I use a ZTS Multi Battery Tester to check all my primary batteries. Needless to say that's to avoid the usual nasties associated with primary batteries. So imagine my surprise today to discover that one of the AAA batteries in the tester had leaked! Luckily no harm done as I caught it in time and a bit of vinegar soon sorted out the minimal leakage. The batteries were well in date and the other 3 were all fine. It just goes to prove that no matter how careful we are to use matched batteries, there's always one. So do I now need a tester to test my tester?