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TopTierLandscape

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Posts: 5
Reply with quote  #1 
Hi guys,
I am new to your forum and found it a great place for off grid info. I am trying to run a 230v 2hp 10.7 amp on each leg well pump on a 24v Mpp solar 4024 inverter. The problem that I am having is that the inverter keeps on resetting after a few minutes due to low voltage. It runs fine for about 15 minutes, then starts resetting.

I am puzzled as I’m using 4-6v deep cycle full river AGM 224 amp batteries. They are ran in series then parallel. As of right now- we are generating approx 1300 watts from 5 Canadian solar 300w panels.

I am thinking of running another set of batteries in parallel for additional amperage, however I don’t think amperage consumption is the issue.

As of now, I’m using the midnight solar classic 200 for battery charge control.

See the attached pictures of the setup. I would greatly appreciate your recommendations.

Attached Images
jpeg 73535DAC-B8D2-402D-925F-68647FCDE75E.jpeg (2.02 MB, 21 views)
jpeg BE15C6D0-E0DE-4228-BFE4-EAFF88761DE2.jpeg (2.10 MB, 23 views)
jpeg 567415C3-F841-43EA-A06B-4436E4D3B619.jpeg (1.87 MB, 23 views)
jpeg 89C291DA-6157-4B08-B4E1-13C9C0CFF5C6.jpeg (3.36 MB, 23 views)
jpeg C0CA3DB6-6ED4-4519-B732-0A30C3238C60.jpeg (1.18 MB, 20 views)

stmbtwle

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Reply with quote  #2 
My thoughts are that you need a bigger battery bank, and that might require more solar panels to keep it charged.

What are you trying to do with this pump and how many hours a day do you expect it to run?

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
TopTierLandscape

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Posts: 5
Reply with quote  #3 
I am trying to irrigate a tree nursery for 3-5 hours every other day. The pump is connected to a 5000gal water reservoir which gravit feeds down to the mainline. The pump kicks in as the float in the tank triggers due to a decrease in water. It is not running at 100 percent for those 3-5 hours. When you review the pump label included in the pictures it draws about 22ampsncombined , should be more than sufficient for this system to handle given a 224amp battery cell I think. The mathematical aspect of it at least pencils.

On Monday I’m going to add one more panel, and create 2 strings of 900watts - which should provide 1700-1800 watts of energy coming from the panels.

According to my calculations this should work, given the system is only being utilized every other day. This is what is puzzling , as the inverter keeps on resetting due to low voltage.
stmbtwle

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Reply with quote  #4 
I think it's 11 amps, not 22. Still that's well over 2kw. Your batteries store a bit over 4 kwh at 80% DOD. IN THEORY, you should get nearly 2 hrs run time on a FULL charge.

My first guess is that your batteries aren't getting fully charged, and that points to solar. Also, what size wire are you using and how long a run from the batteries to the inverter?

Has this system ever worked?

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
TopTierLandscape

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Posts: 5
Reply with quote  #5 
I am using 4 gauge at the parallel connection coming from positive and negative from thbatteries to the inverter. 6 gauge between the batteries in series. Batteries to the inverter is 5-6 feet.
The system is a brand new system and has never been fully ran. In troubleshooting mode.
stmbtwle

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Reply with quote  #6 
It looked like about 4 ga in the picture. It's probably adequate but larger would be better. 
http://assets.bluesea.com/files/resources/newsletter/images/DC_wire_selection_chartlg.jpg

I'm stumped, sorry. I'm still inclined to think it's a charging issue, but if that were the case it should have worked the first time and failed later. Are all the batteries reading the same?


Maybe someone else has an idea.


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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
TopTierLandscape

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Reply with quote  #7 
Stmbtwle- I think I may have resolved this by reviewing the shots below. The total wattage consumed is greater than the total wattage available in the batteries, at any greater load than 50% of use. The batteries bank 5,424 watts combined (224x6)x4). The total load coming from the pump is 11amps x 230v = 2500 watts. Let’s call it 2800watts for the sake of running the pump and irrigation controller.

So 2800 per hour multiplied by 3 hours. Thats 8400watts through the course of 3 hours. The system is generating anywhere between 1700-1800 watts at peak optimal. Thus I am under the impression that I can only run the pump for about 2hours, like you said, and utilizing active wattage coming from the panels to counter the draw, in attempts of maintaining the batteries below the 50% discharge threshold.

My conclusion would be to add 3 more 300w panels, for 2700w and possibly add another 4 - 224/6 batteries to provide a bank of 10,700 watts to pull from.

My questions would be as follows:
If I run an additional bank of 4 batteries, running them in series and then paralleling the tail ends. Theoretically, 448 amps. And then I couple that with the first bank, also wired in the same format, at 448 amp Would that create a 896 amp hour bank at 24V?

What size shunt is recommended at that point? Is it determined by the total amps in the battery bank-896amps, thus a 1000amp/50v shunt?
TopTierLandscape

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Reply with quote  #8 
Oops I forgot to include th screen shots

Attached Images
png AEFBF031-D0E0-4C81-B141-61D5477E4493.png (444.15 KB, 14 views)
png 899A5D7F-C025-4CE8-8022-541A835D6A88.png (463.40 KB, 13 views)

stmbtwle

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Reply with quote  #9 
Yep, it always helps to do the math.

In series you add volts, not amps. So your 4 batteries produce 224 amp hours x 24v = 5376 watt hours. Add another string and you get 10752 watt hours. AGM batteries are supposed to be good to 80% Depth of Discharge. That gives you 8601 watt hours. You will just squeak in.
At the more common 50% DOD, you won't.

Another issue you're going to have to address is the solar panels. Solar panels RARELY give you rated output. Of my two systems, I seldom get much over 60%. Then there's the sun: the energy you receive is not constant, it's probably more like a sine curve (when it's NOT cloudy). My 6000w array almost never produces more than 1000kwh/month (in sunny Florida).

Try this site: https://pvwatts.nrel.gov/pvwatts.php
Plug in your numbers and it will give you an estimate of how much energy to expect per month.

Note: If you can put your pump on a timer so it ONLY runs in the middle of the day, you'll reduce the load on the batteries. Considering the cost of batteries, etc, you might look into a DC pump running directly off the panels. Do the math, it may not make any sense.


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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Rick H Parker

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Reply with quote  #10 

Amp Hour Capacity = 224 a/h @ 20 hr rate:  (11.2A discharge current.) 
With a 230V 11.7A load, the battery current will be ~117.00 Amps, More ten times the 20 hr rate.
The effective battery capacity will be way less then 224a/h and they will discharge fast.

True Battery Capacity does not change as the current go up. However the energy transfer efficiency does go down as the current goes up due to the bulk resistance of the battery. This will cause the effective capacity to be less then the true capacity ( Effective = True - Waste).

In other words, the higher the current, the higher percentage of electrical energy that gets converted to heat. That is why batteries get hotter the harder they are worked.

2800W * 3 h = 8400 wh
(24V*11.2A) * 20h = 5375 wh.

Your batteries don't even have enough capacity to cover 1 hour of run time at the 20 hour (11.2A), let alone at a discharge rate of 117A. 




Bigger battery bank needed.

(3h/0.25h) * 224AH =2688AH.  Then multiply by 2, for a reasonable battery lifespan .... ~ 5000-6000Ah @ 24V.


Conservation of energy tends to have a better Return On Investment (ROI) then producing more energy.  Investing in more efficient pumps may very well be a smart move.


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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
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