3 1/2-year-old 75-month battery--starting problems in winter but starts fine in summer, 1 1/2 years wouldn't start, month later wouldn't start--mechanic hadn't put caps on tight, water all leaked out, refilled, charged by a handyman, OK last year, OK at oil change 2 months ago, wouldn't start a month ago, jumped by tow truck, added solar panel maintainer hooked to battery, OK last week, won't start this week. Never opened up the caps before (not a maintenance-free battery) but noted that frozen water, ice above the hole mark. I drive it only one or two days a week, mostly medium-length trips. It's outside so I can't have a battery tender.