Hi Didier:
HP went to super caps for memory backup in their RMB computers. When a new computer arrived it knew the date and time
and if plugged in never lost it.
When stored for a few months the super cap would drain, but no harm done, just
reset the date - time on power up.
Ni-Cad is very forgiving of trickle charge. Ni-MH will accept a very small trickle charge and so the circuit would need
modification.
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Clarke4Congress.html
[email protected] wrote:
I have two HP 8116A function generators of widely different manufacturing date
and different processor board. Both have a NiCad for memory backup.
On the old one, the battery was completely gone and so were many of the traces
on the PWB.
After all was repaired and the battery replaced with a cordless phone pack, a
look at the manual showed a significant change to the charging circuit over the
years.
It turns out the original charging circuit overcharged the heck out of the poor
batteries. I can only imagine they wanted to make sure the battery would charge
quickly, but there was no trickle charge mode, so the high current was there
all the time. The official HP mod to the circuit was more complex than I was
willing to do, so I just removed all the parts and installed a resistor and a
diode from the 5V with about 10mA current and all has been well for at least 3
years now. I seldom run the generator more than 2 or 3 hours at a time (the fan
makes sure you don't leave the generator on when you don't need it :) and the
battery is fine.
It would pay to check the charging circuit in the 5334A to make sure it is not
one of the same bright ideas.
Didier KO4BB
Sent from my BlackBerry Wireless thingy while I do other things...
-----Original Message-----
From: paul swed<[email protected]>
Sender: [email protected]
Date: Thu, 3 May 2012 16:53:55
To: Tom Miller<[email protected]>; Discussion of precise time and frequency
measurement<[email protected]>
Reply-To: Discussion of precise time and frequency measurement
<[email protected]>
Subject: Re: [time-nuts] HP 5334A battery
Tom would agree in general. The charge circuits actually poor. Typically a
resistor.
But here is the other aspect I have run into. The old memories sucked some
real current and would truly drain a LI in 3 months or so. I actually now
measure the draw to understand what I am dealing with. Can I get away with
your trick or am I stuck with a larger battery and in theory plugging the
system in.
nimhs float. Just drop the 1/16 C down...
Regards
Paul.
On Thu, May 3, 2012 at 4:43 PM, Tom Miller<[email protected]> wrote:
I read somewhere that NiMH batteries do not like float charging. You might
do some research on that.
What I do is disable the charge circuit and install a Tadiran Li 3.6 volt
cell. You keep the diode to isolate the Li cell from the normal 5 volts.
These things will last>20 years and they don't leak.
Regards,
Tom
----- Original Message ----- From: "paul swed"<[email protected]>
To: "Discussion of precise time and frequency measurement"<
[email protected]>
Sent: Thursday, May 03, 2012 4:26 PM
Subject: Re: [time-nuts] HP 5334A battery
nimh would be the more modern battery that should work in the nicd charge
circuit.
The HP circuits usually were pretty simple actually.
Regards
Paul
On Thu, May 3, 2012 at 2:11 PM, Scott McGrath<[email protected]> wrote:
Key here is if battery is ni-cd it implies a charging circuit and using
alkaline or lithium batteries may explode If charged
On the hp instruments which I have rehabbed from that era most of them
used nicads with a charger circuit so best advice is replace like with
like
Sent from my iPhone
On May 3, 2012, at 12:40 PM, Brooke Clarke<[email protected]> wrote:
Hi:
Shelf life is the key spec for memory backup batteries. The worst
possible type are rechargeable which go dead in a few months.
Next best are primary batteries where Alkaline (a few years) is good,
but newer chemistries like Lithium primary have>> 10 year shelf life.
So a computer memory backup battery is the best choice. The largest one
that fits the space will have much more capacity than the old battery
because batteries have improved a lot in the past 10 years.
http://www.prc68.com/I/batt.**shtml#CC<http://www.prc68.com/I/batt.shtml#CC>
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.**end2partygovernment.com/**Clarke4Congress.html<http://www.end2partygovernment.com/Clarke4Congress.html>
[email protected] wrote:
The best way is to buy a rechargeable cell pack for cordless phones.
These are typically made with 3 small NiCad so that they don't mind
trickle
charging and are already safely packaged in shrink tubing with two leads
and a connector. When the local Lowe's went out of the phone distribution
market, they sold many of those small battery packs for $1 or $2 and I got
a few that I have been using for that purpose.
Didier KO4BB
------Original Message------
From: [email protected]
Sender: [email protected]
To: Time-Nuts
ReplyTo: [email protected]
ReplyTo: Time-Nuts
Subject: Re: [time-nuts] HP 5334A battery
Sent: May 3, 2012 4:24 AM
[email protected] wrote:
My 5334A Service Manual for SERIAL NUMBER PREFIX: 2426A lists the
following
battery;
Reference Designation - BT1
HP Part Number - 1420-0268
Description - Battery 3.6V .065A-HR NI-CD
Mfr Code - 28480 (which is Hewlett-Packard)
Mfr Part Number - 1420-0268
I haven't opened my unit up to make any checks against this data.>>>
Hope
this helps.
Sure, thank you. I think that the fastest way to replace it would be to
assemble three ordinary 1.2V cells.
Regards,
Antonio I8IOV
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