Battery relocation benefit in NA?
 

Tried looking around, but posts i find about battery relocation tend to do with FI applications.

Im wondering if relocating the battery is worth it to a NA application(with cai to increase space).

In race trim i would think every bit of cooling is essential, but what about a rx8 that sees the occasional autox/track and one that is daily'd.

Can anybody chime in?

If you do any track, then I would say it's beneficial to relocate, but not necessary.
But, if it's just for a DD, then it's a preference.

It will put about 40lbs or more to the rear ..passenger corner is ideal.

So it helps weight distribution.

With the added weight of the wire..unless you go to a smaller battery your net weight will go up...but with better balance

Main benefit is to have more room in engine bay and swap to a less weight battery.
If you have vented hood, it'll help out cooling once you relocate the battery.
That's about it.

One thing that nobody mentioned is that it's way healthier for the battery to be inside the car. Being in the heat under the hood shortens their life.

Plus better cooling since the air coming off the radiator has somewhere to go and better weight distribution.

if you track the car, don't forget you need to also have a cutoff switch.

An easy "half-way" alternative is to use an Odyssey 925 MJT battery in the stock location. It will open up some flow area behind the radiator (though not as much as an AEM/Mazdaspeed CAI) and saves ~25 lbs of deadweight on the nose. It's quite a high-tech lil thing (check Odyssey's website) and easily shipped from Summit Racing since there's no liquid in it. I've changed my install since this pic, putting big holes in the front part of the battery tray and a piece of plastic (ex-kitchen cutting board) on top to hold more securely since it's narrower then the stock battery as well. Personally, I did not want to add weight with extra wire for a rear mount, then compensate the weight by using a battery that was marginally-sized for use as a DD, especially considering the increased voltage drop to the starter from the long wires.

This looks like what i might end up doing, is this battery capable of DD duty? I daily my car and it might see 1 track per year.

I would ideally like to move it to the trunk, but it is a daily so problems may arise with the longer wire like you said, also there might be a risk of a cabin fire, i think it becomes too much of a hassle.

this subject has all been run into the ground previously, including why you should not install an Odyssey battery in the engine bay

:mfingquadruplefacepalm:

back to square one then..

I moved mine to the trunk for better access. Without the battery in there you can access all your coolant hoses with the car running (great when checking for leaks), its easier to add grounds when installing things, and the bay just looks a bit more tidy. That and my first battery exploded all over the place and destroyed my radiator, fans, and hoses, so an optima red top in the trunk makes me feel better :)

Really? I've had mine for 2 years there with zero problems. Others, longer - https://www.rx8club.com/series-i-tech-garage-22/odyssey-pc-925-battery-experiences-189415/ (a post you responded to), but the 925 seems a relatively rare choice, so "statistics" are lacking.

Most historical verbage was on the PC680 and not at all clear whether they were of the "MJT" variety (required for underhood installation) or the normal (cheaper) unshielded one. Hardly conclusive as far as I can tell.

The subject of rear mounting per se has indeed been discussed rather endlessly, however. Race car = rear mount. Street car or little money = leave it alone. In between = no "perfect" solution. YOU (the OP) have to find your own balance.

YMMV

You mention your car as DD with *1* track day? Why bother? You'll not notice any advantage, if there even is any and changing from OEM position will degrade any effect anyway bc the extra stuff needed adds weight over the battery alone. And most all cai's fit w/battery box inplace. Moving the battery is not required.

The OEM position is bad bc of heat, but a LA battery works ok, so why not get a smaller, lighter LA for there? Cheap, easier, done, and you'll feel better. The 8 originally came with a smaller battery, but people complained when leaving the car for weeks that it went dead. But DD will keep it well charged.

An lighter Odyssey works fine there as well... for 2 yrs. Then simply get another. It's only $$, it's easy, done, and you'll feel better still (it's more *advanced*, yes). MJT version or any other typical battery insulation there is a joke. Heat soak wins easily and quickly no matter what. Put a temp probe there and prove it to yourself :).

Except 4 a race car, moving the battery from OEM location is just good in your mind (but a fun project ;)), as it adds extra weight, components, hassle, issues w/grounding, voltage drop, extra POF, etc., and does next to nothing performance-wise.

Bottom line, you'll need to get a whole lot more inventive and high tech to improve upon Mazda's KIS battery solution.

thanks everyone, since i daily my car, using a smaller battery in the stock location seems like the best thing to do.

you can do what i did. https://www.rx8club.com/do-yourself-...-fluid-216351/
i still daily it in the summer months.

i actually looked into that, i was worried the battery wouldnt last in that location, but apparently it has?

I daily the car and dont have any soundsystems or anything so i dont have to worry about it losing charge.

Spin, what about a small lightweight Braille Battery? I think they go as low as 9pounds before the amperage drops too much?

braille is an overpriced re-branded deka fyi

And it looks cool
 

https://cimg9.ibsrv.net/gimg/www.rx8...521995ed3f.jpg
:yesnod:

It's better to have it mounted forward up against the the rear seat trunk separation panel within the wheelbase ....


wth, a chain for keeping the surge tank located?!?

Please post complete pics of this car.

You forgot already? lol

https://www.rx8club.com/rx-8-multime...1/#post4635675

https://www.rx8club.com/rx-8-multime...1/#post4635920

https://www.rx8club.com/series-i-aft...3/#post4638724

Unless it's for ballast, I'm not even sure why battery relocation is a thing these days. My miata has a 2 lb lithium battery that takes up hardly any space.

lithium batteries don't like heat, especially rotary engine heat

The factory location inhibits radiator flow, which then exacerbates the noted prior situation

A 2 lb battery might cut it for a Miata, but it's begging for a rotary engine to either need a jump best case, (edit) or be flooded, or maybe even lose an engine worst case

So my 10 lb lithium battery has the cranking power and amp-hr stamina of a truck-size acid battery, but costs 20x more too

So then we go back to the first reason noted above, because the last thing you want to do to a battery that would otherwise have a long service life in the trunk and costs so much is to force it's early demise by baking it in the engine bay.

I learned all this the hard way with quite a few lesser Odyssey, Braille, etc. batteries before finally paying to do it right 7 years ago


.

Another piece of advice....don't go to a small battery that has a low reserve capacity

I lost one engine for sure...and likely 2 because the power steering and other electrical loads overwhelmed the alternator/battery and allowed my system voltage to drop enough that I had a misfire....

Forgot to add that many competition rules don't allow the battery to be in the passenger compartment either ...

I had no idea heat was such as issue for the lithium batteries. I ran one in my daily (mazda2) for about 2 years before I sold it and had no issues, though I'm sure the rotary puts out more heat than the little 1.5 mzr motor. Maybe a custom box or heat shielding would allow a lithium unit to be used sucessfully.

It may depend on your brand, but the standard Odyssey battery is only rated for 115*F and the metal jacketed version still has a maximum 177*F rating. I even killed an Odyssey PC680 jacketed version with it between the engine and the radiator. Not to mention that it simply doesn't have enough overall capacity for this application, which also decreases as temperature rises. This car has a lot of electrical demand thanks to EPS. The alternator should handle that in most situations unless you have high underdrive pulleys at OE idle etc., but it simply doesn't take much to sap one of those small, low capacity batteries. The rotary engine also needs a strong starter rotating speed to fire off quickly moreso than a piston engine.

Best deal on Group 35 battery is the Costco battery - even looks identical to the Mazda OEM I replaced. See more at:

https://www.rx8club.com/series-i-tec...stions-264356/

https://www.rx8club.com/series-i-tec...-186805/page2/

Spent a day in the garage with some steel and a welder and made my own battery relocation.

I mainly wanted to free up air flow behind the rad and move some of that dead weight back behind the struts
https://cimg7.ibsrv.net/gimg/www.rx8...0efa5975a.jpeg

https://cimg8.ibsrv.net/gimg/www.rx8...21694478a.jpeg

https://cimg9.ibsrv.net/gimg/www.rx8...e074aee57.jpeg

Lots of room for a top mount turbo now... just sayin!

Nice work, but it's heat that kills batteries and that was my main reason for relocating it to the trunk.

I put one of these in the factory box (STX30L-BS):
https://www.batterysharks.com/Sigmas...-30-385-HD.htm

Seems to work well and saves a few lbs. The battery that came with the car had the terminal locations reverse from stock design, and was larger than stock. So neither the battery box or intake box fit properly.

If removing the battery and intake boxes improves cooling significantly, I'll consider a relocation in the future (and switch to a lighter lithium unit). Has anyone done testing with water temps on track with stock setup vs relocated battery and aem intake?

No turbo, just cooling and aero for now.
If anything I want that holy grail and put an additional dorito on that motor

Heat kills batteries so yeah, and trunk mount would be nice but there’s soooo much extra work that I don’t want to do. I guess you can argue welding and fabing is just as much work but I’m more willing to do that than run a ton of extra wiring and what not.

My main concern was air flow and weight out front of the struts but maintaining factory CA/CCA is key to longevity of the battery rather than being concerned about what the heat will do to it.

i.e. 3 rotor; in that case don’t forget to buy your lottery ticket today ...

Or go to Walmart and fall while buying a watermelon. Someone got seven million that way:

https://www.google.com/amp/amp.grubstreet.com/2017/11/walmart-loses-lawsuit-to-customer-who-broke-hip-buying-watermelon.html

Seven million could buy a lot of 3 rotors. Or one of Mad Mike's 4 rotors.

Thing is, you can't go to Walmart and fall on purpose. I think there's a name for that. Oh yeah… fraud.

Considering the fraud they commit on their employees, my name for that is ... just rewards. What they do to their employees to avoid paying the any insurance etc. benefits is criminal in my book. It’d be my dream that they crash & burn and all the mom&pop hardware etc. stores they ran out of business come back. Bottom line is that they carried everything to kill the competition, then the bean counters cut out all the stuff deemed non-profitable, and now you can’t find anything any place local. Everybody just carries the same generic basic crap from Asia.

Can’t say I ever approve of insurance fraud. That said, you bring up some good points.

yeah no kidding. I'm trying lol:lol2: