A new battery can made that much difference?

Well spring is apon us and I made a deal with myself, to be able to take my car where and when I want this year without worries. So the first thing I did was to get a new battery,because if I played the stereo for more that 5 minutes it would kill it( I got 2 500 watt amps in it).Went out and got a AGM gell and poped it in wensday night and started it up this morning to go get Sunday coffee and smokes.The car never ran this good,maybe just a fluke,I don't think so. After it was up to temp I kicked it ,got the shock of my life , ran like someone changed the motor over the winter. So, I have come to the conclusion that the battery was weak for a long time and I better check and see if the alt is putting out the correct amp's. This could be the problems to alot of bugs in members cars. We keep the car on trickel charges and it keeps the battery up just on the edge. Load test your batteries and if you don't know someone with a tester your local shop will have one . I really can't believe the difference it makes...........Bill    

A new batt can make a difference, in some cases. The engine and stuff are s'posed to run off the battery, anyway. The alternator's job is to keep the battery charged fully. If the alt is down a little on output, it might not be able to keep up with the electrical demands of the engine(ignition), or any electrical components such as the stereo, head/tail/brake lights, wipers, horn, HVAC, etc. A weak alternator will definitely show up as a misfire if the available voltage is not enough to properly charge the batt.
I'd certainly get the charging system checked out. Check the voltage AT the alt, and then again at the batt. It should be the same. Of course, if the output AT the alt is low, it's gonna be low at the batt, to. A good alt will be putting out at least 14.5v while idling, and should stay in that range with head/tail/brake lights on with a small increase in idle speed. Turn the AC/heat fan on high, and see what happens. If voltage drops down below 11v, you need a higher output alternator.

Umm Joel, the output of the alternator shouldn't drop below 12.5 volts, not 11 volts.  Even with everything on in the car otherwise the battery will be discharged.... a fully charged battery should read 12.6 to 12.8 volts, with the surface charge removed(just put a load on the battery after charging it).  Agreed that if the car is running better now with a new battery, that the charging system should be checked out... :) the agm battery should help out a little with the stereo system... those type batteries have a lower internal resistance so when you got her cranked up it doesn't dim the lights as bad..

Dang...I cain't git away wid NUTTIN around hear...yeeesh....
I realize, in theory, the voltage shouldn't go below 12.5, but...in the real world, it happens. Even with a good batt, and a reasonably sound alternator, with the headlights/AC turned on, voltage will sometimes drop below that for a few seconds, until the alt brings it back up. My real point was that if the voltage stayed down, and dint come back up over 12v, a higher amp alt would be needed.

We just gotta keep that Joel guy in check!!!!  I do not want his head to get so big that it will "POP" and get all that "gooshey" shuff all over the web site!!!!!  All kidding aside, Joel is one of our great "Answer Men" !!  He has helped me many times in the past!!!!

Wow you would think Jimmy works for Interstate Batteries or sumptin!

Ahhh  understand now what you meant there, Joel... sorry... yep, it could "drop" below 12.5 ish volts for a moment... sorry...