[time-nuts] HP 5065A battery pack

Dan Rae danrae at verizon.net
Sat Nov 21 16:49:52 EST 2015

On 11/21/2015 6:13 AM, Bob Camp wrote:
> Hi
> The key issue is that there has been a lot learned about charging batteries
> since the 5065A was designed. Just as other parts of the 5065 can be improved
> with some work, so can the battery charger. Given that NiCad’s aren’t cheap,
> it’s worth noting that the circuit could be worked on *before* somebody buys
> a bunch of batteries to re-cell one.
> Moving a bit further off topic and back to our original conversation when you re-did
> yours (2 years ago?) - you don’t get a lot of standby time even with the full load of
> NiCads in there.
Bob, I stopped writing dates on the chart thing inside the pull down 
cover in August 2004 since the numbers had not changed significantly 
since 2002 (and still haven't) which in fact must have been when I did 
the battery.  Time flies... A bit more than my guess of 5 years!   It 
got a check recently when we had an outage that lasted for a good twenty 
minutes and the green light stayed lit.  -hp- spec is for more than ten 

And incidentally the schematic shows the battery as 25.2 Volts which 
might indicate 21 cells, although I'm sure it would work with 20 and 
maybe there have been early versions that did have 20; mine is late, the 
last but one serial prefix.

It's certainly possible that the circuit might be improved but it does 
seem to perform as advertised as is.  For extended periods than there is 
always the DC input as has been pointed out.  I suspect this option was 
more for moving the thing from one lab to another adjacent rather that 
flying clock trips or mountain climbing :^)


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