[Nut-upsuser] Re: [Nut-upsdev] Trying to fix "Unsupported combination of battery voltage / nr. of batteries" error

[Carlos Rodrigues]

On 5/1/07, Frank van Wensveen <frankvw at myconnection.co.za> wrote:
> I had seen a line in the megatec driver that apparently supported 36V
> UPSes. However the values didn't make sense to me. Meanwhile I've done
> some digging in the code, the protocol description and what the UPS
> has to say about its own parameters, and now they make even less
> sense. :-) If I understand it correctly, the 36V line in the current
> megatec driver code contains values per cell, not for the entire
> battery. Is that correct?

Not really. The driver doesn't know anything about the number of
cells, or their type, because the UPS says nothing about it. The only
think that can be obtained is the nominal voltage (from the "F"
command) and the present voltage (from the "Q1" command). Since the
vendors can put anything in either of these two values (totals, per
cell, etc)... you see where I'm getting at.

> (234.4 233.9 228.0 006 50.1 40.9 25.0 00001000

The UPS is fully charged here?

> #230.0 008 36.00 50.0
[snip]
> I'll need to fully discharge the UPS to obtain that value. However the
> generally recommended discharge cut-off point for sealed lead-acid
> batteries is 1.8V/cell which on a 26V battery comes to 32.4V. That
> doesn't mean of course that the UPS will wait that long until it
> triggers a load shutdown. So I'll run the test one of these days and
> plug in the appropriate value.

That's ok. Like I said, the voltage at which the UPS triggers a low
battery state (which the driver always reports) should be enough.

> In closing, wouldn't it be more elegant and convenient to have these
> battery values table in a separate config file (or section in an
> existing config file) rather than have it hardcoded in the driver?

The values hardcoded in the driver are the known values. However,
there is a parameter to override this in "ups.conf":

  battvolts = discharged:charged

For example:

  battvolts = 30.0:40.9

-- 
Carlos Rodrigues