During the sub-20deg F weather times (ie 'the bad times'), my battery charge would routinely drop to 1/4...at this time, I would notice that it would be charging quite often.

Now that the weather is 60deg F and higher (ie 'the better times'), my battery goes only as low as 1/2 (lest I am fighting a 15mpg headwind or on a long incline), and is usually pretty close to full by the time I'm done with my drive. Note that this is on 50+ mile interstate trips; cross-town (50mph and below) it doesn't usually drop much past 3/4.

So basically what I'm saying is - your IMA is almost certainly not healthy.