Time for a new battery.

Car was having a slow start two days in a row. At first I figured it was just because the weather has cooled down so much the last couple days (especially overnight). But the fourth time I tried to start my car, I got just clicking (all electronics work, dash lights, etc, voltage shows about 8-9 on the gauge).

I jumped it and it runs fine, but after driving it for about 40 mins, it will not start again.

I would like to put in one of those Braille batteries (it looks like the B3121 meets the specs), but I'm not sure what all I need to consider. The 3121 has 550 cca and 75 mins reserve capacity. Is there anything else I need to look at or consider for a daily driver? The car lives in Phoenix.

Things to consider:

Temperature(too hot/cold can kill a battery)
How long the car sits without being started
How long you run accessories without the engine running
What other accessories you have added(stereo, aftermarket anti-theft system)

Braille is a lightweight racing battery if memory serves me correctly, and I haven't heard any negatives. Give it a shot.

Throw an AC Delco in the car and be done with it. You'll spend a bunch more on a Braille and need to buy or fab a mount. Batteries these days easily last 7 years or more.