I checked the battery last night and this morning. When I parked the car again around 2pm yesterday it was at 12.52V (having just been driven). Left from work at around 7pm and before I hooked in the battery again it was at 12.39V (note: battery not connected to car from 2-7pm). Drove home arriving 7:28pm, checked battery and was 12.53V (having just been charged by alternator while driving). Unplugged battery again overnight, but checked in again at 10pm last night and it had settled to 12.40V after several hours.
This morning checked battery and it was 12.31V (temperature -7C outside). Started fine, drove kid to school then work, about 40 minutes drive. Got to work and unplugged battery and it was 12.18V! Keep in mind that due to cold mornings, I start heater in car and have radio going and perhaps not driving long enough (and if battery is already "meh") then perhaps all these short trips and cold weather is contributing to the problem on top of an already questionable battery.
My 2011 Honda CR-V has only 80,000km on it (50,000 miles) which is a joke for an almost 13 year old car. Most trips have been short, school and work are 10-15 minutes away. Only when I need to drop kids and then go to work I need to do a longer route. Combined with cold temperatures, running a bunch of things in the morning (heater/radio,etc) and a battery that is showing it's age, plus other factors that may be compounding an already compromised system takes it over the edge after several days like this.
I found this post and going through some of the suggestions and testing, as well as comparing to the voltages I'm getting:
https://www.jdpower.com/cars/shopping-guides/how-to-test-a-car-battery-with-a-multimeterI checked voltage on battery terminals when hooked in and car started, to see what alternator is doing. I'm getting 14.10-14.20V, especially if I rev up the engine a bit and everything is off. Once I start turning on a bunch of stuff (lights, heater, radio) it drops to 13.89V. But according to the article above, anything above 13.5V is still ok, so I don't believe alternator is necessarily to blame. As well, once the battery has a charge, the starter turns over the engine in less than 2 seconds.
I also turned-over the car while trying to read battery voltage while starter was cranking. Keep in mind after all this testing with all accessories on while parking, the terminal voltage on battery had dipped to 11.93-12.00V but I was still able to turn-over the car and for a brief moment I could read the voltage went down to about 9V while starter was drawing power, but I can't be sure (my multimeter doesn't update very fast).
When I left the car this morning at 9:04am it was reading 11.93V. I'll see what happens tonight. I left battery unhooked from the car and will test it again when I leave work. Trip home is only 10-15 minutes (4.5 miles city). Likely not enough to charge my battery much either, but I'll leave it unplugged again overnight and check again each morning.
I'm suspecting it's just a weak old battery that coupled with perhaps some of the usage patterns and contributions from older alternator/starter is starting to dip below reliable cranking power necessary in the cold Canadian mornings, despite having been tested twice at Canadian Tire (using their "fancy" battery testing gear) claiming it's still "ok". Maybe I need to increase my trip time and reduce the use of interior accessories, heater, radio and lights completely to balance out.