Well put.... and never, ever, under no circumstance, should anyone lick a light socket.
:) ----- Original Message ----- From: "Rob Studdert" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, December 19, 2001 5:22 PM Subject: RE: Rechargeable (2CR5) for PZ-1p > On 19 Dec 2001 at 10:28, Brendan wrote: > > > When I was doing those Nimh tsts I also mesured the > > amperage of the cells, the best alkaline battery testd > > at 1.6V 40~50 ma, a 1600 mah nimh battery was 1.3v > > 130-140 ma, now remember your puttting 4 of these in a > > fg battery pack, so 4 regular or rechargable alkalines > > will provide 160-200 ma to the camera, now 4 nimh or > > nicads are powering 560 ma to the camera, if they > > built it to be powered by a higher voltage lower > > amperage source and you double/triple the apmerage it > > is only a matter of time before you burn something in > > it. No rechargables in my MZ-3, the flashes can use > > them all they want, since I change the AA's in the > > MZ-3 every 3 months but the flahses nightly > > Hi Brendan (and whomever else is interested), > > Sorry it doesn't work this way, the batteries are in series, consider voltage > as the ~potential~ pressure available to push electrons thorough the circuit, > stack the batteries (ie put them in series) and the potential pressure > increases (in fact the voltage adds ie 4 x 1.2 for NiMH, 4 x 1.5 for Alkaline > or 4 x 1.25 for NiCd) > > The current flow in any circuit is determined by the potential of the source > (ie battery voltage), the internal resistance of the battery (determined by > it's short circuit current potential) and the resistance of the circuit which > is the load (ie camera, flash, motor etc). The battery and load resistances are > always in series (resistances in series add ie create a higher resistance) so > the maximum current that can be supplied is governed by Ohms law which is > current (amperes) = voltage (volts) / resistance (ohms). > > Therefore the current can't be forced and usually in any device (excepting a > very badly designed one) the current flow is less when used with rechargeable > cells as the terminal voltage is lower. Generally (given the same sized cell) > the internal resistance of a NiCd cell is lower than a NiMH which is lower than > Alkaline which is lower than the old carbon cells, but the difference should > only be noted under very large load current requirements (ie a low resistance > load approaching what is effectively a short circuit). > > In short if any electronics engineer designs a circuit that factors the > internal resistance of the battery into the design deserves to have a fried > circuit on their hands, so it doesn't happen very often (and it would be very > apparent in the field as not may users ever RTFM). There might be potential in > a badly designed flash gun or motor drive for over-heating due to excessive > current flow but it's not common. > > On the other hand there are now a range of devices on the market (mostly > digital cameras) where they are designed specifically for use with NiMH or NiCd > rechargable AA cell in which conventional AA Alkaline cells will fry the > devices due to their comparatively high terminal voltages (hence they can cause > excessive current flow). > > The battery rating in mAh is simply the absolute charge holding capacity of the > battery like MB of hard disk, it has little to do with current flow in ordinary > circumstances (ie AA use in photo equipment). It can be used to determine the > potential life of the batteries charge for a given current drain, ie if you > have a 1600mAh battery supplying a circuit which draws 100mA then the battery > should theoretically last for 16hours before it is discharged. > > BTW the formula for power dissipated in a load is voltage (volts) x current > (amperes) = power (watts) therefore power = voltage(squared) / resistance so a > small change in terminal voltage has a large impact on power dissipated by the > circuit. > > Sorry about the OT rant but there is no point discussing these sorts of things > when there are fundamental misunderstandings of the laws. > > Cheers, > Rob Studdert > HURSTVILLE AUSTRALIA > Tel +61-2-9554-4110 > UTC(GMT) +10 Hours > [EMAIL PROTECTED] > http://members.ozemail.com.au/~distudio/publications.html > - > This message is from the Pentax-Discuss Mail List. To unsubscribe, > go to http://www.pdml.net and follow the directions. Don't forget to > visit the Pentax Users' Gallery at http://pug.komkon.org . - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
