Over on the Antique Radio Forum, Eddystone Eddy asked for recommendations for a dry cell battery tester that tests the battery under load.
My favorite for this is the Simpson Model 379 Battery Tester. I had spotted one at NEARfest a few years back and regretted not picking it up then. I spent some time searching for one on eBay and finally found a nice specimen, although at a steep price.
But it did come with the original box ...
... and test leads.
I had to rebuild them as the old rubber insulation had hardened and cracked.
The Simpson260.com web-site has a scan of the manual.
RCA also made a similar meter, the WV-37.
(Photo credit: Joseph Rebar on RadioAttic.com)
Jeremy Schotter has a scanned copy of the manual for the WV-37A on his RadioRestorer.com web-site. One interesting feature of the WV-37 is that the range switch has blank positions where you can customize the imposed load and the voltage range.
However, you can also make a quite effective battery tester if you are armed with the battery specifications, a resistance substitution box, and a DMM.
Just connect the resistance substitution box in parallel with the DMM, set the resistance value to give the current draw that you want to use when testing the battery, ...
... measure the battery terminal voltage under load, and compare it to the manufacturers data.
Here are some more views of the Simpson 379 Battery Meter.