[time-nuts] Motorola Oncore UT+ firmware upgrade & backup power questions

Pete Stephenson pete at heypete.com
Sun Mar 15 18:18:22 EDT 2015

On 3/15/2015 8:46 PM, Chris Albertson wrote:
> I have one of these UT+ receivers.  Backup is not a big deal.  How long
> will the power be off?  Certainly not for days and weeks.  The backup
> battery only has to last a few seconds or maybe an hours or two.  The real
> problem with batteries is not how much energy they store but shelf life.
> You have to change the 2032 over five to eight years or so just because of
> shelf life.   So some people are using "super capacitors" because these can
> handle the few hours or few days of backup power and have a much longer
> working lifetime r maybe 20 years or more.    F

True, it's not a huge deal. The receiver would be in position-hold mode
anyway, so I would have NTPd configured to send the receiver its known
position and a few other configuration options. Everything else is
easily retrievable from the GPS signal given a few minutes.

Backups of several years are overkill for me, particularly because the
ephemeris and almanac are only good for so long. Backup power in the
minutes-to-hours range would be perfectly fine for me.

My question was prompted mainly because I was seeking clarity as to the
proper use of pin #1: I didn't want to connect a non-rechargeable
battery if pin #1 was only intended for rechargeable batteries, as that
might cause damage. If that were the case I could use a supercapacitor,
but I wanted to be sure the pin (a) could supply power, which the manual
didn't mention, and (b) was current-limiting, otherwise the
supercapacitor would draw enormous currents and possibly cause damage.

Fortunately, it seems that a coin-cell battery will work perfectly. Once
the boards arrive I'll do some tests with the supercapacitor.

Many thanks to all for your help.


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