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Camera battery failing "POST" test

Eventually , by marking and partial swap outs , determined which one of

4 was not up to it especially when environmentally cold, despite 1.5V DVM-battery-test showing ok with that sort of minimal test load. Any chance of deep-cycling, asymetric "ac" charging or whatever, to bring up the performance of A in this list.? B would seem to be ok (for the moment) despite low low-load voltage. For about 1 second duration, with 12 ohm load, then 1.2 ohm load over each battery and the measured voltage, for AA size 2.5Ah NiMH cells A, 1.32V, 1.13V,duff B 1.23V, 1.16V,ok C 1.33V, 1.25V, ok D 1.32V , 1.23V, ok Just how they were, not charged or discharged individually for this test, so B perhaps is more dicharged than the others. So I assume the POST routine is something like 1 amp draw for perhaps only 1mS but fail test if measured voltage is less than 1.15V. Camera a Pentax optio60 pocket camera, requiring 2x AA batteries
Reply to
N_Cook
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Not 1.15V reject level, as only 2 battery contacts for 2 cells, so 2.35V or so ,test fail level

Reply to
N_Cook

I've never had any luck with any camera that used two AA cells. Not much better with those that used four AA cells. Slightest contact resistance or ISR in the batteries will cause it to fail under the very high peak load of the camera. Early NiMH cells had higher ISR than NiCD and performed worse. Not sure that the newer NiMH are much better.

I've wondered if the peak current problem is due to failing caps in the camera power supply not being able to supply the peak.

Toss the cell that doesn't work and be done with it. Be thankful the camera works at all.

Reply to
mike

I have a fancy Maha/Powerex charger (MH-C9000) that has a couple of automatic cycles for this: "refresh and analyze" and "break-in". "Refresh and analyze" is charge, rest for 2 hours, discharge, rest (time unspecified), charge. Both charge and discharge rates are programmable. "Break-in" is a 16-hour 0.1C charge, rest for 1 hour, 0.2C discharge, rest (time unspecified), and a 16-hour 0.1C charge. The manual warns that the "break-in" cycle can take 40-45 hours to complete.

Having said that, I've had a couple of old 1400-1500 mAh or so cells go bad and neither of these modes helped. These were cells that I bought new in 2000 and used a lot since then, so I'm not really surprised that they eventually failed.

If you have any NiMH charger that charges the cells individually, rather than as a string of 2 or more, it might be worthwhile to charge all your cells in that and see what happens.

Matt Roberds

Reply to
mroberds

Just wondered if someone had come up with a clever process to reverse the contamination of the electrodes or the internal chemistry. But looks as though to clearly mark each such high ISR cell, as they in turn fail, for light duty only.

Reply to
N_Cook

That's what I do, for small current needs NiMH may last long time. I still prefer NiCD for higher current, I find them much more reliable and predicta ble than NiMH and they hold healthy a lot longer. All my NiMH cells have ag ed enough to fail to power my digital camera for a reasonable time while my older NiCD still run it through most of their capacity.

Reply to
Jeroni Paul

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