[mythtv-users] Netbook as low-power combined back-end / front-end?

[rsh1k]

On Tue, Aug 28, 2012 at 1:44 AM, Simon Hobson <linux at thehobsons.co.uk> wrote:
>
> Don't count on the battery being any use. It varies a lot between battery
> types and quality of charge management, but some in particular really don't
> like not being used regularly. So you may find that after a few months of
> being sat there plugged into power, the battery is dead.

Good point.   I would have to monitor it over time to see how it was
doing - battery replacement might just be part of a semi-annual
operating cost.

Periodic battery cycling would be pretty easy - you could do something
like putting the computer on an X10 switch module, and setting a cron
job with HEYU to turn the switch off once per month (or whatever
interval is appropriate), and then back on once the battery level is
sufficiently low.



> On the other hand, if you pick a system that runs off 12V (as some of the
> ION boards do, then in principal you should be able to just hook this up to
> a 12V lead acid battery and use a 13.8V supply/battery charger instead of
> going with a full UPS. Also, for things like the mini ITX boards, there are
> PSUs designed for in-car use that run from a battery and will auto-shutdown
> on low battery etc.

Now there's a whole new aspect!   A car battery would need to be
outside (hydrogen venting, etc), but could provide a substantial
amount of run time.   Plus, it opens up new charging opportunities -
solar, wind, etc - things that with an up-front investment could lower
the annual operating costs even more.     Hmm......


> Lastly, what sort of climate are you in ? Or more importantly, what sort of
> temperatures does your UPS live in ? The VRLA (Vale Regulated Lead Acid)
> batteries they use really don't like heat and despite what's claimed about
> them they will dry out. If the batteries are still running, it may be worth
> prising the cover off to get at the rubber caps on the cells, and putting a
> tiny amount of distilled water in - only a couple of ml, a small syringe is
> good for that - to rehydrate them and see if they improve.
>
> --
> Simon Hobson

I was out in the Northwest USA at that point, so I doubt it was heat
or cold that killed it.   I didn't check the battery acid levels, but
to be honest, I wasn't particularly thrilled with it even when it was
new.   I bought it (a mid-grade APC unit) because our building had a
lot of small power fluctuations... 1/2 second brownouts, that sort of
thing.   About once every week and a half, I would come home from work
to find the computer off.   With the UPS, the computer would receive a
signal via USB when the battery level was low, and do a controlled
shutdown, preventing any issues with filesystem or database
corruption.  It seemed like a good setup.

But in practice, it ended up being rather annoying.  At best, when
new, it had about 15 minutes of runtime and would continue on with
only a brief warning squeal to indicate that the power had been
interrupted.   But once the batteries started to weaken, it would
trip, estimate that it had <5 minutes of runtime left, and signal the
computer to turn off almost immediately.  So even those short power
dips would end up turning the computer off completely.   I started
coming home from work and finding the computer off more often than
before.   Even turning on a hair dryer in the bathroom would turn off
the TV!

I thought about getting new batteries, and I thought about upgrading
to a bigger UPS.  But in the end, I didn't want to spend hundreds of
$$$ and have a massive UPS that was twice the size of my computer, all
sitting on display in the living room.   I got rid of that UPS when I
moved...

- rsh1k