So this has happened to me twice now. After my car sits in garage for 1-2 weeks without driving it I try to crank it or even open the door and nothing happens. Lights don't flash, nothing. The red alarm light steady blinks, so I try to open the trunk with the key and the alarm goes off. I'm thinking it may have been the battery but why would the alarm sound if the battery waa dead. After several tries with the key fob it all of a sudden starts working. Door opens, auto start everything. Has anyone had this problem before.

 

Yeah, commence with charging the battery and see what happens. Go from there.

 

How old is your battery? It sounds like replacement time, but even a new battery can fail prematurely.

 

same thing happened to me. I haven't driven my car since Dec. 5th. a couple weeks ago it had trouble starting so I put on my optima charger it started. I took it off the charger a few days ago and yesterday it would not start at all. my car is rarely driven but it's almost 3 years old. I'm sure it's replacement time. What are you guy's using for replacement ? I read somewhere the AGM batteries won't fit ?

 

Not true. Several AGMs are a perfect fit. DieHard, AutoZone, Advance Auto to name a few.

 

I think even ACDelco has an AGM version that is the right size..Part Number: 48PGHRC or 48AGM
It is only a 36 month free replacement

I just got the Professonal grade Gold series with 42 month free replacement

 

i read something about the fob going into "sleep mode" after extended periods of no use, not sure about that tho

 

You are correct, that is bad info.

 

I always keep the driver window down when parked in my garage, just in case.

 

^^^

Hmm, no need! That is what the removable key is for and the pull cord on the left inner fender well. Just pull and the door opens!

No need to give critters easy access (multi-leg or two leg types!)

In fairness, I do that when I bring the street rod to a car Show! It is always on a charger when parked in the garage but with windows up and the battery in the far right rear interior (like the C7.) It has electric doors and windows both remote controlled. I do have a small mechanical door latch on the door panel. I have a way to deal with the issue if the almost 9 year old Optima Yellow Top dies when in the garage! At a Show, not so easy!

The Show season is starting I best buy a new one, just in case!

 

What's wrong with an OEM battery?

 

An Optima won't fit but many available that do!
This is a PDF of my install last summer in my 2014. I used a Diehard AGM battery for $150 but same one is available with Autozone and Advanced Auto names. Only a few companies, like Johnson Controls, make batteries and brand label for others including Delco! AGM's have more capacity.

http://netwelding.com/Battery_Issues.pdf

There are some tricks in replacing the battery. Not as simple as in a C6!

 

Uhm it won't start my car. And I don't want to replace a battery every 2 years. I have an AGM battery on my classic that I drive even less than my vette but the fact that it can stay charging all the time is a plus.

 

^^^

Funny, I have an Optima AGM in my Street Rod that is now over 8 years old. Like you it is always on a small charger.
My 2014 was my DD and I replaced that battery after 3 years with an AGM battery and will do the same with my Grand Sport in ~3 years if it lasts that long! I don't put it on a charger, it's my DD and typically drive 4 or 5 days week!

 

Funny things seem to happen in Corvettes when the battery gets low, give her a change.

 

What is the expected life of the OEM battery? I am coming up on 3 years, 30K miles... might give her a proactive change for once

 

Those that use a charger find the battery lasts longer, as I do on my street rod. It you don't and put on enough miles to keep it charged should last 4 years perhaps 5.

If however you make short runs the battery will not fully charge and expect a 3/4 year change when I want to do it is far better then needing to change in the winter when it's not on sale and it has to be done. If that is your case and all is fine now might wait until late summer when there is a sale on an AGM battery! Bit of a PIA in the C7 because of the location.

 

Going back to my '97, I've found that these cars use enough power to drain a battery in two to three weeks while sitting. That's not good for the battery and if it freezes, it's damaged. Battery life also impacted.
I use a tender whenever I know the car will sit for a week or more. Keep it topped off! You can't let it die!
As far as an AGM battery, I wouldn't buy one unless the car had one from the factory. It may not matter going to AGM but I've read online (must be true) and spoken to mechanics about putting a standard battery in an original AGM car is a bad move. I guess it can damage the electrical system.

 

^^^
First the C7 is different than past Vettes. The computer shuts everything electrical off (essentially) in <10 minutes. Leave a light on and the car shuts it off. The Service Manual says an 80% charged battery will start the car after 30 days. Many forum post state that works. Left my 2014 that was never on a charger several times for 2 1/2 weeks while on vacation. Started fine.

Don’t want to sound like your mechanic doesn’t know what he is saying, but he doesn’t nor does the info you found on the net!

Put an Optima AGM battery in my C6, have one in my Street Rod and put a Diehard AGM in my 2014! Higher capacity and the charging system is happy to charge it like any other battery!

 

My keyfob battery was the culprit when I had this issue, but I can tell my bat is on the way out in the car. Been 4 years and still the stock one. I will prob replace since climbing in the hatch to pull the safety release on the door to get in when the battery dies is not all that fun.