I'm still using ye olde Sony CMD-Z7 on a regular basis and have been
for years. Yeah, I know, it's long since been obsolete and all that
but I happen to like it ! I've no real desire to change it but I'm
now having more than a few problems getting a half-decent replacement
battery for it unfortunately.

The original Sony battery still works just fine in all respects other
than not holding a charge for more than a few hours now. Providing
that the battery doesn't expire completely, all settings and the clock
are maintained even if the phone is turned off and the phone works
perfectly.

Every replacement battery I have ever bought up until recently has
resulted in a minor problem where the clock and some settings are lost
if the phone is switched off. Other than that they work reasonably
well if the phone is always left switched on but generally have a much
reduced life compared to the original. I believe the problem is that
they are usually a slightly lower voltage design than the original
(3.6V rather than 3.9V) and are therefore over-charged plus the
RTC/memory voltage is most definitely significantly lower at around
3.3V max rather than 3.9V

However, the latest replacement I have just bought is blatantly faulty
and/or not compatible at all because the RTC/memory supply is not even
on the right terminals ! Therefore the clock doesn't work at all
because it simply can't be set and any other settings stored in the
RTC memory are not retained under any circumstances either because
it's not even powered. Other buyers have experienced exactly the same
problem so it's not a problem with the phone or a one-off battery
fault and everything still works just fine with the original battery
fitted of course. Needless to say it's gone back.

So ... anyone still got one of these old things in use and can
recommend a supplier of a truly compatible battery that works exactly
as it should ? Thanks for any help (hopefully) coming

--
Mike
email: mikeb <at> twowheels <dot> plus <dot> com