Thursday, June 30, 2011

good day sunshine

I have been researching small solar setups, of the type that feed a
couple 12v deep cycle batteries. I am interested in using a small panel
to charge and maintain a deep cycle battery in my camper shell.

The most interesting piece has been the charge controllers, the piece
that takes the varied level of power from the solar photovoltaic panels
(PV hereafter) and keep the batts optimally charged.

Both the inputs and outputs can be complex. Output is generally
three-stage charging: bulk (80% charge, acceptance (remaining 20%), and
float cycles (maintenance). That's interesting enough.

The input is somewhere between interesting and fascinating. The main
things to understand are:
1. depending on charge phase, the controller needs to put out 14.8vdc
at the most.
2. PV panels don't output 12v; the basic ones put out something like
18V max and many are much higher. This allows enough headroom for poor
solar condtions to still yield nominal 12vdc.
3. wattage ratings are given at highest power output, say 17.5vd x
2.58a = ~50 watts.

So, if the max you can use is 14.8v at the controller that would be
38.13 watts. Leaving a good bit (over 20%) on the table. Normal
controllers do this, effectively necking output from the PV to the
required voltage.

Another, more complex (and $$$) MPPT-type controller sweeps the panel's
output looking for maximum power. It does a DC-DC conversion dow to the
desired 14.8vdc (in our example); during this conversion the excess
voltage is yield as extra amperage. The output is very close to the
PV's rated output, minus about 5% losses incurred in the DC-DC conversion.

Under average conditions the MPPT controller yields about 10% more
power. In certain conditions it can yield 30% more. In rare conditions
when the PV is underperforming and PV output voltage is closer than 5%
to the very close to the required voltage* it can actually be less

The question in my mind is this: is the better controller worth 3x the
price. The difference is about $100. Can I imagine a situation where
having 30% more power would be worth $100. Yeah. So I'm leanintg that
way. And the better controller would be usable with better gear later on.

I may grab a PV and see what kind of real-world vdc I'm getting from it.
If I rarely dip below 15.58vdc I may save up for the better controller.
Really cheap, basic controllers (not the one's we are discussing) are
available for $15, and could be used later for backup.

phase one: get deep cycle battery. build small junction box for
accessories (fan, laptop charger, phone chargers, LED lights). Set up
AC charging regime. Test accessories.

phase two: get PV panel, mount on camper shell. Measure real-world
output in volts. Make decision on controller.

phase three: install conrtoller

A final thought for those unmoved by solar: there are home setups where
you can take as much power from the PV as needed for your battery bank
and put the rest into your wall socke. This is called "grid tie".
The extra voltage is the remainder is inverted to 110v and plugs into
your wall socket like any other plug. The inverter reads wall
voltage/hertz and outputs what the wall wants. Since the inverter
matches what the wall is putting out if the wall power is lost the
inversion stops.

Might be 20w, might be 200w but the power is being put to use instead of
wasted. Think about the positive input on the grid if everyone did that...

* needing 14.8v, getting 15.54

posted by email

Friday, June 17, 2011

battery assault

A coupla years ago I scored a 24v B&D electric mower off freecycle. I
normally use a reel mower but the electric is useful at times:

* can collect clippings to alter the green:brown ratio in my compost piles.
* can mow down tall stragglers in the yard the reel mower pushes over.

The electric has never been 100%; the donor said he put fresh batts in
it but I suspected them and the braindead charger that comes with. He
suspected the motor's brushes so I pulled them and touched them up with
a file.

I finally bought some replacement 18A 12v for the mower; they are wired
in serial when installed. Before installing them I charged each
seperately with a Battery Tender Plus 12v unit so they would be closely
mated, voltage-wise. Then I connected them and installed them in the
mower. I put them on the all-singing, all-dancing 24v BatterMINDer
charger (queue angelic voices) until I could test drive it.

Mowed some deep grass in the alleyway since everything was short.
Worked great. Composted the clippings and back on the 24v charger it
went. I feel good about this.

written offline and synced later

Tuesday, June 14, 2011

Sign of the economic times

I'm still getting rejection letters from job I applied to in January or even earlier. Most say "sorry, we picked somebody else" but some say "sorry, our funding went away" or similar.

I think this means companies are either being very picky (because of the long delay, not because they didn't pick me :-) or are dealing with intermittent hiring freezes.

Monday, June 13, 2011

Super 8

Went to see Super 8 at the Galaxy drive in.

Good movie that reminds us a blockbuster doesn't have to be stupid.

And, oh yea: Best. Train crash. Ever.

JJ Abrams is a master. Crowd actually clapped and cheered at the end.

PS: watch the credits.

Saturday, June 11, 2011

Snyder's sea salt and cracked pepper pretzel pieces

Found a bag at Big Lots, which likely means it was a market test that

1. 'pieces' = broken parts we wanted to use somehow
2. tastes just like croutons
3. fantastic

written offline and synced later

Friday, June 10, 2011

chicken attack

Well, attack ON chickens.

Last night the wife heard wild bocking noises and went out to find a cat
trying to get at the chickens through the chicken wire. No blood, but
the cat got a small clump of feathers pulled through the wire.

Suspect is a black cat with white feet. No collar. Looks like I'm
going to have to rent another live trap from the Richardson pound...

emailed in

Sunday, June 5, 2011

Night Shift

Some thoughts about the new job. If they make even less sense than
usual it's because they're all written around 2am for reasons that will
be shown below.

This job is strange. I think it is most similar to working in a network
operations center (NOC) only with things and people rather than data.
It's 95% visual, with maybe a couple of phonecalls per shift. It's also
95% transparent to the public. Nearly everything done on the job
(keyboard, mouse, etc) is published in near-real time. A minute or two
delay while servers sync up, maybe. If I write a sticky note and put it
on a co-worker's monitor that's about the only thing that's not directly
or indirectly visible, and there are times when you might see that, too.
Told you it was strange.

-= timeshift =-
First things first. This is a night job. I go to work in the evening
and come home the next morning and go to sleep. I've been doing it for
a few weeks now and my body is almost used to it.

Working nights is not hard, though it /is/ weird. Transitioning to
nights was brutal, however. The first week felt like impending death,
like a continual hangover without the headache.

commute is generally better
outdoor temps are generally lower; I can walk outside on my lunch
it is very quiet. For 80% of my workweek I am the only worker
time off is very productive (see below)

The timeshift takes some adaptation. I brew a pot of coffee and bring
it with me in a big, industrial 1960s Uno-Vac steel thermos. I think
you could beat a shark to death with it if you had to.

Days off for nightshift people can go one of two ways:
1. try to keep a normal-to-others schedule. This allows for fragments
of Normal Life at the cost of continual walking death fatigue.
Basically it's changing body clocks 2x/week. Uh, no.

2. keep your working schedule. This means stay up all night on your
days off and sleep during the day as "normal". This is the approach I
have taken. Being up all night when the world sleeps feels like
time-expansion. The night lasts forever. I can get more done in one
night than in a week of normal free time.

-= 4x10 =-

This is my first experience working 10hrs x 4 days. The main benefit
would appear to be three days off in a row, but IMO the benefit is in
the 20% reduction in commuting (time, direct expenses like gas, and
indirect expenses like wear-and-tear).

-= Offline =-

Many employers let you check your email from time to time. Not so at
this gig. Fair enough, I get it. But there's not even a standalone
machine where you can check it during lunch/breaks.

If I had excess cash I'd probably buy a data plan for my android phone
and be done with it. But I don't. Subbing clobbered my savings and
credit card balances so it will be a few more years of intentional
frugality to get the debt monster back under control with my
regular-but-modest paycheck.

So I bring the Eee netbook for lunchtime email duties. I use
Thunderbird (mail client by Mozilla) for its robust offline abilities,
syncing the mail right before I leave for work and again when I get
home. It's not a total replacement for online email but most of it can
be read and deleted or replied to and synced later. Some of it contains
links or photos that need a net connection to see properly; I move
those to a Gmail folder called "offline" which I look at when I am online.

Theoretically HTML5 will get us offline gmail. Had that with Gears
until google took it offline (ha!) during the transition period.

I also figured out how to email blog entries like this one. The upside
is I can make blog posts for free during lunch. The downside is I don't
see a way to add labels, I can't see my past entries to remember WTH
I've rambled on about before, and I can't easily make links I don't have
memorized. But it works.

posted by offline email

mail to blog gateway

Apparently will let you set up an email/blog gateway.
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