Atx-30 battery installed one drilled hole

[simonasaur]

I’m slowly and lazily lightening my Nsx. Being a targa, I’m not expecting too much. I recently added an atx-20 antigravity battery to my s2000, it’s been a good experience and so I decided to do the same for the nsx. Sometimes my cars sit without a charger, so the restart feature was super appealing.

Be a budget minded owner currently, I liked the idea of the $99 holder. I was an able to make it work relatively easily and thought I’d share. I already had the car on stands, so it was easy to access the 4 12mm bolts from below the battery tray.

 

[simonasaur]

Removing the tray, you can see the two rear holes. They go all the way through and make one of the two attachments I used.
That third hole took approximately 15 second to drill.

The supplied bolts went right through to their lock washers. The closer one is actually in between the two layers of the existing tray. If you wanted to lighten it further, one could remove the upper section of the tray, but I just left it.

 

[simonasaur]

I used a bit of loctite and presto, done!

I mounted the whole shebang from below the car. Feels about as solid as it need to be. I have let the battery “die” before when it was in the car. Totally flat. Then by pressing the restart button, it fired right up with no hesitation. I recommend this battery based on my experience so far.




Took the car for a rip after. EnJoy

 

[Wild Turkey]

That is a brilliant way to mount that bracket and it looks awesome! I'm thinking of this when my battery needs replacement. I wonder what that holder weighs, as anti-gravity doesn't give a weight, odd considering that weight loss is the main thing they're selling. Looks light, <1 lb?

Specifically, I wonder how much lighter the ATX-30, 2 battery adapters, and the antigravity holder is, compared the 51R-24-RS (Zanardi) and stock holder which would drop right in. (I posted the .stl to 3D print a holder for the 51R battery that weighs about nothing in the DIY forum.) But the ATX-30 & this mount would save ~$200.

Considering that our spare tires are all dated-expired and the size of these new batteries, maybe it's time for someone to make a frunk option for the NSX1! (kinda warm though.)

Lastly, Is the battery/spare tire tray structural, or could the entire tray be replaced by a C-channel (transverse or longitudinal) that the $99 holder bolted to?

 

[simonasaur]

These are good questions. The tie down and ties from the stock holder weigh about the same as the new holder I think. So it’s probably a wash on that weight. If I had to guess, even though it’s relatively thin, there’s structural rigidity in the tray…

 

[klmken]

Will the ATX batteries charge right off the stock alternator? I've been looking around and haven't been able to find an answer.

 

[JasoNSX]

Will the ATX batteries charge right off the stock alternator? I've been looking around and haven't been able to find an answer.

Yes, the stock alternator will charge the ATX batteries. I've had the ATX-20 installed for a year now, and no problems so far.

 

[Honcho]

Lastly, Is the battery/spare tire tray structural, or could the entire tray be replaced by a C-channel (transverse or longitudinal) that the $99 holder bolted to?

Based on the bolts used and the torque specs, it likely is a secondary structural component. Honda refers to it as a "cross-member." The primary structure comprises the frame rails and the front suspension beam/subframe, but the tray likely works to help tie the front beam to the radiator support.

 

[Wild Turkey]

Yes, the stock alternator will charge the ATX batteries. I've had the ATX-20 installed for a year now, and no problems so far.

I was leaning towards the ATX-30, but if a lot of folks have done fine with the ATX-20, maybe that's all I need. It's more the $100 than the 2 lbs. But would the 30 last any longer? My reading of the Antigravity site didn't really give me the answer, other than that they don't officially recommend the motorcycle (ATX) batteries for the NSX (but they seem to work). My car does sit for the winter, so I'd need an external charger. I think my battery is on it's last legs. I'll get it checked at the battery store - if it passes this spring, I'm sure it will need replacing Spring 2025.

 

[JasoNSX]

I was leaning towards the ATX-30, but if a lot of folks have done fine with the ATX-20, maybe that's all I need. It's more the $100 than the 2 lbs. But would the 30 last any longer? My reading of the Antigravity site didn't really give me the answer, other than that they don't officially recommend the motorcycle (ATX) batteries for the NSX (but they seem to work). My car does sit for the winter, so I'd need an external charger. I think my battery is on it's last legs. I'll get it checked at the battery store - if it passes this spring, I'm sure it will need replacing Spring 2025.

When comparing the two, the ATX-30 has a higher amp-hour capacity. The ATX-30 will take longer to discharge to below 12V, if I'm understanding what you mean by last longer. I just hope that the ATX batteries will have a longer life/replacement interval than the typical lead acid battery.

 

[Wild Turkey]

I meant last longer in terms of years of service/replacement interval since, with more than 50% higher capacity, a smaller percentage of its capacity will be used each time the car is started, & batteries have so many charge/discharge cycles built into them.

 

[Wild Turkey]

Based on the bolts used and the torque specs, it likely is a secondary structural component. Honda refers to it as a "cross-member." The primary structure comprises the frame rails and the front suspension beam/subframe, but the tray likely works to help tie the front beam to the radiator support.

I can't find the reference to crossmember, just "battery holder" and "spare tire holder" in my SM. Interestingly, there are two different designs for the battery tray, a 2-rail (with a plate on top) from the body, to the subframe, to the radiator support, the other just a drawn plate from the subframe to the radiator support. I would assume the 2-rail came first, because the shorter tray requires a small beam ("Under cover set plate", p 20-72) where the 2-rail attaches to the body, to provide the front midline screw attachment point for the floor under cover.

@simonasaur 's NSX has the shorter battery holder. Based on my scanning of BAT auctions, it appears the new shorter (and thinner) tray debuted in 1997, presumably to deal with the larger spare tire (to clear the larger front brakes). My 1997 SM shows both styles of battery tray in different locations, complete with different torque specs for the bolts. I'm going to look into this further.

 

[Honcho]

The 91-96 use the "ladder" version with the rails. 97+ use the plate. If you look at the cross section of the rails, they are similar to the NSX-R chassis brace bars. It may be that, like deleting the rear strut brace on the coupes, Honda decided that the extra rigidity of the 97+ body meant the rails were no longer necessary and they switched to the plate.

 

[BrakeExpert]

Nice job

 

[simonasaur]

Thanks for the comments. I got my 1997 on bat @Honcho. My car has gps alarm stuff that draws it down rather quickly. Possibly something else as well. So far I’ve used the restart feature with success every time. Once I had my s2000 with an atx20 out in the snow for long enough for the restart not to work. I connected a lithium specific charger and it started the next day. So far so good: I’ll update if anything new presents itself.
Sam

 

[Wild Turkey]

Sorry to hear that you're selling/sold the NSX. For lighter and cheaper mount, that also does not require any holes drilled:

Save another pound: Ultra lightweight AntiGravity battery mount (or other LiFePO4)

For battery weight, it's probably fair to consider the weight of the battery holder as well. I decided to design my own ultralight battery mount for my AntiGravity ATX-30RS, like my previously posted PET-G battery bar for the 51R (Zanardi) battery, which saves an additional lb over the 9 lb...

www.nsxprime.com