Those were used to check each cell on older batteries that had tar over the tops. Notice that the gauge range only goes up to 2 V, which is the nominal voltage of a single lead-acid cell. The points would jab thru the tar and contact the lead connectors underneath. Not usable on newer batteries with plastic tops unless you destroy the plastic covering. The tar would heal back over the lead where the holes were made.


Kevin
1951 Chevy 3100 work truck
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Photos
1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.