Car: 2008 Infiniti G35xS

I picked up my G with about 60k miles on it about a month ago and yesterday morning my car took a little bit longer than normal to start but I didn't think much of it. At the end of the work day I went out to my car and it was completely dead and wouldn't start. I found some jumper cables and jumped my car and right away it started and was back.

My first thought was the battery so after letting it charge for a bit I took it right over to the local auto parts store and they tested it. They told me that the battery looked great, had almost 90% charge and everything looked good.

I believed them but was pretty skeptical. I figured maybe I had left a light on or something even though I was almost positive I hadn't.

I drove the car about 20 miles on the freeway home and everything was fine. Then I decided to test it out before I went to sleep so I didn't wake up to a dead car. Sure enough, the car wouldn't start again. We tried to get it to jump off of my friends car a few times and waited about 5 minutes and we couldn't get it to start this time (unlike a few hours earlier). Also, since it had only been about 2 hours since I had the car running, it seems very unlikely that it was anything that was left on.

Other info:
When the car has a little bit of juice it clicks like it is trying to start but it never actually gets anywhere.

My first thought is:
1) The battery seems like the obvious answer. It just won't hold any charge?
2) Possibly the starter?

I am going to try and replace the battery and see if that fixes the issue and if not, move on to the starter.

Thoughts or ideas anyone? Also, the battery looks like it was the one that came with the car. I can't tell a brand but it has some sort of sticker with "84 month limited warranty" on it. Any idea if that is the battery that came with the car or how I would go about getting that replace under warranty if possible? Or should I just pickup a new one and put it in there?

Also, has anyone replaced one of these on an '08 G35? They look like a pain to replace. The battery is pretty far back with some other stuff that looks like it needs to be moved to get it out.

Thx

 

That tells me it's the battery. Can't tell from your description what brand it is, but the OEM one should have Nissan on there somewhere.

Replacing the battery is easier than you think.

http://gshack.org/?p=181

edit: The terminals may also be corroded, slowly dump half a can of coke on the terminals if you have no other way to clean it.

 

baking soda and water also works good, and use a wire brush to clean it up. +1 what soundmike said, most likely battery, it's about at the end of its life and probably has one or more broken cells. You can get it tested at places like sears or autozone for free and it'll tell you its bad right away.

 

That's the weird part. It seems like the battery but I got it tested right after it first died at AutoZone and they told me everything was fine and it had about 90% charge. So I drove home and like two hours later, the car wouldn't start again.

Terminals look clean without any signs of corrosion. The battery is worn and most of the label is worn off but it looks like the OEM or some cheap battery. All I can really make out is "84 month limited warranty" which really doesn't do me any good without any more info. I think I'm going to go pickup a new battery and stick it in there and see if the problem goes away.

Any idea how reliable these battery tests are that they do at AutoZone, Sears, etc?

 

Did they do a load charge? A seemingly "good" battery can fail a load test, which is basically what it goes through in daily use.