[time-nuts] UPS for my time rack

Ben Hall kd5byb at gmail.com
Sun Oct 11 09:16:54 EDT 2015


Good morning all,

On 10/10/2015 5:07 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
> I was thinking of doing the same a while back, and intended getting a UPS
> and adding a large external battery pack, so if the mains failed late at
> night, I could run the GPS receiver and a few other things overnight, and
> consider starting the generator in the morning.  I contacted a dealer on
> eBay, who specilaises in UPSs. He told me that the smaller units with built
> in batteries will die if you put large external batteries on them.

Years ago, I used to work at a place that would give me all their 
cast-off computer parts, including old UPS'.  I've taken probably opened 
up about 20 of them, from various manufacturers.

The problem is that most don't have good heat-sinking on the power 
transistors.  One unit of a brand I can't remember, all it had for a 
heat sink was an aluminum bar!  Clearly, it was only designed to be run 
for a small length of time.

(It's the same case for the transformers - on several removed 
transformers, I've tried to use them backwards to get 12 VAC from 120 
VAC, and they overheat quickly at more than 50% load.)

If you add external batteries, likely you will overheat and fry the 
electronics as they get far hotter than they ever intended.

thanks much and 73,
ben, kd5byb



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