just put a optima yellow top 34/78 in my 2006 fx4. Now the battery light is on in the truck.When i run the rpm's up the voltage stays at 12v. Where it used to go up to 14v. Any ideas why? thanks

 

Make sure you have good contact on the battery posts.

That said, are there any more powerful batteries above Optima. I have the 34/78 and it's going dead after less than a year. I'm looking for one I can run with the engine off for a little while.

 

Clean the posts and cables or its a bad battery.

 

A yellow top is a deep cycle battery and unless you are running a big stereo or other heavy users, it may cause your problem. Optima recommends a red top for normal use.

 

A red top time will run your stereo for a good amount of time before it dies unlike the stock batterey.