Digital Camera Sensitive to a measely 25 mV??

Batteries don't really change much in open-circuit voltage during the useful life, rather the internal resistance increases so you get less voltage out *under load*. You need to measure the voltage under a comparable load to what the camera draws to see how dead they are.

NiMH cells have a fairly high self-discharge rate.

Best regards, Spehro Pefhany

Measring the open circuit voltage of a NiMH cell isn't too useful, to properly gauge capacity left you must measure under load.

Here is a testing procedure for NiMH cells under load that I think I got from someone one in this group. It's been very useful for sorting out camera battery packs:

"--------------------------------------------------------------------------- Get a 0.3 - 0.5 ohm resistor and a pair of alligator clip leads.

Attach one clip to the resistor and the other to the red probe of your VOM. Repeat for the other end of the resistor and black VOM lead.

Put the VOM in voltage mode, 2V scale.

Put the red VOM lead on the plus terminal and the black on the minus. If the voltage reads about 0.8V or better it's pretty sure you have a good but mostly discharged battery. Above 1.1V the battery still has useful charge.

Less than 0.8V: it may be a heavily discharged good battery or it may be one that has lost significant capacity.

If it's zero, remove one clip from a probe and measure the voltage again, if its still zero this is probably a dead battery, but I'd put it on the charger for ten minutes or so and see if it comes off zero, if not then throw it away.

The totally dead ones are easy to find, its the ones that have lost capacity that screw up the pack performance. Fully charge all batteries. Use them as a pack. When the device stops working due to low battery, check the batteries as above. Any battery that has 0.2-0.3 lower voltage than the rest when tested under load has probably lost capacity and should be discarded from the pack.

Like a chain, the pack's performance is limited by the weakest battery.

----------------------------------------------------------------------------

----------"

I've found also that putting the apparently weak cells through one or more conditioning cycles can in many cases bring them back to full capacity.

But I had charged them Feb 14, about a month and a half ago. And all four measured within a few mV of each other, implying that they were all four charged the same. Yes, I realize that the OC voltage isn't a true indicator of capacity, but I've measured other batteries like this with positive results, the lower the voltage, the less charge they have left. And yes, the camera is putting them under load and monitoring them for their capacity, and one might surmise from that that the capacity, according to the camera, is nearly exhausted.

NiMH batteries have horrible self discharge, I've seen batteries have practically no charge after only a few months. Open circuit testing of NiMH batteries is useless. I've seen one fully charged battery from one manufacturer have a voltage almost the same as one almost fully discharged from another. You MUST put them under load to make ANY sort of judgement as to their remaining capacity. There is no other option.

Whether this has "worked" for you before or not is irrelevant.

wrote

check the volts with a load on it.

Wats>