Posted by Jim Wilkins on April 2, 2019, 3:01 pm
<ads> wrote in message
No such luck here, Craig's List is dry and the local electronic
surplus store has a waiting list for large AGM batteries. NH is both
relatively rural and very high tech.
I've held that and other medical technician jobs. Government aid and
heavy regulation significantly distort that industry beyond what
appears logical. Look at the cost of EpiPens or an ambulance trip.
I got ten years from the truck's OEM battery and 17 from the
replacement that I took better care of, until its current into a
Harbor Freight carbon pile tester dropped too close to the starter's
winter demand. The OEM battery from my 2000 car still tests at 50A. I
top off my battery collection about monthly with the solar system and
a metered adjustable LM350 regulator I built.
Keeping old vehicles runs in the family. The last time I visited
relatives in Alabama one still drove a 1935 pickup.
My garden tractor's battery is an Autozone Duralast U1 dated 10/13
that a neighbor bought and gave me a few years later when it wouldn't
start his mower in the spring. I added it into the monthly top off
program and yesterday it still started my tractor. It appears that
once they have gone flat they can be restored with higher DC voltage
but need frequent recharging, which the friends who give me old
batteries don't want to bother with.
AFAIK DC works as well as pulse desulfators, but requires more user
knowledge and attention and a metered variable lab power supply (or
homebrew). I learned how as the battery tech at Segway.
Old 12V 18AH AGMs, the largest I can usually find, don't last nearly
as long with the same treatment. Some Powersonics still had 1/4 ~ 1/2
capacity after 10 years, others have failed by sulfation or a dead
cell in 5 or less, and 16~20V desulfation doesn't help them.
Posted by Jim Wilkins on March 31, 2019, 3:45 pm
<ads> wrote in message
My new 4.3 cubic foot Magic Chef dissipates heat through the shell
like that, so I can't add insulation. However a KAWez recorded its
electricity cost this winter as only $.70 per month, at $.182 per
Posted by ads on April 1, 2019, 6:20 am
On Sun, 31 Mar 2019 11:45:03 -0400, "Jim Wilkins"
I have a 4.4 cu ft Kenmore 99783 "dorm fridge" runs at 55 watts for
about 5.4 hours a day at 78F or about 330WH/day. At $.0768/KWh, that
works out to about $.76/month so the performance of the two fridges
is similar (9.9KWh/month for mine, 9.3KWh for yours). The small
fridge is my place to keep heirloom seeds - and the backup fridge for
leftovers when we have family here for holidays (Thanksgiving,
Christmas). In a long term grid outage, it would be the primary
fridge after things from the larger fridge and freezer were used up.
Posted by Johnny B Good on April 2, 2019, 2:47 pm
On Sat, 30 Mar 2019 08:12:55 -0500, ads wrote:
If you're trying to describe the flat topped peaks, typical of
utility power worldwide, that's just the result of all the countless
smpsus used in TV sets and desktop computers and USB wallwart chargers
and laptop charging bricks and... well, let's just say there's a hell of
a lot of mains powered kit that rectifies the mains supply to generate
whatever dc voltages are needed (whether it be directly at full mains
voltage or on the low voltage secondary of a stepdown isolating
transformer such as an old school battery charger.
Yes folks! Even ancient 70 year old battery chargers assaulted the mains
supply with narrow conduction angle rectified current pulses which causes
this 'flat topping' effect. It was just that, back in the day, such loads
were in the minority.
This flat topped appearance of the mains supply waveform has been
present on utility supplies for well over three decades to my knowledge
and probably existed to a lesser degree ever since the whole world and
their dog started watching TV as a national pastime.
The advent of the home computer and subsequent electronic gadgetry has
no doubt exacerbated this situation to the point where this "Signature
wave trace" can now be relied upon to identify when you're running off
utility power rather than from a UPS or standby generator source.
 You may notice a downward slope on the 'flat tops' on the positive
peaks of each cycle of mains voltage and mirrored in the negative peaks.
This is the high pass filtering effect when using the AC coupling option
on a 'scope or else seen in audio recordings made from a low voltage
mains transformer winding (6.3v heater voltage winding attenuated down to
the hundred millivolt level to avoid overloading your sound card's line
input buffer, for example).
Selecting DC coupled, will reveal the true wave shape, an option I
didn't have with my 5MHz BW boat anchor CRO nor with my CoolEdit Pro
recordings of mains voltage supplied by my generator and pure sine wave
UPS to compare against the utility supply, until I finally treated myself
to a brand new DSO some five months ago.
Johnny B Good
Posted by Jim Wilkins on April 2, 2019, 3:22 pm
There are also spikes from SCR and Triac switching which can be
anywhere including near the zero crossings. I had trouble with them on
industrial park electricity when trying to construct a low phase noise
line-synched PLL reference oscillator.