Perform the battery test and solar cell test when the leads are NOT connected to the beam unit. You can still leave the solar cable in the unit, just remove the wires from the terminals, remembering which colour went where.
Typical battery reading is 4.1- 4.2vdc. Reading if long period of overcast, say 3.9v (wouldn’t want to be much less than this). Low battery warning kicks in at around 3.8vdc (say 3.75-3.80vdc).
Solar panel output on overcast dark day, say 7mA. Clear sky and sunny but low angle winter sun, say 25-40mA.
Bright overhead summer sun 130mA.
This video was filmed on 16.05.20, so in May on a nice day I got 70-80mA.