K3S and power failure

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K3S and power failure

Bob Novas
My house occasionally has a power failure, typically lasting less than a
minute. One just happened.  Do I have to worry about operating the K3S and
having a power failure?  It would be like turning off the power supply
without first turning off the K3S, and I understand that's not recommended.
Do I need a UPS for the K3S?  What would be nice would be a small battery
that powered the smarts independently of the mains supply.  Bob - W3DK

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Re: K3S and power failure

Bob McGraw - K4TAX
Well that condition of a power failure is never advised.   Likely the
radio just won't save the last parameters.   And yes it is never advised
to turn off the power supply before turning off the radio.    The radio
saves the last used parameters when the power switch is depressed.  
This won't occur when the supply is switched off before the radio.

Yes, a UPS would be nice and will prevent such events but......be sure
to get one that is sine wave {they usually generate less crud}  and one
that does not generate RFI and birdies.    Usually "cheap ones" won't
pass muster in this regard.  Good ones run with the output locked in
phase with the power line and may actually supply power 100% of the
time.   Others switch quickly to prevent power interruptions to the load.

The "quiet" method is to float a small battery, depending on how long
you want to hold the system up, determines the Ah rating. If your supply
is running a solid 13.8 to 13.9 then a lead acid battery of the
garden/lawn mower type works just fine.  Connect the battery across the
supply output.  A 20 amp or so fuse should be in the positive line
between the battery and supply.    You should check to see when the
supply is off that it does not draw current from the battery.  Most
don't, yet some do.  This will discharge the battery when the supply is
off.     I don't advise using diodes to isolate the battery from the
supply and then feed the radio due to the voltage drop across the
diodes.  Plus the diodes will need to be rated at the current of the
supply and/or radio current demand, and those will likely require a heat
sink.

73

Bob, K4TAX



On 7/17/2018 8:46 PM, Bob Novas wrote:

> My house occasionally has a power failure, typically lasting less than a
> minute. One just happened.  Do I have to worry about operating the K3S and
> having a power failure?  It would be like turning off the power supply
> without first turning off the K3S, and I understand that's not recommended.
> Do I need a UPS for the K3S?  What would be nice would be a small battery
> that powered the smarts independently of the mains supply.  Bob - W3DK
>
> ______________________________________________________________
> Elecraft mailing list
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> Message delivered to [hidden email]
>


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Re: K3S and power failure

Phil Kane-2
In reply to this post by Bob Novas
On 7/17/2018 6:46 PM, Bob Novas wrote:

> What would be nice would be a small battery
> that powered the smarts independently of the mains supply.  Bob - W3DK

What I have is a 12V DC battery bank (150 AH) feeding all my radio
equipment - transceivers, scanners, processors), a 1500 VA UPS for the
desktop computer and printer, and a 500 VA UPS for the phones and
digital distribution system.  The charger for the battery system (which
can handle full load if the batteries fail) and the laptop supply are
fed off the mains.  That system can and has powered the radio room for
several hours with less than 1 volt drop in the nominal 12-volt system.

73 de K2ASP - Phil Kane
Elecraft K2/100   s/n 5402

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
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Re: K3S and power failure

Bill K9YEQ
Ditto,  I have had my system in place for at least 10 years. I bought a deep cycle marine cell which can recover with extreme discharge cycles.  I have had it last as backup from a mains power outage for 30 hours, using the K3s briefly for a couple of hours at 50 watts.  Would never had known power was out.  The PC backup didn't last as long, didn't matter as the ISP failed within hours anyway.  

73,
Bill
K9YEQ

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Phil Kane
Sent: Wednesday, July 18, 2018 2:07 PM
To: [hidden email]
Subject: Re: [Elecraft] K3S and power failure

On 7/17/2018 6:46 PM, Bob Novas wrote:

> What would be nice would be a small battery that powered the smarts
> independently of the mains supply.  Bob - W3DK

What I have is a 12V DC battery bank (150 AH) feeding all my radio equipment - transceivers, scanners, processors), a 1500 VA UPS for the desktop computer and printer, and a 500 VA UPS for the phones and digital distribution system.  The charger for the battery system (which can handle full load if the batteries fail) and the laptop supply are fed off the mains.  That system can and has powered the radio room for several hours with less than 1 volt drop in the nominal 12-volt system.

73 de K2ASP - Phil Kane
Elecraft K2/100   s/n 5402

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
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