Model X 12V issue

[swejw]

Wondering if anyone had the same experience...

2016 Model X 90D about 130,000 km on it roughly 80,000miles.

Had to let my model x sit for about a week without charging and driving due to a parking brake fault and wait until mobile service could come and take care of it, good $1,800 to fix this...anyways..

Just a day after the parking brake service, I had a low voltage battery warning, please schedule service. So I did assuming I had to replace my 12v. But after a few days before taking it in for service on my scheduled date, I replaced my tires to winters and reset my wheel config, now the warning is gone and is not coming back on, its been good 3 days now.

My concern is that if I don't replace the 12v would it die on me suddenly without another warning? or with the code cleared now am I good to keep driving? So hard to tell because there is no way for me to check the condition of my 12v without it actually diein on me.

Please shared your experience if you had a similar issue, much appreciated!

 

[scottf200]

When was the last time you changed the 12v?
I would change that 12v as soon as possible.

 

[ATPMSD]

or with the code cleared now am I good to keep driving?

It probably cleared the alarm with the reset, I expect it will return. Given you are heading into winter why try to eek out a little more time, just replace it.

 

[Tronguy]

Speaking as an electronics troubleshooter who's done shadetree mechanic follies before this:

The 12V lead-acid battery in there has six cells, each roughly 2V. It's a bog-standard automotive battery, except that it's not designed to provide the surge current to turn over an ICE. When they get old, individual cells stop holding charge very well. The "Very Well" part is just what it sounds like: Not going to fall off a cliff Right This Very Second.. but it's not going to get any better, either.

The tricky bit is that you let the car set for a time, presumably with the car's internal DC->DC converter from the high voltage battery to the low voltage battery charging circuit also off; and the (what it sounds like) slowly decaying battery decayed some more.

The car has a voltage sensor on that 12V lead. It's likely to have Lots of Filtering, the better not to have false alarms with. So, let's say the charge has decreased some, and Now You Put On A Load. This makes the 12V droop. At the Same Time, the Car's Trying To Charge The Battery - and it's kind of maybe succeeding, or not. Run around for a bit, and the race tends towards the trickle charger in the car somewhat.. and the fault goes away. Hm.

All right. Back In The Day, if one Walked Into A Bog-Standard Car Repair Shop with a Car That Had a Hard Time Turning Over, the mechanic on duty would haul out this cart with a battery/car tester on it. Attach it to the battery and see what the voltage was. If it's something nasty like 9.5V or something, no matter what's about to happen one way or the other, that battery's a deader. But let's say it's above 12V, meaning that the thing has some charge on it. The guy would flip some switches and press a button, simulating trying to start the car. If, instead of getting 100A or whatever, something pitiful like 20A came out, that would be another indictment of the battery: It's discharge rate is low (or its internal resistance is high), and it's worn out. Time for a new one.

But, after all this, the guy would flip more switches, get the car started, possibly with a replacement battery, and check the charging circuit. Because a bad alternator/generator/regulator won't charge the battery properly, meaning that the new battery the mechanic sold you might get you home, but would then fail again in a few hours to a few weeks, and that would be bad.

Now, with an older battery, it's usually Just A Worn Out Battery, because they do wear out. And 90% of the time the battery replacer will be right. And that other 10% of the time.. well, loose wires, bad DC->DC converter, bad control circuit: Stuff Happens.

Tesla's got the hardware and testing software to do the diagnostic. Depending upon the brand of (modern) car, those OBDII readers can give one diagnostic codes that can help; but there's usually a manual with Steps To Take to make sure that the battery and charging circuit are both working right.

YMMV; I've never had cause to chase down a Tesla battery, although I've done it on a Prius 12V seven or so years ago. And, in that case, I just swapped the battery and that Did It.

Good luck!

 

[swejw]

Thanks guys, just ended up replacing my 12V