trog,
The problem is really not with the batteries, I am pretty sure of that - they perform exceedingly well in many other high-drain devices like flashes (Sunpak 383 & Sunpak PZ 5000AF), Minolta A2, r/c toys and even a battery operated baby swing with a heavy motor that depletes normal alkaline AAs in less than 30 mins.
As I understand it, there is a low-voltage cut-off in the camera to tell when the batteries are low in juice. Apparently, the initial batch of K100Ds expect 6V for full charge and cut-off power if it drops below 5.2V. This works well for Lithiums as they power delivery curve maintains a voltage of 1.5V per cell or close to it, through most of the power cycle and dips to 1.3V only when they are really close to running out of juice.
But the NiMH cells have a nominal voltage of 1.2V, and even when fully charged they do not go above 1.44V. So a set of fully charge NiMHs give about 5.7V, but the voltage fall steadily as power is depleted. So as soon as the cells get close to 1.3V, the K100D senses them as depleted while infact they still have more than 50% juice left in them.
Apparently Pentax noticed this problem and later versions of K100Ds have the low-voltage cut-off reduced to meet the characteristics of NiMHs. There are several user reports about K100D giving more than 600 pics on a single set of rechargeable NiMHs. I don't think mine ever crossed 400 - it was mostly around 250.
Anyway all this is speculation and theories, and until Pentax makes an announcement or issues a fix we will not know for sure.
Teja
Originally posted by trog100
i had to throw a dozen of my newest ones away.. i still go for batteres being the problem.. i would certainly try more before blaming the camera.. i also think the largest capacity ones are the least reliable..
i have some three year old 1800 mah ones that work perfectly.. some 2500 mah six month old ones that dont work at all.. not in my k100 at least..
by not work i mean fail after just few shots or refuse to let the camera turn on at all.. age dosnt seem to play a part..
trog