Strange battery problem

[Benzito]

Running a SPF with Roush 402, not that I think that is the culprit . . .

So the Optima red top that has worked like a clock suddenly and completely dies. I mean suddenly and completely as in there is no crank, no lights, no nothing. I swap it for the newish battery in my 1968 Mustang and the Cobra runs like normal. So I figure, let me see if the dead battery works in the other car and of course, it does without any hesitation. Swap back and we're back to dead again.

The battery is getting old (Feb 2007 stamp), but I've never run into the problem that it seems to have NO draw at all.

I can't just keep the batteries swapped b/c of the size (have to get another Optima or something smaller than standard).

Thoughts? Better alternatives than the Optima (I read an old thread about Odyssey, but I have to check around to see if any local places keep them in stock).

Thanks!

Mike

[Chilibit]

Olthoff Racing puts in a standard Duralast series 56.

I changed mine over to a Braille 3121. Much smaller. Sealed. Easier to get in and out, though frankly I don't expect to do it again for 6-10 years.

I just dumped an Optima that was in a Mini Cooper. I have had no end of problems with them in trucks and the Mini in recent years. The only batteries I have ever had problems with.

[Sawdust]

Benzito
I just put a Napa 58-6 battery in my SPF last Sunday. Works perfect!

Stu.

[Got the Bug]

Did you test the output of the alternator? You might want to have the battery load tested. Five years for a battery isn't too bad.

[bobcowan]

That doesn't make any sense. A battery doesn't work well in one car, and not at all in another car. It either holds a charge or it doesn't.

Take a look at what's different between the two cars. Something is wrong with the Cobra set up, that isn't wrong with the Mustang. If you don't figure out what the problem is, it's going to happen again with the new battery.

[L79v]

I would check battery cable connections...at both ends.

[mreid]

Very strange. Ae you sure one of the cables isn't loose on the other end (frame or solenoid) and when you put the other battery in you put tension on the cable? Otherwise, doesn't make much sense.

[Benzito]

Originally Posted by bobcowan

That doesn't make any sense. A battery doesn't work well in one car, and not at all in another car. It either holds a charge or it doesn't.

Take a look at what's different between the two cars. Something is wrong with the Cobra set up, that isn't wrong with the Mustang. If you don't figure out what the problem is, it's going to happen again with the new battery.

I agree it doesn't make any sense - that's why I posted about it.

The suspect Optima battery popped right up in the Mustang. The replacement popped right up in the Cobra. When I swapped back, I cleaned the posts to be safe (although I shouldn't have had to because of what I just described in the first two sentences - bad battery works and possible bad set-up works with good battery). Also, I've had the car since October and had zero signs of a battery issue with the suspect one . . . until now.

As for the battery cables, I think it was set up for an Optima - the cables are just the right length for the Optima and I had to contort them to fit a standard battery. Again, I never even opened the battery box until last Saturday and there are no signs of any wear or breakage.

[MacGyver]

Is the Optima the same height as the other battery? The difference in size may be pulling on the cables differently. We had one at a show last year that had the cable pull out of the end where it was bolted to the frame under the trunk. Might be wise to tug and check the cables. We figured it out by using a test light from the pos terminal to the frame with the suspected battery in place and found no current to ground. Checked further and found the loose ground cable at the terminal crimp at the frame. Worth checking just incase.

[Ron61]

What MacGyver said. We had a car here that was doing almost the exact same thing and we used a volt/ohm meter to check for voltage with the battery that wouldn't work in the car and there was none. Then we put in the other battery which worked great and had voltage. It turned out that the battery cable was just out of the end terminal and when we went to the other battery which was just a little lower than the Optima, the cable would touch the end connector and work. We just got a new cable and replaced the whole cable and with new connectors and left just a little more slack in it for a taller battery.

Ron

[Tommy]

Another test for the suspect cable is to run a jumper cable from that battery post to the corresponding place where the cable goes (e.g., from negative post to engine ground). If you then get lights, you know the cable was the culprit.

Here's a second thought that probably doesn't apply to your Cobra. Modern cars with computers require a minimum battery voltage to even attempt to start the engine. It's conceivable that a weakish battery might have enough voltage to satisfy the computer in one car, but not enough to satisfy the other. Thus, you'd get a start in one car and a no start in the other. But you should get lights and accessories in both cars in this case.

[lnfletcher]

One thing to check is a broken post. It can be separated in the battery and depending on the pull of the cables, make a connection on the Mustang, but not in the Cobra.

[Benzito]

To put a proper finish to this story:

1. Remember that I stuck the Optima back in last week after it worked in my other car and the other battery worked in the Cobra.

2. One last menacing glare and curse of the car on Saturday before I break down and call a mechanic or a tow.

3. I stick my key in and there it goes, like NOTHING EVER HAPPENED. Lights work, car drives, no issues. Battery continues to peg the meter with a full charge. I am happy and I am not looking back!

4. To be safe, I took others' advice and replaced the battery-to-earth cable with an extra on hand. The end that grounds to the frame was cracked a little bit, but was still mounted and had good contact with the frame, so I'm thinking the mount wasn't (fully) the culprit. I hadn't checked it that closely before and didn't fiddle around with it in between the switch in batteries, but better safe than sorry.

I think I just have a bit of Stephen King's "Christine" DNA with my cars. Almost the same thing happened with my other British car (RR County) a few months back when it would crank and crank, but never fire. Three days after I told my wife that I hated the car and I would sell it, it starts up again. Has operated without incident ever since.

[ERA 778]

Any Lucas Electric components - switches, relays, etc. on the car??? That would explain everything!

[MacGyver]

Ooooo Lucas, the prince of darkness. That would explain everything for sure '