Changed my car battery now running low rpm?

My friends battery died in her 03 lancer oz rally. It was the original battery so i went and got her a new one. The battery we got was a smaller then the original one. Now her car idles at 500k rpm and the lights dim at times. Im thinking we just need a bigger battery...Any ideas?Changed my car battery now running low rpm?The battery doesn't affect the idle speed. If the battery is new, and meets the minimum cranking amps for the vehicle, there isn't a problem. Likely the computer that controls the idle lost the programme while the battery was disconnected. Some re-programme really quickly, my car takes a minute or so, some take a few hours of running, like my old car did. The biggest battery in the world won't make it idle faster, you don't even need the battery to make it run.
Changed my car battery now running low rpm?
As long as the amps of the new battery is the same or higher than the old battery or close to it it should be fine. If the amps are much lower you need a more powerful battery. But like the other seller said it won't affect your idle. That has to do with the engine programming which was probably lost because of changing the battery. It should start to run better as the engine and the program adjusts itself.
Changed my car battery now running low rpm?
suggest to give it a few days, idle may straighten out as the computer probably lost its memory when you disconnected the battery. suggest that the battery is more or less for starting the engine,once the vehicle is up and running the alternator takes over and supplies electrical power as required.
YOU JUST ADMITTED TO BUYING A SMALLER BATTERY THAN WHAT CAME WITH THE CAR Y WOULD YOU DO THAT?