Dead battery. Bulging sides. Non-Optima. Size 48.

[sugarwood]

First, I would like to replace the battery hold down allen bolts.
Anyone know the part number? Not seeing it in the PET


Went to start the 911 and the battery was dead.
I haven't driven it much, and it's cold, so I figured it just drained.

Well, I've had the car for 2.5 years, and do not know when the battery was replaced by PO. I thought maybe I should just buy a new one?

Well, I'll recharge it while I think about it. I have a 10A recharger, but decided to recharge the battery outside of the car, in case it explodes. As I pulled the dead battery from the car, I noticed the sides were slightly bulging.

I was on the fence about replacing it, but now, screw it, $125 is not worth breaking down or having an exploded battery that is at least 3 years old, and likely older.

Dead battery.
Old battery.
Bulging sides.

The current battery is AC Delco 48-6YR.
Can you suggest a direct replacement battery?
I don't want to make any battery tray mods, and don't want a fishing boat battery.

[sugarwood]

Can someone post a photo of their hex head battery clamp bolts?
Just curious if they are that golden color like many bolts, or if they are black.

[RedCoupe]

My 86 had a quite new battery, one of the gigantic types that fills up the entire space between the inner fender and the front A/C condenser blower. Trouble was, it had a very slight drain that would discharge the battery when the car wasn't driven for an extended time. My 1990 964 is apart for extended work, so I took its battery and put it in the 1986. The bracket fits perfectly, but uses another set of holes for the hold down bolt. This gives plenty of room for a battery mounted shut off switch which completely solves the discharge problem. I'm at work so I don't have the battery group numbers, but when I looked into this a while back I found that the smaller 964 battery is actually listed in some battery books as an optional size for the 84-89 Carreras. Switching to the smaller battery does save some weight as well!

[JRSIII]

I can't post photo as I only have access to mobile device right now. However, on my 88, the battery terminal clamp bolts are not hex head. On the positive terminal, there is an all thread stud with hex nuts on either side. On the negative terminal, there is a square head bolt with a hex nut on the opposite side. They are neither yellow cad plated nor are they black. They are silver, same color as the clamps. If these are not the bolts you are asking about then my apologies.

[sugarwood]

They are M8x1.25 and have a recessed Allen key that holds down the battery clamp thing.

[Taxi!]

Sugarwood,

My battery clamp and bolt from my '86 are pretty rusty but I took them out of the car when I recently relocated the battery to the smuggler's box so here's a picture. The clamp definitely looks like it was black at one time, and you'll notice the bolt isn't a hex head but an allen head. However, the PO(s) did a lot of sketchy stuff to this car so I can't swear that either part is OEM. Hope this helps.

Jeff

[JRSIII]

My bad. On my 88, that bolt is definitely yellow cad plated. As is the washer.

[sugarwood]

[sugarwood]

How do you know when this is charged?

[sugarwood]

Sorry, I was using hex head and allen head interchangeably.
It's allen head.

[sugarwood]

Any mainstream battery suggestions?
Just get size 48?

[Tremelune]

You can use anything that will physically fit, for the most part. They're all made by the same 2-3 companies. I have an AGM Odyssey PC925 just strapped into place. If I wanted to use the standard bracket, I'd just buy any big ol' lead acid battery that fit at my local parts store.

The very intelligent Battery Tender Jr is $25. Ain't much reason not to just have one always sitting on every vehicle that isn't driven regularly.

The last battery I pulled out of a car went 9 years. Nothing special about it, it just saw an easy life.

[msterling]

I used a smaller. lighter maintenance free battery and mounted it on a tray I made from a plastic cutting board. The board mounts to the original clamps. The hex head bolt and clamp were yellow plated on my 1988 Carrera.

The charge indicator should taper down to an amp or two when/if the battery is fully charged. The battery would have to be load tested to see if it is healthy. A bulging battery could have been cooked by a malfunctioning voltage regulator in the car or a powerful charger left on "boost" for too long. Some batteries just have crappy cases that bulge as they age (kinda like people).

BTW, a common cause for a dead battery is the door switch. It can leave the window relay active if the switch is stuck. To test, shut of the engine, open door, close door then see if windows still work. If they do then the switch is malfunctioning.

[darrin]

Originally Posted by sugarwood

Any mainstream battery suggestions?
Just get size 48?

Sugarwood -- our carreras came from the factory with a group 49 battery, which is slightly larger (front to back) than the group 48 sized battery you appear to have -- there should be a predrilled hole in the battery tray farther to the front of the car than that used for the group 48 battery that's supposed to hold down the group 49.

I downsized from a group 49 to group 48 battery a few years ago and have not noticed any issues -- I also bought (and strongly recommend) an AGM (advanced glass mat) style battery, which uses technology similar to the optimas to "contain" the sulphuric acid so that it doesn't spill/leak.

Bulging sides of battery -- could be indicative over overcharging? Do you monitor your voltage using a voltmeter -- failing voltage regulator could screw up new battery too?

[sugarwood]

Yes, I have 2 bracket holes. The 48 uses the smaller one. 49 seems gigantic, so I prefer to stick with size 48. Prefer not to have a 49 crammed into the space.

I will test the door switch. I've noticed my cabin light not coming on when I open the door, sometimes.

How do I verify my voltage regulator?
Just stick the alternator onto the battery while running?
Normal charge is like 14V, right? Anything much higher means a problem?

[sugarwood]

Wow, a little sticker shock.
Batteries used to basically be $100, and $125 for the top shelf one.

Now, they're all $175 and up.

[sugarwood]

Funny, the PET actually specifies a hex head bolt.
Part number 99907503202. p.434

[Rawknees'Turbo]

Woody, if you use a battery charger that doesn't have a volt meter built in (the one in the pic has an amp meter), or a "green light" that indicates full charge, you have to use a multimeter to verify battery voltage. A full charge, with regard to using a battery charger (not regarding resting battery voltage of an installed battery) is 14-14.5 volts. If you charge beyond that, you potentially damage the battery. By the way, you measure with the charger off - turn it off, and wait a few second for it to settle before measuring voltage.

To test the alternator's voltage output, use a multimeter and measure the running voltage at the battery (running as in "engine running") - 14v would be considered perfect (cold alternator, no accessories on, etc), but anything in the range of 12.5-14.5 is good (I even see barely above 12v sometimes at idle, with the engine hot, all accessories on - including my additional a/c condenser fans - not a problem as it goes right up with a little additional RPM). Test at idle and at around 2000rpm - output will be higher at higher RPM. The measured output is affected by heat, what accessories are on, resistance in the primary wires, state of charge in battery, etc., that is the reason for the "acceptable range".

You can also measure running voltage at a hot source in the engine bay, such as the rear fuse panel, but that number will be a little higher than what you see at the battery.

[sugarwood]

I'm still wondering how to read that gauge on the charger.
Why is the charge 100% in the middle of the gauge??
Why are there 2 units on the same axis.
If it's at 100%, the lower number is about 5.
How can the needle go below 5, in that case?
You can not go past 100%

[Rawknees'Turbo]

^^^

I don't know what to make of that charger gauge either - am not familiar with how to use an amp meter to judge battery charge condition.


Edit - ok, looking at the gauge again, it appears that the bottom scale are amps and the top scale indicates "how charged" the battery is - so the more discharged the battery is, the more amps will be sent by the charger into the battery. And you can indeed go beyond 100% charge - more than 14.5 volts would be beyond full charge (aka - overcharged).