Put a golf cart battery in my 5.0, saved 24lbs for $70

[SlowJim]

Hey fellow corner carvers,

Just wanted to share my experience as I don't see much talk of lightweight batteries around here. Thanks to this thread I decided to finally get around to installing my old Deka ETX9 7lb battery from my old Miata, which had been sitting in my basement on a trickle charger for a year. My car is a daily driver, so for now I've got my stock battery sitting in the trunk just in case. No permanent modifications needed other than a little trimming of the battery tray and drilling a hole in the nylon battery strap. If it dies I can swap my OEM battery back in with an 8mm ratchet in about 5 minutes.

Installed pic

From @s8v4o 's thread:

Hump that needs trimmed

After about 5 minutes of Dremel work

Stick something in the gap to make a flat "floor" for the new battery

Drill an extra hole in the strap

Test fit

All set

On mine I had to trim out the corner of the tray near the positive side of the battery because the ETX9 is very short and the wiring leading to my positive terminal was extremely stiff and did not want to bend down. However if you go with a taller battery like an Odyssey PC680 or Deka ETX15 you shouldn't have to do this.
$70 Deka ETX9: http://www.batterymart.com/c-big-crank-batteries.html

$15 Screw-in post: http://www.amazon.com/XS-Power-586-...27637321&sr=1-2&keywords=odyssey+sae+terminal

 

[Count]

Tiny...

 

[SlowJim]

Starts right up no problem. It's been in for about a week and I haven't had a need to trickle charge.

 

[SlowJim]

3 week update, I have been driving the car 5-6 days a week and it hasn't failed to start once. Probably helps that my car doesn't have any of the GT Premium audio/navigation stuff since it's just a base model. I think driving it daily also means the alternator recharges the battery and doesn't give it a chance to run down when parked. Overall very happy with my little weight reduction mod.

 

[Brezick]

Nice, still would be hesitant for DD, but would be a nice swap in at the track.

 

[weather man]

Nice, still would be hesitant for DD, but would be a nice swap in at the track.

Agree, you could even set the spare next to the tools and such.

 

[fdjizm]

Yep thems is my pics, I iz pioneer in this bitch.
The little baby battery works great, I was at island raceway all day with it (2hour drive to get there also) can't even remember the number of times I turned the car off and back on but it was fine.
I opted for the etx14 though.

 

[SlowJim]

Little update on this mod... the Deka ETX9 was causing my traction control to do strange stuff. Started turning itself back on halfway through my autocross runs and then throwing the Advancetrac dummy light. I am guessing it wasn't providing enough voltage or something. Will need to try a bigger battery like PC680

 

[CobraRed]

If people are worried about being stranded with the small battery, you only need this lithium jumpstarter in your glovebox. 1.1lbs with the jumper cables, holds a charge for 3-6 months.

Amazon.com: Astro Pneumatic 7775 12V Portable Power Supply and Emergency Jump Starter Kit: Home Improvement@@AMEPARAM@@http://ecx.images-amazon.com/images/I/416KBIaGzoL.@@AMEPARAM@@416KBIaGzoL

 

[foolio2k4]

Good until it gets colder. Had a PC680 and worked no problem for a while, but once the battery starts to degrade, it takes longer to crank and start up in cold weather.

 

[fdjizm]

I drove 2 hours to island drag way, lost track of how many times I started the car etc... little battery did pretty good. never a slow crank the whole day...

 

[CobraRed]

Good until it gets colder. Had a PC680 and worked no problem for a while, but once the battery starts to degrade, it takes longer to crank and start up in cold weather.

In LA area?

 

[Mark Aubele]

Little update on this mod... the Deka ETX9 was causing my traction control to do strange stuff. Started turning itself back on halfway through my autocross runs and then throwing the Advancetrac dummy light. I am guessing it wasn't providing enough voltage or something. Will need to try a bigger battery like PC680

I have had this issue on track with the stock battery. Ended up just having it shut off in the tune, no more issues. Only happened under extreme situations at high speed (got sideways at 110 mph), never turned itself back on under autocross situations no matter how sideways I got.

 

[SlowJim]

Interesting. Going back to the stock battery seemed to solve my issue

 

[2013MustangGT]

My car is not a DD. I used a PC 680 because it can sit inside the car at full charge and I don't need to put it on a battery tender. For this application you want the PC 680 to be at 13.50 volts to be at full charge. I don't have any traction control so that will never be a problem for me. Also, Terry @ Vorshlag runs one in his shop Mustang and he has all of the navigation, sat radio and whatever else came with the car and his PC 680 works fine.

On a side note I used two PC 680s for my winch instead of a 100lbs marine battery. The weight of the two PC 680 is only 28lbs. I just make sure after using the batteries that i fully charge them before storing the trailer. Before I go any where I put a volt meter on them to see if they are still holding the charge. So far so good.

 

[SlowJim]

I am beginning to think the issues I was having were heat-related. Apparently AGM batteries are very heat sensitive and I removed the battery insulator because it did not fit my smaller battery. I will try some DEI heat reflector on it and report back.

 

[oldVOR]

SlowJim, how has your battery project been progressing?
I'm in the market for a replacement and curious to get an update on how the battery has been working.

 

[SlowJim]

Well for some mysterious reason, my advance trac kept coming back on in the middle of autocross runs so I took it out. Can't say with certainty it was due to the battery, but it definitely seemed to happen more with the deka.

The good news is, the car never once died on me or failed to start. Pretty amazing given how tiny this battery is.

 

[Pentalab]

I would have thought that a golf cart battery, which is a deep discharge type, would not be suitable for use as a start battery ?

 

[SlowJim]

My previous car was a Miata. People used them all the time. I used this same battery (Deka ETX9) on that car and it didn't work out well. The car had some kind of drain so it would die if parked more than about 2-3 days. Never had that issue with the Mustang though. Started right up every time.