14 Mar
2016
14 Mar
'16
7:41 a.m.
On Sun, Mar 13, 2016 at 9:41 AM, Rick Bensene <rickb at bensene.com> wrote:
Michael Thompson wrote:
The only difference in NiMH and NiCd charging schemes occurs when rapid
charging them. When rapid charging both types would use a DV/DT technique
coupled with a temperature sensor. The DV/DT is much smaller for NiMH than
NiCd. So if they went to the effort to recharge fast after an event (why
since you could probably do several retracts on a charge) you would not
want to use NiMH replacement batteries. It is unlikely that anything other
than a trickle charge was used with these batteries since it is cheap,
simple and reliable. The trickle current would have been 30 to 50 ma. I
would not use the low self discharge NiMH cells (Panasonic Eneloop or
Energizer Recharge) as they would convert more of the trickle current to
heat and suffer a short life in this application. Non low self discharge
NiMH should work fine.
I think I have a box of unused Sanyo 500-AR cells. If you need some I
could do a quick test and see if any are still good enough to use. The
500-AR are about 1/2 A size. I am sure you can find the dimensions online.
--
Doug Ingraham
PDP-8 SN 1175
The NiCad batteries for emergency head retract are toast. These look like
standard 1.2V 2/3AA 400mAh cells. It looks like some cordless phones use
the
same batteries so I can buy an assembled 4.8V
battery pack.
Any other suggestions for replacement batteries for the RK05?
I've used those 4.8V rechargeable battery packs for cordless phones as the
emergency retract batteries in a few RK05 drives, and they seem to work
just fine. Just make sure you get a NiCd pack rather than NiMH as there
are charging differences and I'm not sure if NiMH batteries would be happy
in the charging circuit of an RK05 (but, who knows, they may work, I just
haven't tried it).
-Rick
The Old Calculator Museum
http://oldcalculatormuseum.com