Don't buy 12v lifepo4 batteries for series use, it's much better to buy
a 24v or 48v battery as it will have one BMS and keep balanced.
https://signaturesolar.com/shop-all/batteries/
<https://signaturesolar.com/shop-all/batteries/>
Some of the main players are signature solar, trophy battery, and a
bunch of others look at Will prowse solar on YouTube and you can see
reviews of all of the different 48 volt batteries.
On Thu, Aug 17, 2023, 1:03 PM Mathew Howard <[email protected]
<mailto:[email protected]>> wrote:
LiFePO4. There are a few different ways you can go with that though.
You can get something like these:
https://www.18650batterystore.com/products/eve-lf280k
<https://www.18650batterystore.com/products/eve-lf280k> which I
think actually comes out slightly cheaper than SLA/AGM, but then you
need a separate BMS, or you can get something like this:
https://www.ebay.com/itm/166234057827
<https://www.ebay.com/itm/166234057827> which is made to be a drop
in replacement for lead acids, and has a built in BMS.
On Thu, Aug 17, 2023 at 2:37 PM <[email protected]
<mailto:[email protected]>> 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 <[email protected]
<mailto:[email protected]>> *On Behalf Of *Mathew Howard
*Sent:* Thursday, August 17, 2023 10:51 AM
*To:* AnimalFarm Microwave Users Group <[email protected]
<mailto:[email protected]>>
*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 <[email protected]
<mailto:[email protected]>> 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 <[email protected]
<mailto:[email protected]>> *On Behalf Of *Mathew Howard
*Sent:* Wednesday, August 16, 2023 5:01 PM
*To:* AnimalFarm Microwave Users Group <[email protected]
<mailto:[email protected]>>
*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 <[email protected]
<mailto:[email protected]>> 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 <[email protected]
<mailto:[email protected]>> *On Behalf Of *Mathew
Howard
*Sent:* Wednesday, August 16, 2023 4:11 PM
*To:* AnimalFarm Microwave Users Group <[email protected]
<mailto:[email protected]>>
*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
<[email protected] <mailto:[email protected]>> 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
<[email protected] <mailto:[email protected]>>
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 <[email protected]
<mailto:[email protected]>> *On Behalf Of
*Steve Jones
*Sent:* Tuesday, August 15, 2023 10:27 AM
*To:* AnimalFarm Microwave Users Group
<[email protected] <mailto:[email protected]>>
*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
<[email protected]
<mailto:[email protected]>> 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:[email protected]
<mailto:[email protected]>] *On Behalf
Of *[email protected]
<mailto:[email protected]>
*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:*[email protected]
<mailto:[email protected]>
<[email protected]
<mailto:[email protected]>>
*Sent:* Tuesday, August 15, 2023 6:56 AM
*To:* 'AnimalFarm Microwave Users Group'
<[email protected] <mailto:[email protected]>>
*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 <[email protected]
<mailto:[email protected]>> *On Behalf
Of *Steve Jones
*Sent:* Monday, August 14, 2023 9:57 PM
*To:* AnimalFarm Microwave Users Group
<[email protected] <mailto:[email protected]>>
*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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