Tony,
It actually uses five of these batteries. I am guessing they are in series
to produce 5V (okay 6V) needed for the SIMMs at 250mAh. If the point of the
battery is just for use during system swap/maintenance 1-2 hours is plenty
of time. Especially considering that once it is out of the system you can
connect it again to the big battery.
As Tothwolf said it may just be that they are not manufacturing them any
more for use. Or that the 250mAh batteries just don't last long enough for
newer applications. I think what I may end up doing is trying to see how
well the batteries charge up as it stands. If I can get a few minutes out of
them I am good. If not I am considering swapping them out for either 300 mAh
or 400 mAh batteries and just having a longer charge time (but also longer
"backup time").
-Ali
-----Original Message-----
From: cctalk-bounces at
classiccmp.org [mailto:cctalk-bounces at
classiccmp.org]
On Behalf Of Tony Duell
Sent: Tuesday, September 09, 2014 2:25 PM
To: cctalk at
classiccmp.org
Subject: Re: Replacement NiCd Rechargeable Batteries for SemiDisk Card
If it uses SIMMs, which are DRAM, thgen not only msut the SIMMs be powered
to retain the data, but there mus also be some logic -- running
-- to refresh them. That could take considerable current. A 250mA battery is
not going to keep that running for vrey long (I would guess 1-2 hours at
most).
So I think you're right. The batterty is just there topreserve the memory
contents when other suppleis (PC power supply, external battery pack) are
not.
-tony