Re: Battery Behavior - istDS

[Rob Smith]

From: "Rob Studdert"

I have a D and with NiHMs the behavior is quite stable, the camera works
perfectly until the voltage falls low enough then it simply shuts down.
The only time I've had it become wonky was in extreme cold conditions,
then it behaved very strangely and then shut down, the batteries were
far from exhausted after they warmed up.

Same here, Ni-MH batteries in good condition are quite predictable and 
don't
lead to instability in the *ist D as they approach the discharged 
threshold.



I believe this is because NiMh batteries have low internal resistance. Thus 
they are able to provide high (or at least sufficient)  current to meet the 
cameras operational needs until they have discharged sufficiently to reach 
the voltage threshold at which the camera ceases to function.  This 
characteristic means that camera operation is normally reliable until cutoff 
threshold is reached, in fact you might criticise the D for having rather 
too high a cutoff threshold and hence 'wasting' battery capacity.

In cold conditions internal resistance of (all types of) batteries increases 
and battery performance decreases i.e. current is delivered less readily, 
thus it is entirely possible that although the voltage is high enough to 
register as usable to the camera 'wonky' behaviour may result as the battery 
can no longer deliver. Even though NiMh batteries are comparitively good in 
the cold - try to keep them warm.

Rob.