[KNS]

The battery in my 2004 BMW 325i E46 is getting up there in years. When the time comes I'd like to replace it with something smaller and lighter. The current battery is a massive thing that weighs about 45 lbs and has about 850 CCA.

On the E46fanatics site some have replaced their batteries with many varieties of smaller and lighter batteries, one mentioned and that I'm considering is a Honda sized battery, the 51R with about 500 CCA. About half the size and weight of mine.

I recall reading somewhere that you should not go down in size/CCA when replacing a battery - true? My car does not require coding or anything like that. It's electronically primitive compared to contemporary cars. It's a bare bones 325i, no big stereo/amp etc. Doesn't require cold starts on sub zero mornings.
I'd also wouldn't mind going down in size with the battery in my 993, also big and heavy.

Thoughts..?