Originally Posted by andrewwynn

This is very similar to when my battery failed. It could start the car after days off sitting even at 0F, but run an iPhone charger for 30 minutes and needs a jump start. 8 minutes of hazard flash was enough to need a jump start.

Think of it like this: you can take 8 AA batteries in series to get 12v but of course that won't start a car. Your battery was similar, voltage no current capability. The thing is: when voltage is high, no charge will go back in so normal use won't fix it.

There are techniques that will bring a battery back from the dead but mine was old enough and I wanted to upgrade to AGM