Okay, I feel a bit silly admitting this, but I've been driving a hybrid for three years and I only just learned it has two separate batteries. I was reading a guide focused on extending the life of advanced car batteries and discovered that the small 12V auxiliary battery is just as critical as the big traction battery. Apparently, in our heat, that smaller battery can degrade much faster, especially if you mostly do short trips where the petrol engine doesn't run much. The guide explained that switching to an AGM battery is a smart move for our climate and that simple things like parking in the shade can really help. Just thought I'd share in case anyone else was as clueless as I was.
