The starting motor itself makes a pretty good field expedient "battery tester". Turn on the headlights. Attach a voltmeter to the battery posts (not the cable terminals) and have someone step on the starter pedal. If the starter doesn't turn, but the voltage stays around 12V. and the headlights don't dim noticeably, you have a dirty connecdtion somewhere in the starter circuit- - - -either hot of ground. If the battery voltage bottoms out close to zero and the headlights go out or get very dim, the battery has an internal problem. After 15 seconds of cranking at normal speed (ignition switch off) the battery post voltage with the starter still turning should be above 9.5 volts. Don't use the starter motor as a tester repeatedly- - - - -let it cool down for 30 minutes or so after a couple of "tests".
Jerry
