Rob Studdert wrote:
On 8 Nov 2005 at 12:51, Toralf Lund wrote:
Leon Altoff wrote:
Hi,
The R-CRV-3 batteries are not recommended for use in the Pentax
cameras. They supply too high a current that can cause motors to burn
out.
I'm not sure I understand how that can happen. Aren't batteries voltage
sources, not current sources?
These cells rely upon a higher initial and average voltage to achieve an
acceptable run time (until the camera deems that the voltage is too low to
operate) even though they hold a lower total charge.
Arent they the same voltage as the crv3 lithium batteries that come with
the *istD in the box?
A battery is a complex device, it can loosely be considered as a voltage source
(with unlimited current) in series with a resistance (an internal dynamic
resistance which varies dependent upon load current). Current and hence power
in the a linear circuit increases as voltage rises for a constant load, it's
ohms law.
Being that the terminal voltage is higher than the normal battery voltage there
may be potential for damage of the camera electronics. I assume that the
cameras in question employ electronic power supply regulation, if so these
circuits could potentially be stressed or damaged by an over voltage battery
supply.
Again, I thought Pentax supplied 3v Crv3 batteries (thats whats in my
camera now), or are the batteries in question (R-CRV-3) higher voltage
per cell, i.e. higher than the normal 1.5v? NiMh are 1.2v, but also
have very low internal resistance, so even pretty good loads dont move
the voltage much.
Care to test the theory?
Given the high cost of CRV3 rechargeable batteries, non-uniformity of systems
and specialized chargers required I really don't see why it would be worth the
effort. Also I'm not aware of their self discharge rate either but from
practical experience with other L-ion powered devices they aren't my favourite
batteries in this regard.
Cheers,
Rob Studdert
HURSTVILLE AUSTRALIA
Tel +61-2-9554-4110
UTC(GMT) +10 Hours
[EMAIL PROTECTED]
http://members.ozemail.com.au/~distudio/publications/
Pentax user since 1986, PDMLer since 1998
