[time-nuts] float chargers for oscillator backup power

Bob Stewart bob at evoria.net
Sun Oct 26 23:42:05 EDT 2014

Hi Bob,
The little brick says it's happy with 18-36V.  

      From: Bob Camp <kb8tq at n1k.org>
 To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
 Sent: Sunday, October 26, 2014 10:37 PM
 Subject: Re: [time-nuts] float chargers for oscillator backup power

We seem to have drifted a bit.

This started out as a supply for the Z3xxx Lucent GPSDO’s. In those units, you have a 24 volt switcher that is driven off of the battery or linear supply. Since it’s designed as an isolated supply, I doubt the switcher in the GPSDO is looking for a very clean input. The same is true of it’s need for a tightly regulated input. Yes it’s efficiency will vary a bit with input and so will heat in the box. Still, not a real big deal if the voltage drops a volt or so when you go onto backup. The GPS is still running to keep everything lined up. 

How fast to you need to re-charge the battery bank? For me, not very fast. To keep the batteries healthy, maybe a bit faster than I would like. Lower charge current is another reason to go with a smaller battery if you can get away with it. 



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