One reason I have heard - and I can't recall where, was simply that the "equipment" (in particular - toys) had originally been tested and found to comply with the appropriate requirements, when tested with zinc carbon batteries, and manufacturers are loath to claim that their equipment is ok with rechargeable batteries without doing further tests, so they "default" to making the statement referred to. Seems very plausible !!
Regards, John Crabb, Development Excellence (Product Safety) , NCR Financial Solutions Group Ltd., Kingsway West, Dundee, Scotland. DD2 3XX E-Mail :[email protected] Tel: +44 (0)1382-592289 (direct ). Fax +44 (0)1382-622243. VoicePlus 6-341-2289. > -----Original Message----- > From: [email protected] [SMTP:[email protected]] > Sent: 23 November 2000 23:47 > To: [email protected]; [email protected] > Subject: Re: Rechargeable Batteries > > > Hi Mark. > > You asked: > << why do so many battery operated equipments > state that they must not be operated using rechargeable batteries? >> > > There is no one all-purpose reason, but the two main ones, at least the > ones > I worry about with battery powered stuff, are: > > 1. As you already implied, terminal voltage. > NiCads are typically 20% lower terminal volts than Alkaline cells, and as > lots of battery operated stuff needs a stabilised supply the headroom > required to produce a stabilised supply can take the volts down too low. > > 2. Short circuit current is very high with NiCad's. If there is a fault > internally, or as in one case that I had, if you drop it in water, the > resulting current can destroy the PCB and associated components. Alkaline > > cells, ar even better, Zinc/carbon cells have a much lower short circuit > cirrent and the liklihood of damage, or even fire, is reduced or even > prevented completely. > > The short circuit thing is interesting. My son has a radio controlled car > > with a 7.2V NiCad battery pack. The short circuit current was enough to > melt > the PVC insulation on the battery wires, 1.5mm^2, and I measured it > subsequently at 82Amps. You could probably start a European car with one > of > those! > > Chris Dupres > Surrey UK. > > p.s. Anyone wrapped up a alkaline watch battery in aluminum foil? Don't! ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
