Using my historical rules of thumb for off grid, snowed in mountain
top location for a 20 watt load I would do the following that has
never failed me:
Load X 20 so 400 watts of panel. So less than $200 these days.
2 weeks of battery autonomy.
20 x 24 x 14= 6720 watt hours. $2K of batts
Plus enclosures, mounts, charge controllers.
$2500 and it will never go down in the winter. At my Utah latitude
on top of Utah mountains.
*From:* Mathew Howard
*Sent:* Wednesday, August 16, 2023 1:07 PM
*To:* AnimalFarm Microwave Users Group
*Subject:* Re: [AFMUG] battery nerd question
It depends on how much stuff you're trying to run. A minimal
micropop can be done with less than 20 watts of load (single AP and
backhaul). I can put together a solar setup for around $1000 that
will power that.
On Tue, Aug 15, 2023 at 12:50 PM <dmmoff...@gmail.com> wrote:
I can save you the suspense. If you have access to electric
that’ll
be cheaper than solar. The problem is the need to run 24/7. You
have to design around the December-January months. I’m in NY
State,
and at our latitude we only get a few hours of average production
per day during those months. And obviously if it’s snowing for a
week you need to be able to ride through that on mostly battery
power. Even with a modest load it takes a silly amount of panels
and batteries to stay up 24/7 in the winter. More than you’d ever
be allowed to put on a utility pole. ____
____
Talk to your electric co about the smallest service you can get.
Explain what you’re trying to do and that your max load is very low.
____
NYSEG normally doesn’t do less than 100A, but they made an
exception
and let us do 60A. You need a meter can, a service rated panel, a
conduit up the pole and a weatherhead. Then you either have an
outdoor outlet, or have an outlet inside your enclosure. You’ll
want the smallest service they’ll let you do because of the wire
size on the service cable. A 20A (if they’d allow it) would only
need a 12/3 with ground, and that’s up to 4800 Watts (240x20) so
it’s still more than you’d ever need. A 12/3 is way cheaper
than a
100A service entrance cable.____
____
My figure is 8 years old, and obviously there’s been inflation
since
then, but I went to the same contractor who does electric installs
for the cable company and they quoted me about $1000. Even if it’s
3x that for you today you’d still never beat that with a solar
installation even if they’d let you do it. And I’m not some
knee-jerk anti-solar lunatic, I’m just saying I’ve run the numbers
and it doesn’t add up. People do it when they’re off grid, or
when
the electric service is unreliable in the area, or sometimes just
for the PR/marketing power of being “solar powered”. Those are all
fine reasons, but doing it for cost savings isn’t going to work
out.____
____
-Adam____
____
____
*From:* AF <af-boun...@af.afmug.com> *On Behalf Of *Steve Jones
*Sent:* Tuesday, August 15, 2023 10:27 AM
*To:* AnimalFarm Microwave Users Group <af@af.afmug.com>
*Subject:* Re: [AFMUG] battery nerd question____
____
we have a dozen or so, but are looking at pole mount micropops (our
own poles). We are losing a grain elevator site because they
decommissioned the elevator and theres no real options for the
customers in some of the areas. Im just trying to get to something
we can get solar power with enough battery to last through
overcast.
So Im calculating per battery runtimes, then will look at number of
batteries we would need to survive vs paying for a ROW meter vs
losing the customers. Just have to get to the cost per customer to
retain them and the benefit gained per pole____
____
____
On Tue, Aug 15, 2023 at 8:53 AM Brian Webster
<i...@wirelessmapping.com> wrote:____
How many of the batteries do you have? Do you need any voltages
other than the 48 volts? If you have 4 batteries and only need
48 volts then wire them in series and not have to deal with the
converter.____
____
Thank you,____
Brian Webster____
____
____
*From:*AF [mailto:af-boun...@af.afmug.com] *On Behalf Of
*dmmoff...@gmail.com
*Sent:* Tuesday, August 15, 2023 6:59 AM
*To:* 'AnimalFarm Microwave Users Group'
*Subject:* Re: [AFMUG] battery nerd question____
____
*You’re around C/30 which should be on the high end /of
capacity/. ____
Lower load usually means a little extra capacity out of the
battery. I realized that sentence might have been
ambiguous.____
____
____
*From:* dmmoff...@gmail.com <dmmoff...@gmail.com>
*Sent:* Tuesday, August 15, 2023 6:56 AM
*To:* 'AnimalFarm Microwave Users Group' <af@af.afmug.com>
*Subject:* RE: [AFMUG] battery nerd question____
____
You can do the whole thing in Watts.____
____
12V * 150ah = 1800 Watt-hours____
1800Wh / 50W = 36 hours____
____
If they’re telling me 95% efficiency, I’d assume 50W out needs
53W in (50 / 0.95). ____
There’s usually an efficiency curve for the device based on
load
and temperature so it wouldn’t be 95% in all circumstances.
Your
system should be drawing less than 5A off the battery, and if
your multimeter has a 10A fuse like most do, then you could put
the meter in line and actually measure the amperage before and
after the converter. Then you’d know for sure.____
____
And the battery’s total capacity will have a curve based on
C-rate so there’s some variability there too. Usually it lasts
longer when you’re drawing lower amperage. You’re around C/30
which should be on the high end. ____
____
Age and maintenance of the battery affect runtime as well.
If I
want 6 hours of runtime then I plan Ah for 12 hours runtime.
When my batteries are halfway toasted I’m still getting useful
life out of them.____
____
____
*From:* AF <af-boun...@af.afmug.com> *On Behalf Of *Steve Jones
*Sent:* Monday, August 14, 2023 9:57 PM
*To:* AnimalFarm Microwave Users Group <af@af.afmug.com>
*Subject:* [AFMUG] battery nerd question____
____
Just trying to cipher runtimes____
I have on hand 150ah 12 volt batteries, so thats what id be
looking to use.____
Excluding the conversion loss of a 12v to 48v step up converter
is the math correct here?____
12v 150ah=1800 watt hours
1800 watt hours at 48v = 37.5ah
50 watts of radio running 48v = 1.04 amps
37.5ah @ 1.04 amps = 32.77 hours runtime____
____
does a step up that claims 95% efficiency mean 95% of the watt
hours?____
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