# [Nut-upsdev] Mustek PowerMust 848

Marian Ciobanu ciobi at inbox.com
Wed Jan 21 11:51:44 UTC 2009

```> Although the 'blazer' driver is able to talk to your UPS, I have no
> information on it. You may be right that the UPS is able to report
[...]

OK, I started Windows and unplugged the UPS (I know I'm not supposed to
do that), then I wrote down the reported voltage and battery charge, and
then I put the results in a spreadsheet and created a chart. The linear
relation between charge and voltage is obvious, so I'm quite confident
that the charge as reported by the Windows app is voltage-based. There's
still a slim chance that the UPS might be able to report the actual
charge, as the software is generic (WinPower) and might not be aware of
all the capabilities of a particular UPS, but I'm not going to pursue
this any further; it looks pointless.

I believe the voltage-based charge calculation can be improved, though;
the main idea is to use different limits for high and low voltage,
depending on whether there is AC power or not. When I pulled the plug,
the voltage dropped from 13.7V to 11.8V and the charge from 97.3% to
47.3%. I let it run on battery until it hit 11.3V and 34.2% and the UPS
started to beep more frequently. After I plugged it back in, the voltage
went up to 12.4V and the charge to 63%. While what happened with the
voltage makes sense, the same can't be said about charge. So I'm going
to run some experiments and then I'll probably make some code changes
to have different limits (or perhaps different formulas) used for charge
in these 2 cases. (The main thing that I'd like to check is whether the
voltage decreases linearly with time for a constant load.)

Now concerning battery.voltage.high/low: this didn't work for me.
I wonder if I made a mistake in the config file. Here's my ups.conf:

[mustek]
driver = blazer_usb
battery.voltage.high = 13.8
battery.voltage.low = 10
port = auto
desc = mustek

With these settings, upsdrvctl doesn't even start. I eventually got it
working, but only after making changes to blazer_makevartable() and
blazer_battery().

Did I misunderstand something in the manual?

--------------------

[...]
>> It looks like KNutClient forgot to disconnect. Or maybe I messed up
>> something.
>
> Try the latest version from the trunk. It indeed looks like KNutClient
> forgot to disconnect, so this version will now force disconnect the
> client if it appears to have data available, but doesn't respond when
> we ask for it. This should probably solve this problem.

I tried. It fixes the issue.

Thanks,
Ciobi

```