remote fish tracking system

System

I am using a 65W solar panel and a bank of 3 deep cycle marine batteries to power two dataloggers and antennas that track fish in a remote site in Maine. The batteries are 24 and 27 group (around 100 amp hours) from Napa and Walmart. They are connected in parallel so I have a 12V system with combined (~300) amp hours. I know that one of the antennas draws about 0.5 amps. Not sure about the other but I guess it is similar or less.

I have trouble keeping it running. In fact, I still have to change out batteries about every 7-10 days and bring them back to the office and charge them. Many times the voltage is well below 12V, which is probably not good for the battery life (this may be part of my on-going problem...)

So, I would like to know if anyone has any insight into what changes I could make in my battery/solar panel design to power this system 24/7.


Tim

BB.

Re: remote fish tracking system

If your load current varies over time, you might want to measure it with a DC Amp*Hour / Watt*Hour meter like one of these.

Using PV watts, derating of 0.52 (end to end efficiency), fixed array, 1 kW (1,000 watts--even number, smallest PV watts accepts), for Caribou Maine

"Station Identification"
"City:","Caribou"
"State:","Maine"
"Lat (deg N):", 46.87
"Long (deg W):", 68.02
"Elev (m): ", 190
"PV System Specifications"
"DC Rating:"," 1.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 0.5 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 46.9"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","12.2 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 3.36, 58, 7.08
2, 4.34, 67, 8.17
3, 5.23, 86, 10.49
4, 5.75, 89, 10.86
5, 4.99, 74, 9.03
6, 5.09, 71, 8.66
7, 5.15, 73, 8.91
8, 4.99, 72, 8.78
9, 4.26, 61, 7.44
10, 3.45, 53, 6.47
11, 2.38, 35, 4.27
12, 2.73, 46, 5.61
"Year", 4.31, 784, 95.65

Lets say that each unit uses 0.5 amps... So for 24 hours:

• 1 amp * 24 hours * 12 volts = 288 WH per day (based on

Worst month is November with 2.38 hours of full sun equivalent per day:

• 288 WH per day * 1/0.52 derating * 1/2.38 hours of sun per day = 233 Watts Minimum solar panel

So, for winter you need, at the very least, 233 watts of solar panel just to keep even.

Or, you will need an alternative source (generator, swap batteries, etc.) during the dark times of the year.

Excluding the 3 months of the year with the lowest sunlight, that gives you October at 3.45 hours of sun for the other 9 months of the year:

• 288 WH per day * 1/0.52 derating * 1/3.45 hours of sun per day = 160 Watts Minimum solar panel

Anyway--that is how I would do the calculations. If you need this to be unattended--you are seriously going to need to look at >233 watts of solar panels.

Also, other things to think about:

• What kind of solar charger do you have? You should look at one that has a remote battery temperature sensor to better charge your batteries and account for the very wide swing in temperatures. For cold regions (snow on the ground), a MPPT charge controller may give you 10-15% or so more energy during the winter. Also, if you get >> 100 watt solar panels, you will probably need a MPPT type charge controller as most panels are >> 17.5 volts Vmp that is used with PWM on a 12 volt battery bank.
• Look at AGM batteries. No watering needed, much more freeze tolerant. More efficient (~90% efficient vs ~80% for flooded cell).
• A Battery Monitor (Victron Energy also makes a nice unit) may be helpful for you to evaluate the charge of your battery bank at a glance. For AGM/sealed batteries, you cannot measure specific gravity.

-Bill

System2

Re: remote fish tracking system

This is very helpful, thanks Bill.

I have a Kyocera 65W hooked into the battery bank. Can I simply add a second solar panel into the system? I have another 65W panel at another site. Would that improve the battery longevity significantly?

BB.

Re: remote fish tracking system

Probably yes. What kind / model of solar charge controller do you have?

With your current setup, you probably need to change the battery bank every one to two years. Using true deep cycle batteries would be better, however if you take them to dead every few months--spending lots of money on high quality batteries may be difficult to justify.

Looking at ways to reduce power use, conservation, may be helpful too.

-Bill

dwh

Re: remote fish tracking system

130w would still be below break even according to Bill's calcs. That's in the summer, in the winter it would FAR below break even.

Does any shade hit the solar panel? ANY shade, even on one small corner will take it down to virtually no power.

System2

Re: remote fish tracking system

I don't have a solar charge controller in the setup. It was a package deal from the radio telemetry company(Advanced Telemetry Systems) with a Kyocera KC65T, 65 Watt 12 Volt Nominal Solar Panel. The panel connects directly to the battery bank. Should I have a controller?

I will have to double check on the shade issue. I know one panel sits in the the top of a tall fir tree and has a clear view to the south. The other panel at the other site is low but on the north side of the river. So there is about 100' of clear view to the south although there were some alders trees near the panel.

Thanks

BB.

Re: remote fish tracking system

If you do not have enough solar power for the system, then you really don't need a solar charge controller. The job of the controller is to keep the battery from being over charged. If you do add enough solar panels / reduce loads -- then you will need some sort of charge controller to protect your batteries (and equipment from over voltage).

Simple charge controllers are not expensive ($100-$300). The "expensive" ones are >$500 each (probably one maximum for your system).

Solar panel wise, it would be very nice if the solar panel is "shade free" from at least 9amp to 3pm. Solar PV panels simply require full shade free sun to charge the battery bank (as your system is currently configured). If there is any shading at all the output will be significantly reduced. If the panel is in mottled shade--it will produce virtually no useful output.

You only know he estimated load for one of the two antenna systems... If the average load is 1 amp at 12 volts for the pair:

• 300 AH / 1 amp = 300 hours of storage (until the batteries are dead)

For your solar panel, it is probably 65 watts at 17.5 volts or so...

• P=V*I
• I=P/V= 65 watts / 17.5 volts = 3.71 amps

The solar panel for this time of year would collect 2.38 hours of sun per day:

• 3.71 Amp*Hours * 2.38 hours of sun (November) = 8.83 Amp*Hours per day of solar power

So, the estimated life of the battery bank would be:

• 1 AH of load * 24 hours = 24 AH per day energy usage
• 300 AH * 1/(24 AH per day load - 8.83 AH per day of solar) = 19.8 days to dead

Now, in real life--we really don't want to see the batteries cycled below 50% state of charge per day, and you should never discharge below 20% state of charge (80% state of discharge)--Below that, you run the risk of permanently damaging the battery bank.

And operating the battery bank for days/weeks/months below ~75% state of charge will dramatically shorten the life of the battery bank (batteries sulfate and lose capacity if they are not promptly recharged when cycled below 75% state of charge). Just a guess, but you only expect months or 1 year of battery life of life from a usage cycle when operated in your current setup.

Depending on your system's life (only operating a few months of the year for the next one or couple spawning cycles--for example)--then why not continue as you have been.

If the system is intended for 24x7x52 weeks per year for years/decade to come--then you probably need to figure out a more cost effective solution.

For example, say you go out once a week to recharge the battery bank with a portable genset:

• 300 AH * (7 days / 19.8 days of capacity) = 106 AH per week deficit (for November)

Battery rate of charge from 5-13% (rule of thumb for flooded cell):

• 300 AH * 0.13 rate of charge = 39 Amps

Get a good quality 40 amp charger and a Honda eu2000i genset:

• 106 AH * 1.20 (20% extra power to recharge) * 1/40 amp = 3.18 hours

Add at least 2-4 hours at gradually reduced (tapering / reducing current) until battery is recharged.

So, 5-7 hours per week plus 2 gallons of gasoline per trip... and you have 24x7 power for your setup.

In the summer months (4.26 hours of sun or more):

• 3.71 Amp*Hours * 4.26 hours of sun (November) = 17.1 Amp*Hours per day of solar power
• 1 AH of load * 24 hours = 24 AH per day energy usage
• 300 AH * 1/(24 AH per day load - 17.1 AH per day of solar) = 43.5 days to dead

Go out every and recharge every 2-3 weeks for 8 months of the year.

Or, same as above but skip the generator, bring out a second set of charged batteries and recharge the first set back at the shop.

I would suggest:

• Measure the loads. Need to know Amp*Hours / Watt*Hours used per day. If the power used over a 24 hour period (sometime more power, sometimes less) then you a DC Amp*Hour / Watt*Hour meter to measure the energy used over time.
• Define your service interval (week/month/year)
• Define your system life (1 season, one year, years to come)
• Define your costs (more panels in field, use cheap batteries and replaced often, use better batteries and more solar panels, vs more time in field with existing setup for recharging/swapping batteries, etc.).
• Do a couple paper designs and weigh costs vs security (Vandals/thieves) vs time of site. See what best meets your needs.

-Bill

PS: You should also know the length of wire run and gauge of wiring. Long wire runs, small gauge wire, operating at 12 volts nominal can further reduce panel output because of excessive wire resistance and voltage drop.

Also, the other use of a solar charge controller is to reduce self discharge by the solar panels at night... For a 12 volt battery bank, the self discharge of the panels is not all that great. For a 24 or 48 volt battery bank, you really do need a blocking diode, or a real charge controller (recommended).