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Hi everyone

I learned that our battery is very heavy compare to Miatas from good win, and wonder if we could relocated it to the trunk with a lighter battery?
 

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why would you want to relocate it to the trunk? if you are looking for a lighter battery, there are kits for lightweight batteries. also you may check the specs of a miata battery. but remember there is a coolant pump which continues to operate after the engine is turned off. although the battery is heavy, I would not consider replacement until it fails. the layman will not notice the difference in weight during their driving experiences, and the differences are primarily going to be appreciated on a car which is regularly tracked or is primarily used for racing purposes
 

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Anything is possible...but in this case, what would be the purpose? What do you want to achieve? As noted, Good-Win have the light battery install, if that's what is needed. Would moving it (light battery or otherwise) achieve anything?
 

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Relocating a battery to the trunk is no easy matter if you want to do it right. It was an enormous amount of work for my dad in his 1970 Nova, I wouldn't even consider doing it on a modern car.
 

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Not easy to pass 2 3awg gage wires from front to back, then you need to fasten that battery. The advantage is it would add some weight in the back. Beside that, I would pass on into another mod.
 

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By the time you run the cables to the trunk you are better off just doing our light battery setup....which saved us over 30 pounds on our Fiat 124's front end. Our thread with lots of weight saving details HERE.

STOCK


Ours:



If I was building one of these from scratch as dedicated race car, including custom harness, then we would put it passenger side trunk for best weight balance of driver's weight...but outside of such a balls to the wall race application is makes no sense to do. I say that having done it before, so I understand all too well what is involved in doing it right. Our NCLIGHT time attack NC Miata below had a wet weight of driver's corner at only 524 pounds...and that generation was a bigger chassis than current Miata/Fiat. We even put the oil sump in the trunk, dry sump engine setup as part of the effort to better balance with driver's weight. Fiat's turbo location makes driver's front corner extra heavy, use of the flooded battery is crazy. Fiat 124 even with our light battery is wet weight at driver's corner of about 150 more than that project below, and about 100 pounds more than current ND Miata driver's front corner (I just posted the ND Miata vs Fiat 124 corner weights in our thread here the other day).

 

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Brian is right. While it would improve the weight balance to move the really heavy stock battery to the trunk, the advantage is negated by the added weight of the cable and required hardware to make it a safe install. Our Project Midnight, a '09 Dodge Challenger, actually has a trunk-mounted battery from the factory. I honestly think it's more of a gimmick, because it's an "old racer's trick" than an actual improvement. When the OE battery gets old, you could easily shop around for one with the correct terminal placement that's a little lighter, or go all-out with the lithium battery if you're serious about racing.

My plan for our car, since it is regularly used for autocross, is to swap in a lightweight Li-poly battery in the OE location, with a Pb-acid powersports battery trunk-mounted and given access to B+ power (power when the key is at least in acc position), which will be made easy to remove for race events. Using both means no heavy gauge wiring to the back, since the trunk-mounted one is only there as a "helper" for every day driving and for when the car sits for a few days without being driven. The only time the car will be running on the Li-poly alone is during a race. I have experience with batteries and battery mounting, so I've got a pretty good idea of where it'll go. It's just a little ways down on the to-do list, since the stock battery is holding up fine, and we have a laundry list of mods to get to ;)
 

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i agree with the other comments in that a true battery relocation to the trunk is best suited to a serious autox or track car.
As a compromise, and something that was virtually free,...I needed a new battery for one of my other cars and was all set to shell out the $100 or so. Then I noticed that the fiat battery was about the same size and had the terminals in the right place. So I used the $100 that I had budgeted for the replacement battery, and bought a new group 51R battery for the 124. The group 51R has the terminals in the correct layout and fits with the stock 124 battery bracket.
The pluses are it is 11 pounds lighter than the fiat battery and with the smaller pushed over the one side of the tray, I can access the oil filter even with my EC intake installed.

Then I threw the still good fiat battery into my beater.

And before people start chiming in about cold cranking amps and amp-hour capacity, let me just say that I am an electrical Engineer and I have assured myself that the group 51R battery will work fine for my daily driven car in our comfortable pacific northwest climate.,,,even with the turbo coolant pump.:D
 

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Mark 2 (NB) Mazda MX-5s used to have the battery in the trunk as standard.
However I distinctly remember that because of this location it had to be a gel battery and not a wet battery. So that there was no spillage of acid in a confined space. I think it also has a rubber pipe that vents to the outside.
If you look up photographs of where people had used wet batteries in trunks, you can see where the acid has corroded the surrounding area.
 

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Mark 2 (NB) Mazda MX-5s used to have the battery in the trunk as standard.
However I distinctly remember that because of this location it had to be a gel battery and not a wet battery. So that there was no spillage of acid in a confined space. I think it also has a rubber pipe that vents to the outside.
If you look up photographs of where people had used wet batteries in trunks, you can see where the acid has corroded the surrounding area.
Yes, a wet battery in the trunk, or under the rear seat, German style, or MGB style MUST be vented to the outside. Didn't the old 124 have a rear mounted battery? I remember vent tubes hanging down near the rear diff.
 

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i agree with the other comments in that a true battery relocation to the trunk is best suited to a serious autox or track car.
As a compromise, and something that was virtually free,...I needed a new battery for one of my other cars and was all set to shell out the $100 or so. Then I noticed that the fiat battery was about the same size and had the terminals in the right place. So I used the $100 that I had budgeted for the replacement battery, and bought a new group 51R battery for the 124. The group 51R has the terminals in the correct layout and fits with the stock 124 battery bracket.
The pluses are it is 11 pounds lighter than the fiat battery and with the smaller pushed over the one side of the tray, I can access the oil filter even with my EC intake installed.

Then I threw the still good fiat battery into my beater.

And before people start chiming in about cold cranking amps and amp-hour capacity, let me just say that I am an electrical Engineer and I have assured myself that the group 51R battery will work fine for my daily driven car in our comfortable pacific northwest climate.,,,even with the turbo coolant pump.:D
Do have a photo of your set-up?
 

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Mark 2 (NB) Mazda MX-5s used to have the battery in the trunk as standard.
However I distinctly remember that because of this location it had to be a gel battery and not a wet battery. So that there was no spillage of acid in a confined space. I think it also has a rubber pipe that vents to the outside.
If you look up photographs of where people had used wet batteries in trunks, you can see where the acid has corroded the surrounding area.
Wow that's crazy. My Hemis have the battery in the trunk. I recently installed an AGM in my Challenger, and when it's time to replace the one in my Charger it will also get an AGM.
 

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my NB has the battery in the trunk, and also my alfa romeo spider had a battery in the trunk. for the nb the battery has not caused any problems, but other than a bit better balance I really don't see any reason for this. with the longer battery cables, it appears like the battery is always weak. the windows are slow to raise and lower, and at times the headlights dim slightly as the rpm's drop below 1200. I understand the battery is 17 years old, but it still cranks the car. on the alfa, the battery was an old lead acid type, which over time corroded it's way through some of the sheet metal of the trunk. also with the alfa, if there was less than a full charge, she was not cranking. even though it may seem to be a cool mod to do to a car, and a bit more access beneath the hood is always welcome. unless the use of one of these vehicles is strictly for track use, battery relocation is only going to become a performance impediment, with the advantage being nothing more than a conversation piece......
 

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When my dad relocated his battery to the trunk in his 1970 Nova, he used appropriate gauge wire (can't remember what size), and an appropriate alternator and wiring scheme so that the battery ONLY powers the starter at startup time, while the alternator runs the electrical on the car. When running, the battery is not powering anything, and is only being charged by the alternator. When it's done, it needs to be done right.
 

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Looks good, what brand did you use?
I am not proud,...Costco. I find their batteries to be of consistently good quality, usually a fresh date stamp, and good value for the price.
 
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I am not proud,...Costco. I find their batteries to be of consistently good quality, usually a fresh date stamp, and good value for the price.
That battery is quite a bit smaller! and 10 pounds lighter. Good to know it otherwise fits good.

The MX-5 battery is 1 pound lighter than your new battery, but probably costs a good chunk more.
 
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