Suggestions? Speculations? Experience? 2015 EX

On June 30th, went to start my car after driving 40 miles earlier in the day at 1 pm, it was completely dead and got a jump.

Went to AutoZone the next day to have battery tested, they said it was near perfect.

Two times since then, when I have started my car, I see on my screen - Anti Theft System. The navigation system has lost power. Push and hold the power button for more than two seconds to enable the system.

Yesterday afternoon, stopped for about 5 minutes after driving 10 miles, idling, the car almost died and the radio went off. I made it home the next 30 miles but most of that time the radio displayed Audio Powered Off. I could change the volume on the radio but not the stations. At one point, the outside temp gauge read 108, I have never seen it that hot. Was around around 105 for most of the trip. (I'm in Houston so it is often around 101).

Had someone check the battery a couple of hours later, off it seemed fine. Started the car and the readings fluctuated between the upper 13s and lower 14s.

Thanks for any advice y'all can offer!!

 

Static testing of batteries - like that performed at AutoZone - is not a good indicator of anything other than static performance, because it doesn't reflect real-world driving conditions.

I suspect your battery is gone or mostly on its way out.

If it's the original, time to replace.

If it's a replacement, might want to think about upgrading to the 51R battery size instead of the 151R that's stock.

Where I live, the 51R is a no-brainer - I need all the cold cranking amps I can get in the winter.

Oddly enough, the same is true for warm-weather climates - you need all the cold cranking amps you can get to cope with heat and increased demand on your electrical system.

You can search this subforum for details. The nice thing about the 51R is that's a direct drop-in, no sawing of the old battery tray required.

 

It sounds like it is an issue with the alternator.

 

Seconding alternator. During driving the vehicle runs off the alternator first, and in some instances (German vehicles mostly) uses battery second. Fits are alternator first thoug. Here's what you need to do:

Get a startup->idle voltage reading directly from the alternator, if under 13.6vdc replace, if okay, read voltage during driving (easily done by a scanner or long lead voltmeter). If the alternator looks good during both tests (5-10 minutes of testing between the two should tell you all you need to know), THEN you can assume it's a battery. Good luck.