[PenguinQX]

I'm not too knowledgeable about car batteries, so bear with me here. I noticed that my car has become kinda hesitant starting, and figured it was probably time to change the battery since I'm fairly certain it's the original. I had it tested at an autoparts store, and they told confirmed the battery was "bad". I also noticed that when starting my car with the radar detector on already (Bel RX65), my radar would flash "VOLT" on the display. This only started happening recently, previously the display would just remain on without any change on the display.

I went to AutoZone, and based on some reading I had done on the forum, I went with the Duralast battery for the Mini Cooper to save some $ and weight. Install went just fine, car started up properly etc. Out of curiosity, I tried starting the car with the radar detector on and noticed it no longer flashed "VOLT" across the screen. However, I tested this again yesterday when leaving work, and noticed that the radar flashed "VOLT" this time. I tested it again this morning, and it did the same thing. Is this something to be worried about?

FYI, my radar detector manual states that "VOLT" will appear if vehicle voltage drops below 10.5V.

Any advice would be appreciated, maybe you guys can save me a trip back to AutoZone if this isn't something to be concerned about.

[emax13]

Does the radar go off when the car is off? Sounds like you may have a drain on the battery.

[PenguinQX]

No, it doesn't, but I unplug it.

[RedM3/4]

I wouldn't use my radar detector as a voltmeter. Get a real one and see what the voltage is in the morning for the first start. If it's 12.4 or above the battery is probably ok. But here's some stuff to consider.
- where do you live and what is the temp and range right now? If it is below 20F or so, or not going above 25F or so, you'll start to see a bit longer cranking, which obviously puts more load on the battery, during cold starts.
- you chose a smaller battery, it likely has less cca (cold crank amps) and amp-hour ratings than the original, so the voltage will drop a bit more momentarily for the start, probably this is what your detector is seeing.
Personally, this idea of saving battery weight to me is nearly absurd for folks who spend 85% or more of their time on the street. You have these kinds of issues, and a battery that won't last as long, since it has smaller plates. If you're hard core and have stripped out your seats, air conditioning, carpets and the like, and the car is primarily for the track, ok. otherwise, your skill improvement is going to make a noticeable difference as you progress on the track, but 10 lb or so from a smaller battery will not. If you don't even track the car, cmon, who are you kidding? All you did was raise your headache to benefit factor.
*edit* just noticed you're FI, so you're turning another pulley. I definitely wouldn't go with less amp hour or CCA in this application. If your smaller battery has the same or better ratings, then you should be fine, but that's not normally the case with smaller, lighter batteries.
Just my $.02.
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[PenguinQX]

Thanks for the advice! Point very much taken regarding the benefits of the weight saving -- I figured if I could save like $50 on the smaller battery that would work just the same, the 10lbs would just be a bonus. I didn't buy the battery to save 10 lbs! I don't mind if the battery runs down faster, I believe the warranty has me covered.

I think the unusually cold weather (mid 20s) that has been in my area is part of the reason I was getting the "VOLT" warning. It was a lot warmer here today (high 30s), and message didn't display at all.