A technical blog entry:
We set off on the 31st like the plan called for.
The trip down to Jewfish Key was excellent. We ran between 4.5 and 6 MPH under
the electric motor until we got into Tampa Bay. I used the Johnson outboard to
keep up with the 4’ waves until we got into the Intracoastal Waterway at Anna
Marie Island. It took us around 3 hours to make the trip.
After setting the anchor in 4’ of clear water, we kicked
back and enjoyed the scenery. We watched as a thunderstorm split before our
eyes and headed northwest and southwest in a V formation around us. I didn't want an afternoon rainstorm to ruin our trip. We saw several rainbows and a
strong contrast of colors between the sky, trees, and buildings in our panoramic
display of God’s glory. It was beautiful and relaxing.
Rainbow to the right!
Storm to the left!
Rainbow to the left!
We watched a dolphin show, which included tail slapping and
acrobatics. SeaWorld can’t take credit for training that into them.
Saturday we had family over for a day on the boat. In the
afternoon we noticed that the lights in the bathroom would not turn on? That
was my first clue that something wasn't right. I went back to check the house
bank for voltage to find that it was near death. After checking the motor
battery bank, I saw that it too was depleted.
Obviously I went into cranking out as much cognitive brain
power, that I still possessed, to sort out what could have went wrong? Questions
about my algorithms kept popping into my head along with questions about
continuing the trip without proper answers.
After several tests, I determined
that a rest was in order. We needed to think rationally, and to do that I
needed to combine all of the facts that I knew at that time, consult God on the
issue, and decide what to do next. Well, His option was somewhat disappointing,
but the right one as it turns out. He recommended that we go back home to debug
the system, and furthermore stay for the summer before heading out on the long
trip.
As usual, when asked, God has all the answers especially if
you know his voice, and getting answers is easy if you listen! The only thing I didn't remember to do was to just pray and have him call some angels down to fix the
problem. I’ll keep that in mind for the next time.
So, after getting back home I emailed tech support for my
controller. I questioned whether it was functioning correctly or not. I assumed
that the battery banks suffered more than I thought in the flood that happened
on the boat while we were in Europe, and that the controller was not
functioning right because of one or more bad batteries in both the house and
motor banks.
MPPT Solar Charger_PCM40
controller
to support
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1.) I have an array of 6- 280 WH solar panels that are hooked up
in series that produces on an average of 122 volts @ approx. 16+ amps.
2.) I have a MPPT Solar Charger_PCM40 controller
3.) I have 6- 12v batteries set up at 24 volts in series:
Powerware series
Eaton 12V 390W Battery
PWHR12390W4FR
Technical specifications
Cells per unit 6
Voltage per unit 12
Capacity 390W @ 15-minute rate to 1.67V per cell @
77°F (25°C)
Weight Approximately 72.75 lb (33 kg)
Maximum 800A (5 sec)
discharge current
Internal Approximately 4 mΩ
resistance
Operating Discharge: 5°F~122°F (-15°C~50°C)
temperature Charge: 5°F~104°F (-15°C~40°C)
range Storage: 5°F~104°F (-15°C~40°C)
Nominal 77°F ± 5°F (25°C ± 3°C)
operating
temperature range
Float charging 13.5 to 13.8 Vdc/unit
voltage Average at 77°F (25°C)
Recommended 39A
maximum
charging current
limit
Equalization and 14.4 to 15.0 Vdc/unit
cycle service Average at 77°F (25°C)
4.) I am running a DC motor A00 4009 DC motor @ 24 volts, which
draws between 20 and 30 amps while running.
280WH * 6 = 1680 WH -- PCM 1000WH?
24 volts * 30 = 720 WH
Q. 1) Shouldn't I be able to theoretically power via solar power
in a draw and replacement give and take with the solar battery combination?
Q. 2) I can set my controller parameters (AH, BATT, etc.) and
save them, but cannot get the controller to go back to the standard display
even after holding down the Step4: key? The green battery light in on and not
flashing.
Q. 3) If one or more of the batteries were bad or depleted,
could that make the controller not respond correctly?
Q. 4) If, I just used one set of 24 volt 100AH batteries, would
the solar array/controller/battery combination run the above motor @ 24 volts,
and no more than 30 amps?
Support Team, MPP Solar Inc.
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to me |
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Hello,
Please see our reply below in blue.thanks
Best regards,
-James Ko, MPP Solar Inc.
PV: 280w*6=1680w, and motor is 720w, so theoretically it would
be ok. However, motor loads tend to require high surge current during
start-up which can be up to 7~8 times the continuous, depending on its
design.
So if you look at it this way it is possible that the 1680w of
PV isn't sufficient to get it started, but the reserve in the batteries would
take care of this. However this is just a speculation as I'd suggest the
start-up current be measured.
Another issue of consideration is that a battery acts as a
stabilizer in any power source and ensures a load can be powered properly
without frequent interruption. PV is an extremely unstable source
of power (depending on where you are) - a piece of cloud, falling leaves,
shading, dust, etc... can all contribute to a sudden drop in power, which can
cause a stop on your load.
Q. 2) I can set my controller parameters (AH, BATT, etc.) and
save them, but cannot get the controller to go back to the standard display
even after holding down the Step4: key? The green battery light in on and not
flashing.
If your setting can be saved it should be ok. Did you try
pressing the function key down a bit harder? By the way I just realized
you're referring to the pcm4048 (we have another series PCM40CX) which is a
40amp/1000w model, so connecting 1680w of array is frankly a bit of a waste of
PV, since it's limited by the 1000w max output so you have about 680w of
untapped potential which I'd recommend putting through another charger to
contribute power.
Q. 3) If one or more of the batteries were bad or depleted,
could that make the controller not respond correctly?
Yes, it's possible. One or more bad batteries can bring
down the overall voltage, rendering the system voltage to be read differently
and falls out of the battery volt range deemed acceptable by the controller
Q. 4) If I just used one set of 24 volt 100AH batteries, would
the solar array/controller/battery combination run the above motor @ 24 volts,
and no more than 30 amps?
Every battery should have a specification curve which tells you
the discharge time of a battery based on the level of current draw. For a 100Ah
battery it usually means 20 hours of draw time at a 5amp current (hence 100Ah,
if it's a C/20 rating) and so if your load draw is 30amp, the time the 100Ah
can last will reduce dramatically.... this would be a guess, but I think
perhaps just 1.5~2hours? But the power from the PV array should be able to
balance out in time with the extra 10amp from the 40amp controller if not
obstructed.
I will go down to the boat today to check the battery bank,
and try “pushing down harder” on the Step4: button to see if the LCD attributes
return to normal. Then I will take 2, if I have 2 good ones, of the batteries
in the motor bank to test the PCM controller. I’ll put them in series to create
the 24 volt system my motor runs on. Then on the house bank I will do the same,
but I will only need 1- 12 volt battery for that.
I did not mention to the PCM controller tech that I have
another solar controller for the house bank that contributes 24 volts at 30
amps to it along with another controller attached to the wind generator that
can push up to 450 watts into the house bank. In fact, in my estimation, we were
running on wind generator power all weekend without knowing it. The lights went
out when the wind died down, and the generator quit spinning.
Looks like we will be here for scallop season at Homosassa Springs this July!
