Correct battery size and fitment of Mustang battery trays

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Correct battery size and fitment of Mustang battery trays

February 11, 2014, 11:41:59 PM

I believe our correctly sized battery is group 65, correct? The 87-93 mustangs call for a group 58, correct? Do the Mustang trays swap in without modification into our cars? Mine is cracked, and I want something in mint condition moving forward.

I'm curious because my Optima is now useless after 7 years so a new battery is needed. I'm looking at Sears' DieHard Platinum series (same as Odyssey) as a replacement AGM, since the things never corrode posts or vent gases (had fun with a Costco battery years ago - left a mess in the area). They appear to offer size 34/78 and 65. My current 34/78 Optima has always been loose in the tray, and I want something with a better fit, but if I get a "new" tray from Mustang parts, I think the group 65 one won't work.

Correct battery size and fitment of Mustang battery trays

Reply #1 – February 12, 2014, 12:12:26 AM

I have a sn-95 tray in my tbird. bolted and looks identical. not sure the year.

Correct battery size and fitment of Mustang battery trays

Reply #2 – February 12, 2014, 12:14:51 AM

I've got a Fox Mustang replacement battery tray from late model restoration in my Thunderbird. It was identical to the stock battery tray and fits a stock replacement Thunderbird battery just like the stock battery tray.

Correct battery size and fitment of Mustang battery trays

Reply #3 – February 12, 2014, 12:20:38 AM

Sounds good. I found people who say that size 65 fits in their fox Mustangs, so I'll stick with that battery and a new tray. I can't even start the car now. 12.6V off the Battery Tender, 11.4V after a couple seconds of cranking. The Optima battery is not happy.

Thanks guys!

Correct battery size and fitment of Mustang battery trays

Reply #4 – February 12, 2014, 02:47:06 AM

seems like the battery makers are migrating away from group numbers.. im seeing new numerology on these lately and i have to learn it all over again.

the UPS batteries i often deal with have a direct connection with group number to AH rate , typically the C/5 where capacity divided by 5hrs... these numbers im seeing are not making sense.. speaking to advance auto specifically.

group 65 in the GNB or Unigy or C&D world would tell mebi could discharge to 1.85vpc at the C/5 should allow me to use 13amps for one full hour.

auto batteries dont "list" thier specs like i think they should ,, they list some but most importantly is watts per cell which is a tell all sign of the plate design which is getting cheaper by the year.

one typical 12v battery i see all the time is the 12avr170FT ~aka 12v front terminal 170ah battery,, at the C/5 rate it can provide about 34a for an hour.

wow did i get off topic

Correct battery size and fitment of Mustang battery trays

Reply #5 – February 12, 2014, 04:54:02 PM

FYI this is what I bought several years ago: http://www.latemodelrestoration.com/item/LRS-10732B/87-93-Ford-Mustang-50L-Battery-Tray
Identical in every way to the stock Thunderbird piece.

Correct battery size and fitment of Mustang battery trays

Reply #6 – February 13, 2014, 01:24:26 PM

Quote from: thunderjet302;428817

FYI this is what I bought several years ago: http://www.latemodelrestoration.com/item/LRS-10732B/87-93-Ford-Mustang-50L-Battery-Tray
Identical in every way to the stock Thunderbird piece.

I don't get what the difference is from http://www.latemodelrestoration.com/item/LRS-10732K/87-93-Ford-Mustang-Battery-Tray-Kit ? Just a Ford part vs reproduction?

I got the new DieHard Platinum 65 in there last night, I need a post sleeve for the negative battery post, but even with just slight terminal contact, it fires up very quickly using my mini starter on a ~9.8:1 static compression motor. New batteries are always great, but especially one rated 200CA higher than my old tired Optima.

Correct battery size and fitment of Mustang battery trays

Reply #7 – February 14, 2014, 03:13:24 PM

Quote from: Seek;428785

12.6V off the Battery Tender, 11.4V after a couple seconds of cranking.

11,4V while cranking is an excelent result. Normal numbers are around 10 V.

Correct battery size and fitment of Mustang battery trays

Reply #8 – February 14, 2014, 03:29:03 PM

That was after cranking, not during. the battery must have lost a ton of capacity to get that low in only a few seconds.

Correct battery size and fitment of Mustang battery trays

Reply #9 – February 14, 2014, 07:13:09 PM

Yeah - I don't know what it was dropping to while cranking. The starter would barely turn for a couple seconds, then nothing. 50A charger on the car would get it to barely start if the battery started out "full". Not a problem now with the new battery. Runs great after I fixed a dumb vacuum line misconfiguration.

Last time I started the car was probably in the fall, and it started up just fine. It has had dozens of of complete drains in its life time, so it was time to put the battery down. The most annoying part is that I think I left a brass post sleeve/shim on the battery when I left it at Sears while picking up the replacement battery. I need to pick up another shim to get my negative terminal installed correctly.

Correct battery size and fitment of Mustang battery trays

Reply #10 – February 14, 2014, 08:20:06 PM

You lose about 50% capacity if the battery ever fully drains over night. generally if you catch other quick its fine. a charged battery will also be resistant to freezing, and a discharged one can actually freeze and damage the physical parts inside.

Correct battery size and fitment of Mustang battery trays

Reply #11 – February 14, 2014, 10:47:35 PM

I still have the original Bird tray in my TC and either 58 or 65 fits without issue... Over the years I've had each in it at one time or other, but prefer the smaller 58...

With the new type PMGR starters you don't need a kajillion amps of cranking power... The '93 Grand Marquis would still start when the battery was so bad it wouldn't operate the door locks...

Correct battery size and fitment of Mustang battery trays

Reply #12 – February 14, 2014, 11:18:21 PM

I had to upgrade my starter on my tbird when I swapped in the 3.8 t-5. To be honest, I really didn't notice much difference. it does sound a bit different though.

Correct battery size and fitment of Mustang battery trays

Reply #13 – February 14, 2014, 11:53:14 PM

Those newer starters are the cat's ass. I can barely wait till I can get a chance to go to the car cemetery and snag about 4 or 5 more, seeing as how I've got 2 extra cars with upcoming 5.0 conversions.

There's also a '93 Lightning sitting out in my yard. The owner wants to trade me for a Mustang....if the L had the original engine, I'd be on it snow in Pennsylvania. It's got a swapped in run of the mill 351w from a regular 1/2 ton, but everything else is there, as well as some rust. I'm not interested...