15 Mar
2016
15 Mar
'16
4:08 p.m.
Interestingly(?) both my RK05 and RK05J had an assembly of 3, not 4, 2/3rd
AA NiCd cells for retract, completely decayed of course. I replaced them
with 3 discrete tagged NiMh AA cells (plenty of headroom) soldered and
shrinkwrapped. They work fine, lots of retract force. The clip which holds
them is shaped for only 3 cells so it seems as though there were at least 2
variants. I read the circuit diagram and could see that it would make little
difference whether it was NiCd or NiMh (or for that matter 3 or 4 cells). I
think DEC were a bit overgenerous with the trickle current (though IIRC
NiCds were rather leakier back then).
From: tony duell <ard at p850ug1.demon.co.uk>
The DEC RK07 (and I assume RK06) used 8 1/2 AA cells in a pack (like
2 RK05 retract batteries in series). When I replaced those, I used 2 of
the cordless telephone batteries (that have been recommended for
the RK05) in series.
-tony
15 Mar
15 Mar
4:25 p.m.
On Mar 15, 2016, at 4:08 PM, Robert Adamson <bob at
theadamsons.co.uk> wrote:
Interestingly(?) both my RK05 and RK05J had an assembly of 3, not 4, 2/3rd
AA NiCd cells for retract, completely decayed of course. I replaced them
with 3 discrete tagged NiMh AA cells (plenty of headroom)
From the various comments, it sounds like NiMH is a
useable substitute. On the other hand, NiCd batteries are still readily available.
paul
16 Mar
16 Mar
4:12 a.m.
On Tue, 15 Mar 2016, Paul Koning wrote:
From the various comments, it sounds like NiMH is a
useable substitute.
On the other hand, NiCd batteries are still readily available.
Yes, but NiCd cells really don't like being charged only and never
discharged. And they tend to crystallise quite badly with age and
"misuse"; best examples are 3.6V NiCd battery packs as CMOS battery on
many mainboards.
Christian
1:24 p.m.
On 16.03.2016 09:12, Christian Corti wrote:
On Tue, 15 Mar 2016, Paul Koning wrote:
Additionally the NiCd never keep charge, if , like me, the drives are only fired up
once a year...
I am thinking of just adding some wiring to an external battery.
Jos
From the various comments, it sounds like NiMH is
a useable substitute. On the other hand, NiCd batteries are still readily available.
Yes, but NiCd cells really don't like being charged only and never discharged. And
they tend to crystallise quite badly with age and "misuse"; best examples are
3.6V NiCd battery packs as CMOS battery on many mainboards.
Christian
1:32 p.m.
On Mar 16, 2016, at 1:24 PM, Jos Dreesen
<jos.dreesen at bluewin.ch> wrote:
...
Additionally the NiCd never keep charge, if , like me, the drives are only fired up once
a year...
I am thinking of just adding some wiring to an external battery.
I wonder if it might make sense to replace it by a capacitor. For this kind of
application, the total capacity is not an issue at all, but only the available current for
a fraction of a second. By that measure, it doesn't take all that large a capacitor
to do as well as a battery; the difference is that the battery can sustain that current
far longer -- which doesn't matter here.
paul
2:38 p.m.
I'd think a stack of supper capacitors would do it.
Dwight
________________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Paul Koning
<paulkoning at comcast.net>
Sent: Wednesday, March 16, 2016 10:32 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: DEC RK05 Emergency Retract Batteries
On Mar 16, 2016, at 1:24 PM, Jos Dreesen
<jos.dreesen at bluewin.ch> wrote:
...
Additionally the NiCd never keep charge, if , like me, the drives are only fired up once
a year...
I am thinking of just adding some wiring to an external battery.
I wonder if it might make sense to replace it by a capacitor. For this kind of
application, the total capacity is not an issue at all, but only the available current for
a fraction of a second. By that measure, it doesn't take all that large a capacitor
to do as well as a battery; the difference is that the battery can sustain that current
far longer -- which doesn't matter here.
paul
3084
days inactive
3085
days old
5 comments
5 participants
participants (5)
-
bob＠theadamsons.co.uk -
cc＠informatik.uni-stuttgart.de -
dkelvey＠hotmail.com -
jos.dreesen＠bluewin.ch -
paulkoning＠comcast.net