I recently purchased a (car) battery tester. While it was to test leisure batteries, they are mainly aimed a car batteries and are widely advertised on Ebay/Amazon etc for about £25/30. A typical one is the BU101.
They can test the battery in or out of the vehicle. The out of the vehicle test involves inputting the CCA rating, whether the battery has just been charged, and off it goes. You get a state of health reading and a Replace / Good battery reading and, what seems to be, an actual CCA reading, and the internal resistance on an LCD display.
(In vehicle testing involves using the lights as a load etc but I've not explored this mode.)
Unlike other testers I've seen before, these don't seem to have a load resistor- at least not one that could load the battery seriously (they are too small and would 'cook' if they had).
On a car battery I'm sure is good, it shows good.
On a couple of leisure batteries I thought were on their way out back in Nov but Halfords tested as good, it says Replace. (There were in our old motorhome, I replaced them just in case before I sold it, I didn't want to sell it with a questionable battery).
I'm curious, has anyone else found these beasts to be reliable?
Has anyone any idea how they test the battery, given they don't seem larger enough to have a load resistor inside- at least not one which could stress the battery.