It appears to me that there's enough room in the HR-V for a normal full size battery, and I've already set it in my mind to do so once the warranty period had passed.
I also own a 2016 Honda Fit EX, and had issues with the battery. The scenario played out differently with that though. I called the dealership to see if it was covered under the warranty and was given false information that it wasn't covered. After posting the issue in here, someone replied back that it should be covered under warranty and they encouraged me to call back and speak with a manager. I called back and spoke with a manager and it should have been covered under warranty. However, as a result of what I had been wrongfully informed, I had already gone out and purchased a full size battery and installed it before calling the dealership back the second time about the issue. To my surprise, however, the dealership did right by reimbursing me for the cost of the battery I purchased to replace the defective Honda battery. The only requirement was that I bring in the Honda battery for them to test it and verify it as bad, to which I did, and the battery did test as bad. So all in all, I'm a happy camper, but Honda batteries suck, lol.