Battery Issues

[Hans Brueggemann]

(07-29-2019 06:03 PM)jbodinephotog@gmail.com Wrote:  HP-67

The 67’s battery obviously died and was discarded. I installed the remaining battery without the charger, turned it on, and the display showed it was ready to use as usual (no “red dot” indicating a low battery). But when I put it on its charger with the battery installed and turned it on, the display showed a bright flickering “0.00” and a bright red dot. The battery compartment is pristine, with no corrosion.

depending on the cell technology used in the battery pack, voltages may indeed vary quite a bit. thus, the NICAD cell is characterized (give and take) for
0.9 VDC: fully discharged (for a 3 x AA batt pack: 2.7 VDC)
1.25 VDC: "nominal" (somewhere in the range of 75% charge and leaving it on the shelf for some time)
1.40 VDC: fully charged, measured immediately after removing the cell from the charger.
thus, 4.25 VDC sound reasonable for a fully charged pack and indicates that the charger doesn't have an integrated charging voltage limiter. this is actually true for the HP-67 charger.

as for the flickering with battery pack installed and operating off the charger:
in this operating mode, the HP-67 is actually not using the battery at all, it is taking its power solely from the charger, while the charger is simultaneously charging the battery.
the flickering indicates a faulty component inside the charger.
do not continue to power the HP-67 with it.