[URThinkingofSome1Else]

Do you use something like the CTEK MXS 5.0 every couple of weeks to keep your battery in good order?
The HRV is reknown for the battery dying when it is not maintained, I use my CTEK MXS 5.0 at least once every 3 weeks.
If you search the forum you will find a lot of complaints about the battery.

I carry one of these in the boot;

This is it being used to jump start a dead Scooby/