[ANSS-netops] solar power problems

[Mitchell M Withers (mwithers)]

Here is a snippet from a recent report from a visit to an example station with a reftek, three S-13's, and an episensor.  Stations vary of course and we do use low voltage cutouts at every station (fancy ones that cut out the transmitter first, then the DAS and everything else if the voltage continues to get lower).

"The new battery banks, when installed were at 12.95 and 12.98. The total station draw is exactly 600ma (checked continuously for about three minutes). I did a quick calculation of 4 batteries at 96AH each, 384/.6 = 640/24 =26.6 days. This calculation would assume no solar charge, but does not take into account reduced battery capacity due to cold temperatures."

The panels at that particular station were supplying about 700ma together on an overcast day and are being replaced with bigger panels this week.  Of course one solution is more battery and more solar at every station along with more frequent refreshing of batteries.  But that gets expensive and time consuming so I was fishing to see if anyone is doing something creative. (e.g. wind or hamster wheels).

Mitch

Center for Earthquake Research and Information (CERI)
University of Memphis                Ph: 901-678-4940
Memphis, TN 38152                   Fax: 901-678-4734


________________________________________
From: Philip Crotwell <crotwell at seis.sc.edu>
Sent: Monday, January 5, 2015 7:50 AM
To: Mitchell M Withers (mwithers)
Cc: anss-netops at geohazards.usgs.gov
Subject: Re: [ANSS-netops] solar power problems

Hi

How did you come up with your 25 day figure? Can you put some numbers
on power input and output?

We use two 105 amp-hour batteries per station, where the load is about
1/2 an amp. That gives me about 17.5 days theoretically, but my
understanding is that you never want to discharge batteries anywhere
near their rating as they can be damaged by high discharges. So maybe
worry less about age and more about installed capacity, ie double the
battery and replace them half as often.

We also, because of the cell modems, can monitor the battery voltage
over time, we have a cron job to ping the cell modem once an hour and
ask it what the input voltage is. For example here is the last few
days at one station. You can definitely tell the difference between
sunny days and rain, and we get a heads up if the power is getting low
and can do something before the station goes down.
http://eeyore.seis.sc.edu/earthworm/status/HAW_last720.png

Here is another station that we are becoming worried about, looks like
I might get to go on a road trip soon!
http://eeyore.seis.sc.edu/earthworm/status/CASEE_last720.png

Philip

On Sun, Jan 4, 2015 at 9:07 AM, Mitchell M Withers (mwithers)
<mwithers at memphis.edu> wrote:
>
> Many of our stations run on battery and solar and that normally works well.  We have a routine battery replacement cycle to make sure they don't get old.  Theoretically, we should be able to run with zero solar for about 25 days.  But this has been an unusually dreary winter in the southeast and we haven't had much sun for the past two months or more.  I'm wondering what others do in areas with limited sunlight to power stations that don't have AC available?
>
> Mitch
>
> Center for Earthquake Research and Information (CERI)
> University of Memphis                Ph: 901-678-4940
> Memphis, TN 38152                   Fax: 901-678-4734
>
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