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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