battery internal short

A simple battery check with a load tester from say auto zone or similar will tell you if the battery is good or not.

If one of the internal lead plates is shorted out they will be able to determine it by testing it.

Don't replace it just due to old age. Due to the battery is always on a tender there's a chance it is still good.

The main damage to batteries happens when the lead plates inside get sulfated. Sulfation occurs when the volts drop below a certain level, I believe below 12.2 V but would need to verify. So if your battery dies etc., sulfation begins and persists til the necessary voltage is returned.

Batteries can still be useable with minor sulfation. At the point where the sulfation is too much the battery will not be able to charge up to the neccesary voltage and becomes unusable.

Many maintainers have a desulfation cycle that helps to remove minor sulfation.

This being said, if the battery has been maintained at the proper voltage there is a decent chance that it is still good and the problem lies elsewhere.

 

The Optima batteries lose a cell and produce low or no voltage when they fail.
I have had great luck with Optima Red Tops that were made in Colorado.
The new ones coming out of China are garbage. I went through three in my 355 in 14 moths before going to another AGM battery. I averaged 7 years on the Red Tops, and just got 12 years out of a Yellow Top in my work truck. That was with the Colorado, USA built Optimas.

Try another brand AGM battery, and avoid a new Chinese Optima.
Just my experience, yours may be different.
Good Luck!

Cheers,
Marc

 

A bad ground is always a possibility, but I would bet on a bad battery.
It could be loosing a cell intermittently and causing your problem if it goes open.
What is the output voltage on your "Orange Top"?

 

Here is what I went with in my 355.

Duralast Platinum/Battery (34R-AGM) | AutoZone.com

 

In my experience, a short circuit within the battery is an unrecoverable failure, not an on / off thing.

 

If the battery shorts internally you are correct that it is a hard failure.
The Optimas can have intermittent connections between the six AGM cells that make up the battery, or a dying cell.

 

Many years ago in prepping our Miata Chump Car for racing I installed an electrical cut out switch on the rear fender that disconnected the battery negative from the car when switched. When on everything lights up, when off everything goes dark. Imagine my surprise when I failed tech inspection because removing battery ground would not affect the engine running at all. Total rookie move that I didn't test that it would actually kill the engine as required by the rules, but the alternator had no issues running the car with no battery at all. I had to install a second switch mighty quick to disconnect the alternator to kill everything.

Although a Miata isn't a Ferrari, I don't think it is a negative battery terminal issue. It could be an internal short, but not the loose terminal.

 

I'm not so sure disconnecting the battery when your car is running just to satisfy your curiosity (or worse yet, the curious people on this forum) is such a good idea.

I'm no alternator guru, but I can imagine the control circuitry associated with the alternator would be at least surprised and perhaps irritated enough to catastrophically fail just to teach you a lesson. Call me a chicken if you wish.

However, if you do some experimenting with a disconnected battery while the car is running, please report back with the details and the cost (if any) to put things right.

 

Had a tr in the shop with this problem a couple yrs back, the issue was the fuse box. The mondial and TR share a similar type of multilayer board, it unfortunatly falls apart, catches fire in some cases and mostly shorts out. No replacements to my knowledge, some can be repaired. Others bypassed with external circuits. I would start by checking the box and its connections, along with the fuses and relays.

 

+1

Same as on 328. The power for the entire car comes from the battery via two thick red wires which run to a large black connector which plugs onto the fuseboard and distributes power to everything via the internal layers of the PCB. Probably something in this area.

Its unlikely be the battery if it fails when driving because the alternator should run the car. If the battery had developed a short serious enough to cause the car to lose power this would be obvious, the battery would be smoking.

Note about disconnecting the battery when the car is running: Dont. Although the alternator power will run the cars systems, it will not have the smoothing effect of the battery and will be a raw fluctuating voltage and probably higher than it should be, with a possibility of damage to the cars systems.

 

Maybe -- if that added connection is in the two large red wires that go to the K connector -- is it? Or is it just a connection in a +12V source going to the added Helms' relays? I. e., Do you still have the stock two large red wires going (uninteruptted) from the +12V battery terminal to the K connector? Those would be another suspect to investigate IMO -- both at the battery end and the fuse-relay panel end (if the trouble isn't an ancient battery ).

 

And what about at the battery end for the two large red wires?

(Losing +12V on the added red wire going to the Helms' relays wouldn't kill the engine, lights, etc.)

 

I don't THINK it would be an issue to disconnect the battery, but I wouldn't try it just for fun even with your car. I'm with you.

 

Those are exactly the strange symptoms I had on my Celica GT-Four for a few months, until I went around a corner and it died flat -- no lights, no nothing.
The flatbed truck operator informed me that the "roast beef smell" was the battery melting.
The Die-Hard had melted internally, and, on that last corner, all the plates collapsed.
(Apparently, they'd been loose for a while.)
But then, the battery on that car was about six inches from a glowing turbo.

I had a different Die-Hard last 13 years in the Alfa --
-- but the Alfa's battery is in the trunk, away from heat, and there isn't even a clock: when it's off, it's *off*.


I played about with a Red Top in the 328 for a while, but it didn't like taking the winter off. One of the cells died, and the battery dropped to 10v.

I find my best experiences lately are with $50 mundane Interstate batteries from just about any shop in town.