Controller or batteries?

A technical blog entry:

We set off on the 31^st 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

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. to me

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!