Originally Posted by swamp2
After many days of fairly trouble free use my new B3121 is back to the same old shortcomings. To be fair I do often let my car sit for 2 nights in a row without use. After doing this today my trip odometer reset to 0 and the clock once again "forgot" the time. It is my opinion that this battery will be an OK solution only if 2 criteria are met:
1. The car is used everyday.
2. You are in a warm weather climate.
The math still does not add up to me as to why this unit doesn't work better with a longer reserve time but it clearly isn't. I am going to pursue something in the range of 40-60 Ah.
That's the same conclusion I eventually came to after four years of trial and error. Given my infrequent use of the M, I should have conceded this a long before I did. Just being hard-headed I guess. The 'math' you mentioned is what got me too. It was 'supposed to work', but at the end of the day...they all underperformed.
It certainly would have saved me a lot of time, money, and aggravation...
...if I had stopped looking at the specs, and solely concentrated on the real world performance limitations for my application.
I ended up buying a somewhat larger automotive STARTING battery that had a 44Ah rating. It was a godsend, compared to all the headaches I had with the small lightweight batteries I was constantly trying to use.
There are a few batteries that I found, which might be perfect for you. Given your infrequent driving pattern, a slightly larger battery will work out much better than the Braille battery did. You were on
or slightly under
the breaking point for the M3. (for a non-daily driver)
Let me know if you're interested, so I can point you in the right direction as to the best available options in this new (more realistic) Ah range.