Battery replacement

In my first professionally taught auto tech class we had a Sun Professional Battery tester in the shop. It had two meters on it and two heavy cables to attach to the +- battery posts. It had a variable load cell inside it along with a volt meter and a separate ammeter. Provided it passed a visual test, (posts, leaks, cracks, bulges, etc.) and the electrolyte was above the plates and within about 1.250 to 1.280 specific gravity, we were taught to test 12 volt wet cell batteries with a 250 amp load for about 10 seconds while reading the voltage on the meter with the load connected. Less than about 9.0 volts under load (for most batteries) meant the battery went in the trash. Within a minute, the voltage must return to within .5 volts of the pretest voltage after the load is terminated. The battery was charged first if the electrolyte was below the minimum specific gravity and below about 12.2 volts nominal. It's pretty hard to fake your way through that test and you can easily replicate it with simple previously mentioned tools and by using the starter motor as your load. (remove the fuel pump relay, the coil wire, or engage some other kill system to prevent engine ignition)

This information is a little dated, but . . . .

The instructors were a senior technical representative from Delco-Remy and a German guy with a masters degree in mechanical engineering and 10 years engineering experience in the engine/drive train department at Porsche in Germany. So, . . . if all of the resident experts disagree, you are disagreeing with them! (not me) YMMV!

Chum lee