[time-nuts] HP 5334A battery

Fri May 4 00:01:58 UTC 2012

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

shalimr9 at gmail.com 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<paulswedb at gmail.com>
> Sender: time-nuts-bounces at febo.com
> Date: Thu, 3 May 2012 16:53:55
> To: Tom Miller<tmiller at skylinenet.net>; Discussion of precise time and frequency measurement<time-nuts at febo.com>
> Reply-To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> 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<tmiller at skylinenet.net>  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"<paulswedb at gmail.com>
>> To: "Discussion of precise time and frequency measurement"<
>> time-nuts at febo.com>
>> 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<scmcgrath at gmail.com>  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<brooke at pacific.net>  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>
>>>>
>>>>
>>>> shalimr9 at gmail.com 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: iovane at inwind.it
>>>>> Sender: time-nuts-bounces at febo.com
>>>>> To: Time-Nuts
>>>>> ReplyTo: iovane at inwind.it
>>>>> ReplyTo: Time-Nuts
>>>>> Subject: Re: [time-nuts] HP 5334A battery
>>>>> Sent: May 3, 2012 4:24 AM
>>>>>
>>>>>> alanh137 at gmail.com 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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>>>>> Sent from my BlackBerry Wireless thingy while I do other things...
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