^^^^^^^^^^^^^^^
Get a multimeter. A far more useful bit of kit. I have 2. One stays in the car for emergency use to check power supply to whatever fails. Petrol pump suspect? Step1, is there power to it? Fuse ok? The cheap, basic car one cost about £10 from somewhere.The garage one about £30 I think and does many function checks. Bought from Maplin a few years ago when they were open.
Get a smart charger to maintain the battery.
