Thanks for all the input.
This is for field trials, in very rural/sparse
(fiber is not cost effective) and forested/hilly
(LOS wireless is not an option) PA or possibly
MN, so although there's pretty limited sunshine
and a generator could be put in place for periods
of extended cloud cover, we're probably looking
at (hopefully) just needing a couple days of battery runtime.
For backhaul we were just going to use a Ubiquiti
PtP we have laying around, which is 24v but
otherwise I think most gear we would use for
production is 48v. So a 48v system seems to make
the most sense. Trade-offs between 12v/24v/48v
storage was my main interest. Such as monitoring
for weak/dead batteries in multi-battery
configuration, losses in up/down converters, etc.
So basically this is to get some real world
experience with solar systems and TVWS (initial tests have been positive).
Thanks.
At 02:32 PM 1/12/2021, you wrote:
Yeah, in this case, it's easy to access, and I
needed to get it online quick, so I just threw
what I had on there. If it was a difficult site to access, I wouldn't do that.
Once you get up to a certain size of system, it
probably is going to make sense to go the
generator route with smaller batteries. Those
batteries are eventually going to need to be
replaced, and the difference might pay for a
generator, and give you better reliability.
On Tue, Jan 12, 2021 at 1:22 PM Chuck McCown via
AF <<mailto:af@af.afmug.com>af@af.afmug.com> wrote:
To me, it all depends on accessibility. If you
can get there with a generator you can make do
with smaller batts. Better yet put in a small
propane powered generator with either a low
voltage relay for starting or telemetry for starting.Â
Â
From: Mathew Howard
Sent: Tuesday, January 12, 2021 12:15 PM
To: AnimalFarm Microwave Users Group
Subject: Re: [AFMUG] Solar/Battery for Micro-PoP
Â
Since we're talking about a relatively small
system, I would base whether to do a 24v or 48v
system on what the majority of the load is going
to be. If it's going to be like 70% 24v gear,
I'd go with 24v, but otherwise, I'd probably lean towards 48v.
Â
Bill's numbers look about right for what you'd
want for a system that you aren't going to need
to worry about. If you're not opposed to the
risk of maybe occasionally needing to go out and
swap out some batteries in the middle of winter,
and that sort of thing, it's possible to do it
with a smaller system. We have a micropop with a
roughly 10-12 watt load running on 200 watts of
solar panel and ~5KWH of lead acid batteries
(that happened to be what I had on hand at the
time... there wasn't any logic involved in
picking that size)... so far it seems to be surviving the Wisconsin winter.
Â
On Tue, Jan 12, 2021 at 12:55 PM Bill Prince <part15...@gmail.com> wrote:
If your load is 50W, then you need to deal with ~~ 1.2 KWH of energy
usage per day (50*24).
We don't know your latitude, or location, so you will have to plug in
whatever solar values are typical for your area. However, a good rule of
thumb for mid-latitude areas is to have enough battery for 10 days of
operation without sun. So you will need about 12KWH of battery storage.
If you're using lead acid batteries, double that for 24KWH of storage.
Then you will need enough solar for you to recover that in one or two
days. For example, if you have 1200 watts of solar, you can typically
expect to get back 4.8KWH per day (5 hour day at 80%).
A 48V system would be the most efficient. It will require smaller wires,
and converting from 48->24 is more efficient than the other way around.
Separately, I would suggest to examine your sanity for thinking you
might be the only one in the US to make TVWS actually work.
bp
<part15sbs{at}gmail{dot}com>
On 1/12/2021 10:42 AM, D. Bernardi wrote:
>
> Hi,
>
> I'm considering some fixed wireless (TVWS) trials and/or the ability
> to deliver temporary service where there's no available power source.
> I've done some basic solar system calculations (and there are plenty
> of calculators) but I'm looking for some real world pointers from
> those that have deployed off-grid micro-PoPs.
>
> DC only, no inverters required. We may need 24v PoE and 48v PoE so
> would a 48v system with step down to 24v be more efficient than 12v or
> 24v with a step up? Other trade-offs to consider for 12v/24v/48v
> storage systems?
>
> I don't have actual load measurements yet but at this point I'm
> currently sizing for a 50w load. The base station and backhaul radios
> combined should be ~ 30w.
>
> Thanks,
> Dave B.
>
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