Date   : Tue, 08 Nov 2005 20:12:34 +0000
From   : "A. J. Davis" <mail@...>
Subject: Re: Master battery packs

David Hunt wrote:

>Hi,
>
>My Master has lost its memory today. I opened it up and took the battery
>out.
>
>The battery is a pair of Sanyo Laser Lithium CR12600SE 3V cells wired in
>series, dated 86-03.
>
>These cells haven’t been changed since it was new – they haven’t leaked or
>corroded either. Supposedly, they explode...
>
>Question is what do I replace them with, these old lithium cells aren’t easy
>to get hold of. They are really Manganese Dioxide Lithium. Not a Maplin
>purchase, however, this site lists them
>
><http://www.mdsbattery.co.uk/shop/productprofile.asp?ProductGroupID=733&Bran
>d=&DepartmentName=&DepartmentID=146> £9.40 a pop!
>
>I have seen posts from a long while back about use alkaline cells and a
>diode and resistor. The output voltage from such a configuration is likely
>to be less than 3V once the 0.7V drop across the diode (assuming silicon) is
>taken into account. 
>
>Considering the original battery was 6V, plus my refusal to change batteries
>every year, why can't I replace the battery with a 6V lithium camera
>battery? They've got five times the capacity and more or less the same size
>as what I've removed.
>
>Looking on the web I saw a page referring to rechargeable Lithium cells -
>the cells I removed specifically say "do not recharge" - so I don't think
>that the site is correct. i.e.
><http://lionels.orpheusweb.co.uk/CompNyb/TechStuff/8-Bit/Master128/128BatCon
>fig.html>
>
>Has anyone had experience of the batteries actually exploding or was this
>related to another issue that Acorn kept quiet about?
>
>Kind regards
>
>Dave ;)
>  
>

Lots of places cover this, here's just one example:

http://www.classicacorn.freeuk.com/

I got a three cell holder from Maplin for about 40p. I used to buy a 
four cell holder and modify a dummy battery to hold the diode.