[Nut-upsuser] UPS Losing Connection

Stuart D. Gathman stuart at gathman.org
Wed Sep 23 21:09:49 BST 2020

I solved this problem a few years back.


The short answer is USB is broken on the model (but the power management
is excellent, handling switchover to generator power without a hitch).

The workaround is to do a usb port power off when the Tripplite USB
hangs.  But hubs that actually implement this mandatory feature (must at
least support powering all ports off) are getting hard to find.  The USB
chips implement it just fine. The hubs don't bother connecting the pins
and just wire to +5V.

The good news is that with CentOS-8, the kernel automatically does 
the port power off, so you don't need my kludgey software fix when you go to
8.  You still need an actual standard conforming USB hub however.
If the port on your server isn't, you can buy an external hub
like I did.

On Tue, 22 Sep 2020, Kirk Bocek wrote:

> Installed a new Tripplite Smart1500LCD on a CentOS 7 host using the usb 
> connector. Nut does connect:
> $upsc ups
> battery.charge: 100
> battery.runtime: 1407
> battery.type: PbAC
> ...
> But after a half hour or so the connection is lost. Restarting nut 
> re-establishes the connection.
> Any idea what might be causing the dissconnection?

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