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Is it bad to put different size/higher amp/migher coldcranking amps?

Does it add more stress on the charging system or on the electrical system?

 
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Nope. It doesn't place any greater stress on the system. However, consider this. A battery which has a higher CCA and is the same dimension as the old battery will have more plates, but thinner plates. That makes it somewhat more prone to failure by vibration and shorting out. However, I'd go with a battery with greater CCA if I had to replace mine. It gives you a longer reserve time for when you run stuff with the car off or if you're like me, leave the dome light on overnight.

 
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The battery is acutally bigger then the orginal size, I've managed to sqeeze it in and secured it somewhat decently.

This was a battery I bought a month back that I put in my fathers old car, so I put my smaller civic battery in his old car. This however doesn't seem to work as well as a lager battery in my civic.

The car doesn't start as good with the smaller battery in it. Hmmm... oh well, that cars never used anyways