Trunk mounted battery questions.

[Hertz]

I've only got 1 ground (in trunk). The most voltage I ever see (at the dash) is 13.00, the most I've ever seen at the ignition (turbo timer) is 13.5. Sometimes when running a ton of accessories (seat warmer, headlights, radio) I get 12.00 which makes me a little nervous.

I'd much rather have 14.5 volts all around, so I'm (eventually) going to run a ground up to the front. I think that'll make the difference.

 

[14u2nV]

Mine is grounded in the trunk, to the shock tower, and I get 14.5 volts on my palm. Havn't got my volt gauge hooked up yet.

 

[turbowop]

The battery being in the trunk should make no difference on how much voltage you read while the car is running, since the alternator is feeding the voltage at that point.

My car is a bit different, however, since I have a kill switch. My alternator wire runs all the way to the kill switch in the trunk, and then all the way back to the engine bay where the battery used to connect. Using 4awg to the battery from the alt, and 2awg from the battery back to the stock location I see about 13.6 volts when cruising during the day (depending on how warm the engine bay is) and at night with headlights and such on, I see about 13.2 volts. That's with a brand new Bosch 90amp alternator.

 

[14u2nV]

Quote:
The battery being in the trunk should make no difference on how much voltage you read



With a bad ground at the battery, the alt has more of a strain on it to make up for lost "stored" energy, thus making the alt output lower.

 

[fastasleep]

I just thought Id update with a VERY important note and a pic.

In this pic, note that I SHOULD have a rubber grommet around the (+) battery-to-breaker cable where it passes over the aluminum box. The cut-out for the wire has a sharp edge and could eventually slice through the sheathing causing SERIOUS ELECTRICAL FIRE. This is the purpose of the breaker so that if connection is broken between the fuse under the hood and the breaker in the trunk, an increase in amperage (> 140amp) will trip the breaker and cut power (so as to avoid fire). It is IMPERATIVE that the breaker be as close to the + battery terminal as possible with as little chance for unwanted contact as possible.

and a pic of my HKS airbox suckin air like it should have from the factory /ubbthreads/images/graemlins/smile.gif



I dont mind answering questions through PM, but Id prefer they be posted here so that everyone has access to the information.

 

I was wondering where you got you battery box? I'm in the middle of doing this myself and wondering if I even need a sealed box because I have a sealed battery. I was doing some searching and looked at some pics and noticed that most people using the sealed battery's did not use a sealed box. I just wanna be sure before I go any further.

 

[atc250r]

Jeg's makes a box like that and so does Taylor. The Jeg's one is a lot cheaper though. Technically, if you are using an Optima type battery you shouldn't need a box at all since there is no acid in it or fumes coming out BUT you probably won't convince the tech guy at the drag strip of that. Besides, IIRC the NHRA rules make no special provision for those type of batteries, they want all of them in a sealed box vented to the outside.

Jeg's Box

John

 

I was looking at the jegs one earlier, and I'm probably gonna get the aluminum one. I wanna see if my friend can make me one first, but for $120 I might just get it. I'm gonna wait on the disconnect switch to see if I get called on it, but when I do everything I'll make it so I can do it easily.

 

http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_745314_-1_10367

This is what you want if you are going to go that route.

I like using a smaller batter and keeping it in the engine compartment more then a remote battery. But when it comes to having to have the required shut off for sanctioned racing then the battery in the trunk is the best option.

 

[OldHairyBastard]

Seat Warmer??????????????
Quote:
I've only got 1 ground (in trunk). The most voltage I ever see (at the dash) is 13.00, the most I've ever seen at the ignition (turbo timer) is 13.5. Sometimes when running a ton of accessories (seat warmer, headlights, radio) I get 12.00 which makes me a little nervous.

I'd much rather have 14.5 volts all around, so I'm (eventually) going to run a ground up to the front. I think that'll make the difference.

 

Probobly an aftermarket cigarette lighter one..

 

[CP]

If anyone is interested in a sealed plastic battery box, PM me. I've got one that I was going to install before I decided that my car will never touch a drag strip again. I can send pics this weekend if there's any interest. I'm pretty sure I got it from Summit. It's big.

 

[jepherz]

Quote:
Probobly an aftermarket cigarette lighter one..



No, he installed them off a mercedes or something.

 

[fastasleep]

Thread Resurrection!

I need to improve my grounding I believe. Right now, I'm grounded to the strut tower on top of my rear strut tower bar, but I don't think it's cutting it.

Do I want to run just one big (4AWG or 2AWG even?) wire up to the engine bay? Or multiple grounds off the (-) battery terminal?

I assume grounding the motor to the chassis in additional places would be beneficial?

 

[turbowop]

I haven't had any problems with mine grounded to the strut tower and it's been that way for like six or seven years now. Did you sand off some paint to make a good connection?

*edit* On top of the strut tower bar is how mine is also, but I had to sand off the powdercoat where the battery connection is made, both on the bottom and top of the strut bar mount, and the paint on top of the shock tower.

 

[fastasleep]

Today I ground the paint off the strut bar on either side, and ground the strut tower as best I could. I didn't want to grind off the threads of the strut top, so I wasn't able to be as precise with the electric grinding brush.

It didn't seem to improve the voltage down-spikes.

 

[14u2nV]

what is your problem? Mine is grounded there as well, with no issues. It could just be one of your engine/chassis grounds, bad positive connection or something like that. I wouldn't go running another wire to the front just yet. Check your voltage at your battery, then check it at the front of the car at the fusebox/chassis.

 

[fastasleep]

I've got two different electrical symptoms going on:

1) Recently when I've gone to start my car it won't start turning over at first. I hear the fuel pump and relays clicking and everything sounds right, but it won't start. If I take the keys out and try it again a few times and pray, then it'll turn over and start right up. Starter on it's way out?

^ This has gotten a little better some since the weather has gotten slightly warmer, but I'm not entirely convinced it's just the cold.

2) It's also becoming more frequent that when I hit the brake pedal I will watch my voltage gauge and it will spike down from 14 to 12.5 or so, for half a second, just long enough to cause my head unit to die and restart; lights dim for a sec, etc. It's mega-annoying because it interrupts whatever audio I'm listening to every time I brake...

My alt and battery are good. Where should I start troubleshooting? Starter? Relays? Bad gauge wiring? turbo timer wiring? batt relocation wiring? fp rewire wiring? The draw from the brake lights is what really triggers it.

 

[Rausch]

I would say that a part of the voltage problem could very likely be the wiring itself. These things are getting older, and old rough wiring tends to have a higher resistance. I rewired a few things in the car, here and there, and actually noticed that the flickering when braking/etc., was not as dramatic.

I would start with the alternator wiring, and maybe make sure you have solid grounds throughout, especially in the back near the battery. If the metal is rough throughout, you may have grounding issues no matter how well the ground point is prepped.



And for the record:
I heart Xtant. /ubbthreads/images/graemlins/hsugh.gif

 

[fastasleep]

How do I rewire the alternator?