>Date: Fri, 26 Oct 2001 02:30:16 +1000 >From: "Tim Munro" <[EMAIL PROTECTED]> >Subject: EOS Re: NiMh batteries in flash? > >I recently bought 4 x AA NiMh rechargeable batteries that were on special. >I charged them up and chucked them in my 550EX and 420EX flash guns and >noted a 40 - 50% improvement in recycle time - good stuff. I casually >mentioned the batteries in an email to a Canon tech and was surprised to >hear back that they are not recommended for Canon flashes. These are 1200 >mAh 1.2 volt batteries and I think the voltage is the issue. But the main >problem stated was recycle time!, which I know to be improved. I've kept >using them but wondered if someone with a better understanding of >electronics could clarify this further for me.
Generally there are three things that define the use of a type of battery (coindentally, they are the three staples of electronics - voltage, current, impedance/resistance): - Voltage (as you have pointed out). Some digital circuitry runs at 5V, 4x 1.2V from rechargables just isn't enough (4x 1.5V from Alkaline is however). - Current. High drain applications can't handle low current batteries, such as the old zinc-carbon (I think?) batteries. I can't think of a reason why a higher current battery would cause problems. - Source impedance. NiMH, NiCad and Alkalines all have different impedances. This can cause problems in certain circuits that are designed on an assumed source impedance. Sometimes a NiMH can't be used in place of a NiCad because of impedance reasons. This may or may not be the case for the flashes (having said that, I've used NiMH and NiCad batteries in my 380EX no problems). Of course, depending on the age of the manual you're reading, it may neglect to mention NiMH simply because they weren't in widespread use a few years ago! --- Dion Mikkelsen http://dionsplace.terrashare.com/ * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
