, engine bolts, oxygen sensors, knock sensors, thermostat housing bolts, fuel filter fittings, and battery cable connections"

 

I wouldn't plan on running down the drag strip anytime soon with the way you're doing this. The battery will need to be in a metal battery box with a clearly labeled battery kill switch mounted on the rear exterior of the car that will kill ALL power to EVERYTHING in the car when in the off position. The ONLY plastic battery box that is legal by NHRA standards is a Moroso box.

 

I moved my battery to the trunk and I grounded the battery in the trunk by welding a bolt to the sheet metal and running a short peaice of cable to it. Then I ran and extra ground wire cable from the battery to the back of the engine block. I also kept the stock ground cable from the front of the engine block and grounded it the front sheet metal. It may seam like overkill but I wanted to make complete sure my grounds were solid.

 

OK, so I finally got back to this project. I re-mounted the negative lead from the battery to a 5/8 bolt in the tire well. That made a difference to the voltage drop but didn't solve it alltogether. Up front I had the engine temporarily grounded to the fender well so I mounted another 5/8 bolt through the front frame rail between the back of the headlight and the rad support. This had no effect. I turned my attention to the positve wire which was still attached to the original battery cable to take the current down to the starter. After attaching it directly to the starter there was another noticeable improvement. Up to this point I was still using the old Delco battery (650 CC amps). After installing an Optima Red Top with 800 cold cranking amps the car starts as it should. Success!! Next up, I've decided to to shift the battery out of the tire well and into the cargo compartment. I'm going to fab up a plate steel surround for some crush-proofing in case someone rear ends me at a stop light (my friends keep asking me why I'm building a bomb so close to the baby seat!). Jon