Can anyone recommend a car battery tester that (a) works and (b) costs less than a tenner? I don't necessarily want a charger, but something to just measure it and keep an eye on it would be useful. I've seen a handful of them which plug into the USB socket inside the car, are these likely to be accurate? Ideally I don't want to have to disconnect the battery to attach the tester. I thought I could use Carista to check the battery but can't seem to find the option - plus the problem using Carista is that the ignition has to be switched on to connect it, and it takes a full minute to scan the system. In the meantime all the LED headlights are on and can't seem to be shut off to conserve power. Any suggestions welcome. Don't want to break the bank as I expect restrictions will be lifted slightly in the coming weeks anyway. Cheers.