[Nut-upsdev] Tripplite Smart 2200 and Battery Voltage

[Charles Lepple]

On 9/4/07, Brian Ristuccia <brian at ristuccia.com> wrote:
> For my Smart 2200, a charged battery string is anywhere between 25.6 and
> 26.8 volts. I'm seeing nut report 13.0 volts, which seems suspicious. Even
> if the UPS were reporting half of the actual battery voltage to keep
> protocol compatibility with models having a 12V battery system, the value
> of exactly 13.0 seems unlikely.

Do you happen to know the protocol version for your Smart 2200? It is
displayed by some versions of the Windows monitoring software. I
haven't had a chance to backport some of the changes from
tripplite_usb to the serial-only tripplite driver because of a lack of
systems to test with.

> According to the page at http://kursknet.ru/~boa/ups/rtinfo_command.html,
> the :B command returns "relative battery voltage", not any absolute voltage.
> From looking at the source, the calculations seem to be based on an actual
> reading in decivolts or something similar. It also calculates relative
> capacity based on a maximum battery voltage of 13.0 (in nut 2.0.1) and 13.4
> (in nut 2.2.0). The upscmd.cpp in TL_los_cs also uses a similar algorithm.

That could probably be merged with the code here:

http://boxster.ghz.cc/projects/nut/browser/trunk/drivers/tripplite_usb.c#L1245

http://boxster.ghz.cc/projects/nut/browser/trunk/drivers/tripplite_usb.c#L491

... which uses part of the V response to figure out the number of batteries.

> Has anyone looked at this closer already, or should I do a rundown with an
> external voltmeter connected and figure out what the returned values
> actually mean?

Never hurts to double-check with a voltmeter. You may not need to run
it down all the way, either.

-- 
- Charles Lepple