NC Miata Died. Then it came back to life. Looking for help.

I recently bought a 2010 Miata and the previous owner installed an Antigravity lithium battery. The car had been running great until yesterday. Until I was at an autocross event and 10pm and it started to rain, of course.

The car was sitting in the parking lot between run groups for about 15 minutes. I didn't leave the lights on and I'm not aware of any prasitic draw. I went to start it and it was completely dead. In fact, so dead that I couldn't even unlock the door with my keyfob and had to use the keyhole. Engine would not turn over.

Popped the hood and looked for a loose connection. Everything looked okay. 

These batteries cannot be jumped like a traditional lead-acid battery but are supposed to have a "restart function." In the dark and the rain I couldn't figure that out, so some very helpful friends and I tried to push start the car. No luck.

Unhooked the battery and used a portable jumper to jump the car's terminals directly (as opposed to the battery). This allowed the car to start but it promptly died after we disconnected the jumper. Did this a few times with the same result.

At this point, we thought both the alternator and the battery had died. For what it's worth, I noticed a slightly rough idle earlier in the day.

We tow the car 50 miles home. Then, at home, I try it one more time and voila -- it starts right up. Started up again this morning without issue. Talk about frustrating!

What could be going on? Any ideas? Thinking of proactively replacing both the battery (with a traditional lead acid battery) and the alternator now, but I can't figure out why it died and was ressurected. 

Am I right that it was raining when it wouldn't start but then when you got it home and did restart, was it not raining/dry?  

I'm wondering if there is some sort of short that "wet" is causing.  

John Welsh said:

Am I right that it was raining when it wouldn't start but then when you got it home and did restart, was it not raining/dry?  

I'm wondering if there is some sort of short that "wet" is causing.  

Good thought, thank you. The rain actually started about 15 minutes after the car died, though. 

sounds like bad battery symptoms..  The newer the car the more sensitive they are to battery health.  

What i would do is hook it up to a battery in a nother car..  start it and run it.  measure alternator output.  An undercharging alt can kill the battery.

Isn't there a main relay in Miatas that tends to go bad? Could this be a symptom of that?

I would just replace the battery to start. Test the alternator once you have a fresh battery but I would not replace it based on what you have posted so far. 
since it started right up with the other battery (jump pack) it sounds like a battery issue.  

Agree with all her-but I'm reading that you were surprised it died after starting with the jump pack then disconnecting the pack? If nothing is acting as a battery -even a bad one- between the terminals, the engine won't run. I'd not take that as indication of alternator fail. 

Forgive me if I misread what you posted. 

So not dark and raining. I agree with Teh E36 M3, there's no way it runs without any battery whatsoever connected. Probably something came loose and you might want to re tighten everything. I'd run it a few days and hope it's a fluke but be ready to grab another battery.

Teh E36 M3 said:

If nothing is acting as a battery -even a bad one- between the terminals, the engine won't run.

This isn't the case with all cars. I've started and driven a Subaru without a battery.

obsolete said:

Teh E36 M3 said:

If nothing is acting as a battery -even a bad one- between the terminals, the engine won't run.

This isn't the case with all cars. I've started and driven a Subaru without a battery.

Careful - I've killed voltage regulators on a few cars this way.

dculberson said:

Isn't there a main relay in Miatas that tends to go bad? Could this be a symptom of that?

There is, but it's an NA/NB thing. I don't believe the NC has the same problem. 

Thanks for all the help everyone. GRM is awesome and I'm learning a lot.

I'll start with the battery as suggested. I guess I'm just surprised that the battery had been totally fine until it wasn't: no warning signs, just died 15 minutes after ending a session. And then several hours later, without jumping the battery (battery was disconnected when we tried to jump the car since we didn't want to jump a lithium battery) or putting it on a charger, it miraculously started again. Any explanation for that?

In reply to Tyler H (Forum Supporter) :

Yeah, I only ran that car without a battery once, several years ago, in an emergency situation. It was fine afterward but I may have just been lucky.

I wanted to point out that it's not a safe assumption that any car won't run without a battery connected, though. Maybe NC Miatas won't, or maybe they will, and the fact that this one won't is a sign of a problem. I think we need someone else with an NC to chime in.

I don't think NC is a factor here. I think it's a battery thing. I am hesitant to run one chemistry on a maintenance/charging system designed for a different one personally. I need my batteries to be the most dependable part of the powertrain, even if that means an extra 10 lbs. 

To my knowledge, having a lithium battery can explain why it seemed okay until it suddenly wasn't. Lithium batteries keep supplying the nominal voltage until they're highly discharged, then it drops like a rock. The classic signs of a sluggish battery wouldn't really show up until it's too late. Look online for a "lithium ion vs lead acid discharge" plot.

The surprise resurrection of the battery is a bit of a mystery to me. Maybe having it disconnected for a while removed a slight parasitic draw and allowed it to be happy again?

In reply to vsquaredbyrho :

Heat soak dropping the voltage just enough, maybe? Then it cooled off and woke up again.  

Keith Tanner said:

In reply to vsquaredbyrho :

Heat soak dropping the voltage just enough, maybe? Then it cooled off and woke up again.  

Good lithium batteries have both a high and low temp cutoff.  

Does your car have a manual transmission? You could have tried a push starting it instead of a tow, right?

GTwannaB said:

Does your car have a manual transmission? You could have tried a push starting it instead of a tow, right?

According to the post, they did.

In the dark and the rain I couldn't figure that out, so some very helpful friends and I tried to push start the car. No luck.

My guess is also some combination of failing battery and temp cutoff. I don't know if OP is running the stock battery location, or what they can get away with in their auto-x class, but I installed a relocation kit on my NC that uses an NA/NB battery and has an integral cutoff switch. With a NA/NB AGM battery there's a decent weight reduction but it also removes some of the major obstructions behind the radiator, which benefits cooling as well. As a conventional battery I don't have to worry as much about running it down and I can just flip the cutoff switch if I know it's gonna be sitting a while. Might be something to consider.

Wait, don't those batteries have a bms that shuts it down completely if they are hot, or low on voltage?

There is usually a reset with them as well.  

I'd be checking the battery and finding the "owners manual" for it.

GTwannaB said:

Does your car have a manual transmission? You could have tried a push starting it instead of a tow, right?

Not unless you hook a jump pack up, without at least a little voltage, you won't get past the security system..  I had that trouble a few times with my Rx-8. Leaving it sit for a few weeks would result in a flat battery, which meant I couldn't just roll it down my hill without putting the jump pack (which often wasn't beefy enough to actually start it) on it.

Thanks for the feedback, everyone. We did try to push start it with no luck.

Reading through these posts and thinking through the clues, I think the battery overheated and put itself into some safety sleep mode. I know this battery goes into sleep mode if the charge gets too low, but it's possible it also did it from being overheated. I'll call the manufacturer this week to ask.

Also considering going back to a regular lead acid battery. The 20 pound weight savings doesn't seem to be worth the hassle. 

In reply to WonkoTheSane :

And this is why I come here, always new things to learn. I guess I am used to dinosaur vehicles.