On Wed, 10 Sep 2014, Ali wrote:
From: cctalk-bounces at
classiccmp.org
[mailto:cctalk-bounces at
classiccmp.org]
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.
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").
If they are as old as you mentioned in your initial post, I wouldn't keep
them around. Nicds that old tend to leak at random and corrode pc boards.
Try searching for a 2/3AA. I think that is the size you are looking for.
You might also try searching for BYD brand batteries. They are one of the
major manufacturers for nickle based batteries and may very well have what
you are looking for. If the batteries are only being used for short term
backup, a NiMH would probably work ok.