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Battery relocation to under car in front of fuel tank


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I've been eyeing the space I could recapture if I were to move the battery. This would involve getting a dry cell and placing it somewhere. I know it's common to move it to the trunk of the passenger compartment, but I don't like that for a few reasons:

 

  • Would require heavy-duty mounts to keep it from becoming a deadly projectile
  • Those mounts would require marring up my beautiful trunk area.
  • I don't want to lose space in the trunk area.

Looking under the car there's plenty of space for a Braille or similar battery in between the fuel tank and the mustache bar. Both passenger and driver sides have space, but I would probably take advantage of the extra shielding that the passenger side offers, as well as keeping the battery weight on the right side of the vehicle.

 

My goal is first and foremost to free up space in the engine bay so I can move what was formerly the fusible links in that corner. Any weight shifting (positive or negative) would be secondary to that.

 

To eliminate potentially dangerous sparking that would occur when messing with the terminals, I would wire in a cut-off switch in the battery tray area in the engine bay.

 

So, besides the obvious possible sparks when messing with the terminals, what other downsides are there? Road debris? Water? I don't drive in the rain, but it's not something I'd like to have to fear my car going up in flames because of. I don't see that being more than a corrosion problem due to the low voltage though.

 

My idea thus far is to make a steel frame, possibly fully enclosed on the front, to contain the battery. This would be bolted in place. The wires would be routed in the passenger compartment up to the battery tray in the engine bay. One would be connected to a battery cut-off switch. Then to the starter and fusible links as normal.

 

Alternatively, I could make a frame to hold plastic battery boxes, as I see on diesels a lot.

Edited by BLOZ UP
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Sounds fine, so long as you don't intend to race the car competitively.  For NHRA, if you relocate the battery from it's stock location, you have to have a battery shutoff switch mounted external to the car, visible and accessible from the very back of the car.  Why this isn't required for a battery in the stock location, I have no idea.  For that reason, I would go ahead and put my shutoff switch back there instead of where you were considering.  I don't know whether I would worry about having the battery right where the fuel lines are...or not...the area is well enough vented...thinking out loud.

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Ah, yes, that's a very important point I completely skipped over. I want to continue in SCCA sanctioned autocrosses. I'll have to look in the rule book. I'm in SSM, so it's just a safety concern. I'd also like to go to the drag strip, which is NHRA sanctioned IIRC.

 

Now, I have my rear bumper still attached. I was just thinking that instead of cutting up the rear body, I could place the battery cut off switch there. I hear that it's required to use the positive cable through the switch? That sounds kind of dumb.

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Seems like a lot of work for not a lot of gain.

Seconded.  If you planned to stick with a traditional lead acid battery it would make more sense to move that 40+ lbs to the rear.  But if you plan on going with a braille, the weight redistribution doesn't seem worth the trouble.  You say you have been eyeing the space you would recapture, do you have plans for the area where the battery sits now?

Edited by Namor
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My VG30ET turbo manifolds come mighty close to the fusible link area.

 

My "fusible links", boost sensor (for a gauge), fan relays, and some other items would be neater and more importantly, away from my turbo headers. I'd show you a picture but the host of all my images went 404 and the computer I have them on is 503 at the moment.

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My VG30ET turbo manifolds come mighty close to the fusible link area.

 

My "fusible links", boost sensor (for a gauge), fan relays, and some other items would be neater and more importantly, away from my turbo headers. I'd show you a picture but the host of all my images went 404 and the computer I have them on is 503 at the moment.

I personally would try to find another way but if it's something you want to do, it is definitely doable.

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I am not sure if the later cars have them, but in the earlier Z's in the trunk area right behind the wheel well there is quite a bit of space. On the passenger side it has the evap tank and fuel filler, but on the driver side it is fairly empty except for the antenna. You could also throw it behind the dash or in the passenger foot well enclosed in a box and bolted down. Would make the wiring changes very minimal. And as long as it's enclosed I think it meets safety requirements.

 

My small cell takes up about 1/3 of the space of a traditional battery. if you mount it front to back on the battery tray you can get quite a bit of room without having to deal with alternative stashing. 

Edited by seattlejester
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I am not sure if the later cars have them, but in the earlier Z's in the trunk area right behind the wheel well there is quite a bit of space. On the passenger side it has the evap tank and fuel filler, but on the driver side it is fairly empty except for the antenna. You could also throw it behind the dash or in the passenger foot well enclosed in a box and bolted down. Would make the wiring changes very minimal. And as long as it's enclosed I think it meets safety requirements.

 

My small cell takes up about 1/3 of the space of a traditional battery. if you mount it front to back on the battery tray you can get quite a bit of room without having to deal with alternative stashing. 

 

Ah, that's a good idea. I'll have to get one of these small dry cells and see what fits.

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I have a 77 without storage bins behind the seats.

Your 77 does not have storage compartments? My 77 does... You would have to cut them open slightly to fit a battery though - I tried it and it did not fit, probably need to shave about a quarter inch all the way around.

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Your 77 does not have storage compartments? My 77 does... You would have to cut them open slightly to fit a battery though - I tried it and it did not fit, probably need to shave about a quarter inch all the way around.

I'm not familiar with them that much, but I believe there's a slanted-rear 77 and a non-slanted one. Mine is slanted. I want to say the front portion, right behind the seats, doesn't come up. But I haven't checked since I put the carpet in... I could be imagining wrong.

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I used the space behind the drivers side rear wheel well.Using the smaller glass-mat battery 820cca, it fit ok after you flatten the lower lip of the deck and fender joint.I passed cables forward to the old battery space after having romoved the old tray unit.I put a cut off switch behind the passenger seat and used the firewall mounted battery studs from summit so that I could have studs in the engine compartment.I modified a battery hold down brackett for it and melded the interior plastic trim piece to cover the battery and hide it from view. You only see a bulge like the one on the pass. side for the evap.tank

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A few points.  If you lift the fiberboard deck in your '77 you'll find a well behind each seat. They are the same wells that the earlier S30's had but for some reason Datsun decided not to continue using them as storage compartments.  I redid my deck and gained those storage areas back.

I put my '77 on certified scales and it weighed 1,400 lbs on the front axle and 1,400 lbs on the rear axle with 3/4 tank of gas.  The battery also helps offset the drivers weight a bit -which is also why the engine is slightly right of centerline - to improve the left-right balance of the car.  I corner weighted mine once but forgot to write the number down.  I'm kind of a minimalist when it comes to modifications and what you are planning sounds like a huge amount of work for very little gain - if any at all. The under hood area of the Z is huge so I'm at a bit of a loss as to why you would have to move the fusible link box.  I'd do a standard fuse box swap that takes up less space if it were me and I felt a need for more space there.

Edited by Phantom
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24759bc.jpg

 

My exhaust manifolds come very close to the current fuses. That's the reason. I've put some heat reflecting tape on the side of it, but it still gets pretty warm.

 

I'm liking seattlejester's idea to mount a small battery in the same location (perpendicular to how it is now), and move the fuses next to it, all fitting within the battery tray.

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