It monitors battery voltage both in the short term and longer term so you can see any discharge over a period of time. The ‘strange’ readings from yesterday were because I was washing the car with doors/windows open and closed, and moving the car in and out of the sun.
Yes, it’s a bit of a one trick pony as it does have tests for cranking voltage and charging but the cranking voltage is a waste of time on a hybrid, and the charge test is pretty obvious if you look at it with the ignition on.
Works well for me though as I can get a reading from the front room/bedroom.
For me, the only ‘proper’ way to test a battery is with a high rate discharge tester on a fully charged battery - which I have. I also have a Foxwell battery tester which injects an ac current into the battery to test the impedence. Not as accurate imho, but can give a reasonable guide to the general condition of the battery 👍🏻👍🏻