My electric car loses significant range at temps below 35F and as a double
whammy, will not accept a full charge at low temps either.
Lead acid work at low temps but if they get too far discharged they will
freeze. Gates Cyclons were advertised to be able to be fully charged and
discharged when frozen.
From: Mathew Howard
Sent: Thursday, August 17, 2023 2:13 PM
To: AnimalFarm Microwave Users Group
Subject: Re: [AFMUG] battery nerd question
Yeah, temperature is the main problem I'm seeing with going to lithiums. I can
throw an SLA battery in an unheated box at our towers and it's going to work
good enough, even in the middle of winter, but the minimum charging temperature
for LFP batteries is 32F, which we're going to be below for a good part of the
year.
On Thu, Aug 17, 2023 at 3:08 PM Bill Prince <part15...@gmail.com> wrote:
Things have evolved. You can get LFP batteries for "almost" the same price as
lead acid. Sometimes less even. They occupy less than half the space as lead
acid, and will last at least twice as long. There is the issue of temperature
sensitivity and they will need help for extremely cold environments.
bp
<part15sbs{at}gmail{dot}com>On 8/17/2023 12:36 PM, dmmoff...@gmail.com wrote:
Ooh What lithium batteries are we talking about?
Last time I checked (a number of years ago), it was around 5x the $/Wh to
buy Lithium.
From: AF mailto:af-boun...@af.afmug.com On Behalf Of Mathew Howard
Sent: Thursday, August 17, 2023 10:51 AM
To: AnimalFarm Microwave Users Group mailto:af@af.afmug.com
Subject: Re: [AFMUG] battery nerd question
Well, right. It doesn't scale well, because battery costs and space
requirements will quickly become a problem. Batteries don't last forever, so
you have to factor in replacement costs too, which will be a significant
ongoing cost for a larger system. I'm pretty sure that lithium batteries would
be cheaper long term now, since they should have a lot longer life span and the
initial cost isn't a lot higher, but then heating is required, which means you
need more power.
On Wed, Aug 16, 2023 at 7:02 PM <dmmoff...@gmail.com> wrote:
That’s building strictly for a 20W load though. Building for a tiny load
does make the costs easier. But if you wanted a second AP, bigger backhaul, or
anything else you can’t do it without growing the whole power system
proportionally.
Steve was talking a 50W load today. The real high end hardware now is
using a lot of signal processing either to reassemble useful data out of
garbage or for beam steering, or both. So you end up needing 100-150W for an
AP. You’d be hard pressed to find a licensed backhaul under 35W, and most of
them are 50W+. We could say we won’t deploy that equipment….but building for a
20W load takes the choice away.
A 20A 240v circuit is 4800W. Or a 20A 120V circuit is 2400W. Even 2400W
would power almost any WISP deployment. Building solar to handle any load you
might have is expensive, and building for only low power handcuffs you.
You do your thing your way, no judgement. If it’s working for you then
it’s good, but I can’t see myself going that direction.
-Adam
From: AF <af-boun...@af.afmug.com> On Behalf Of Mathew Howard
Sent: Wednesday, August 16, 2023 5:01 PM
To: AnimalFarm Microwave Users Group <af@af.afmug.com>
Subject: Re: [AFMUG] battery nerd question
I'm at about the same latitude as you. My experience is that having extra
battery capacity is more helpful than oversizing the solar panels, so I'd
probably go with Chuck's numbers for batteries if I was putting something
together now, and solar panels are cheap now anyway, so figure 400 watts (if
mounting space allows for it, which could be an issue if we're trying to fit it
on a pole).
A quick check on Amazon shows 100ah SLA batteries for $160, so 6 of those
would give me 7200 watt hours, for just under $1k. At $1500 (which is mostly
just adjusting battery and panel sizes from where I started at $1k), I'm right
in line with Chuck's estimate, aside from the battery costs.
On Wed, Aug 16, 2023 at 3:33 PM <dmmoff...@gmail.com> wrote:
I end up closer to Chuck’s estimate. In Southern or Central NY State
I’m 2 degrees north of Salt Lake City. 42N
What’s your latitude?
From: AF <af-boun...@af.afmug.com> On Behalf Of Mathew Howard
Sent: Wednesday, August 16, 2023 4:11 PM
To: AnimalFarm Microwave Users Group <af@af.afmug.com>
Subject: Re: [AFMUG] battery nerd question
Yeah, that's what I'd do in a difficult to access location. I did a
site like that here (Wisconsin) with 200 watts of panel (I think the actual
load is around 15 watts, so a bit more than 10x), and ~4kwh of battery. It had
some issues in January a couple years, but I attributed that more to using
cheap flooded deep cycles, rather than not enough capacity. With AGMs, it's
gotten through the last couple of winters without issues. 4kwh of AGMs can be
had for around $800, last I checked. Probably looking at closer to $1500 when
you add in enclosures and mounts, but some of that is replacing parts that are
needed with AC power anyway (smaller enclosure, backup batteries, power
supply), so that offsets it a bit.
On Wed, Aug 16, 2023 at 2:50 PM Chuck McCown via AF <af@af.afmug.com>
wrote:
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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