2008 Base model - I was starting to have oddball and intermittent check engine and traction control notices.
The kicker was a traction control notice that put the car into reduced power mode and nearly got me hit trying to enter traffic.

The car still started up fine - but in reading the various forum posts; the battery seemed like a very possible culprit.
I have had the car for nearly three years in the desert southwest and batteries don't survive much longer than that out here anyways - so I pulled the battery and headed off to the auto parts store for a test.
Hmm, fully charged but testing as bad - interesting.
$160 later and I'm heading home with a new battery.

Obviously, all the codes cleared themselves while the cables were off and I was cursing the GM designer that decided I should have to play Tetris to get the battery into place.
But eventually, three skinned knuckles, two dropped wrenches and a broken battery terminal replacement later - the new battery was installed.

My car suddenly runs better. I had hoped the electrical gremlins would go away; but I didn't expect better performance.
It idles better, the exhaust opening on WOT is more consistent - I have a small road trip this weekend; I'm curious if my gas mileage improves.

I guess it's possible that these improvements are all in my head - that the CEL and notices going away are making me feel better about everything else - but I actually believe there have been improvements across the board.
Anyone else ever experience all this with a simple battery change?

 

You would be shocked how a faulty battery affects these cars. The computers rely so much on consistent voltage and when the alternator has to fight to maintain proper power with a bad battery weird stuff happens.

 

Just like new batteries in anything that requires them makes them perform better. I'm honestly shocked at the number of posts like "why is my car not starting" or "my car doesn't recognize my fobs"... Batteries are wear items & regular replacement should be part of your routine maintenance schedule. Batteries for a C6 are cheap.

 

another easy way to tell how long you got. If you have you light stay one after you exit the car how long do they stay on?
Mine shut off right away even though the battery test good.
I went AGM due to them able to keep constant power all the time

 

We just had to replace the AGM battery in my wife's 2018 XT5. It would start and run just fine but it has auto start/stop that shuts down the engine at lights. Every time it would restart traction control would light up and chime 4 times and sometimes the check engine light too. The culprit was a weak battery, replaced it and all is good and like you it seemed to run better, real or imagined who knows

 

Side issue, but what Group number battery did you get? My 2008 has a Ford Motorcraft (yuck!) Group 96R battery in it.

 

I got this for my 2009 base

 

Everyone talks about the need for constant voltage in these cars. I don't know much about electronics, and maybe this is a stupid thought but, Could a capacitor be added somehow like kids and their high power stereos for more even power?