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Diallodjeri

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Posts: 7
Reply with quote  #1 
Hello folks,

I have a few questions about my system design.
I want to set up a system in region where there is an abundant sunlight throughout the year, precisely in west Africa. I might just not have enough storage to harness all that beautiful sunlight in order to power all my appliances at night, may be just enough storage to power the essential appliances at night.

I’m planning on buying 21 panels, Trina 265 Watts, that should give me around 5kw in shining day.
I want to set it up in way so I can power all my appliances during the day when there is plenty of sunlight to crank all the panels and also to fully charge my battery, Simpliphi PHI 3.4kWh (Lithium Ferro Phosphate). I want to know how can I set up my system so the appliances will only draw power from my panels and not from the battery during the day when the sun is shining, and this way I will draw power from the battery for my appliances that need to be on at night. I want to make sure this setup doesn’t impact negatively my battery life at all.

The dealer told me that I will be needed two charge controllers if I get 21 panels or one charge controller if I get 18 panels, and in that case the charge controller will be running at full capacity all time which is not a wise thing to do.

The dealer suggested an Outback 80 Amp 12/24/48/60 Volt Flexmax 80 MPPT Charge Controller and Outback Radian 3500 Watt 48 VDC Inverter / Charger .
The dealer said that I can connect my 21 panels in string of 3 panels with 2 charge controllers or 18 panels in string of 3 with 1 charge controller.

I would like to know how can I accomplish this goal.


Rick H Parker

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Reply with quote  #2 
I might just not have enough storage to harness all that beautiful sunlight in order to power all my appliances at night, may be just enough storage to power the essential appliances at night.

To predetermine the required storage, one need a consumption profile. How good the calculations are depend on how detailed the consumption profile is. You have anything to profile your consumption? Electric bills from the past two years?

I want to know how can I set up my system so the appliances will only draw power from my panels and not from the battery during the day when the sun is shining.

That will happen automatically, so put the worry out of mind.

The dealer told me that I will be needed two charge controllers

At 48V you would need a 100A charge controller to transfer at the rate of 5kW. 80A is not enough, 2*80A = 160A more then enough.

I want to make sure this setup doesn’t impact negatively my battery life at all.

There is only way to do, no negative impact at all, it is .. do not use the batteries at all. 
However the less the depth of discharge the less the negative impact. In other words the bigger the battery bank the longer it will last.

I get 18 panels, and in that case the charge controller will be running at full capacity all time which is not a wise thing to do.

It would be like lead footing a car all the time, it will do it but it will not last as long. Like the batteries, some extra beef will result in a longer lifespan.

 





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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
Diallodjeri

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Posts: 7
Reply with quote  #3 
I appreciate the imput.
Diallodjeri

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Posts: 7
Reply with quote  #4 
I don't have a hard number of my consumption yet, but I think is going to be 2 mini split AC, where one is 1350watts and the other is 580watt plus one refrigerator and one freezer. These are the appliances that will be running of the system. It looks like my battery may not be big enough for the project.

As long as I have a good charge controller, do I still have to worry about my battery being to small for the amount of energy my panels might produce. My understanding was that the charge controller will protect your battery from overcharging.
Rick H Parker

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Reply with quote  #5 
but I think is going to be 2 mini split AC, where one is 1350watts and the other is 580watt plus one refrigerator and one freezer.

Watts is power, the rate of transfer or conversion ... one could say power is the rate of consumption but not the quantity consumed.
David ate two apples in four minutes, Bob is a power eater, he ate two apples in two minutes. Both David and Bob consumed two apples but Bob the power eater did it faster.
David's power is 0.5 apples per minute. Bob's power is 1 apple per minute.

Batteries store energy not power.


To get the energy consumption, multiply the rate by the time in hours. For example: 1350 watts, 5 hours run time per day. 1350W * 5 hours = 6750 watt-hours = 6.750 Kilowatt-hours of energy consumption per day.  From there you want to get a profile of the consumption broken down to say 15 minute blocks. Your not going to get it perfect but the closer you get to true, the better the battery sizing estimates will be.



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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
Diallodjeri

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Posts: 7
Reply with quote  #6 
I really appreciate the help.
Diallodjeri

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Posts: 7
Reply with quote  #7 

Hi folks,

I'm really glad I can come to you guys with my solar energy questions. 

I want to learn as much as possible before I can start spending my money with confidence.

 

My daily consumption should be around 3.5 kWh and the night consumption should be around 1.5 kWh to 2 kWh, but I'm buying enough panels that can generate at least 5 kWh which should be enough to charge my battery and satisfy my load at the same time during a day.

 

I want  to know if I should still be concerned about having a too small battery for too big panels as long as I have a good charge controller seating between my panels and the battery.

If I understand the design, the charge controller should be protecting my battery from over charging as well as from over discharging. I can see how the over charging mechanism would work because the charge controller is seating between the panels and the battery. I just don't understand how the mechanism against over discharging would work though.

 

I was looking to buy (2) SimpliPhi 3.4 kw,  24v battery which would give me a combine storage of 6.8 kw for almost $7000, but I have seen some used forklift battery online with similar capacity for half of this price. I don't know much about a used forklift battery other than it's not sexy, it's bulky and heavy, but I'm willing to sacrifice the sexiness for efficiency. Does anyone knows about a forklift's lithium ion battery. Is that battery a good investment?

 Whatever battery I'm going to go to buy has to be a lithium ion battery because of its safe technology.

 

I just want  a system with a good critical components such as panels, charge controller, inverter and battery;  I don't need all those belts and whistles like communication hub, remote control feature, or any other extra fancy feature, but I do really want a good reliability plus a basic monitoring of the system  to see if everything is working like they supposed to. In order to accomplish that, what sort of basic monitoring device do I need?.

Rick H Parker

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Reply with quote  #8 

My daily consumption should be around 3.5 kWh and the night consumption should be around 1.5 kWh to 2 kWh, but I'm buying enough panels that can generate at least 5 kWh which should be enough to charge my battery and satisfy my load at the same time during a day.

It would help if you show how you came up with them numbers. 




I was looking to buy (2) SimpliPhi 3.4 kw,  24v battery which would give me a combine storage of 6.8 kw for almost 
$7000, but I have seen some used forklift battery online with similar capacity for half of this price.

The SimpliPhi 3.4 kw are nice batteries. To compare them with the forklift batteries, I would need to look at both datasheets. I cannot do that if I don't know what forklift batteries or cannot find the second datasheet.

When comparing two batteries you need to pay attention to the discharge rate also. The 3.4kWh @ C/2 on the  SimpliPhi 3.4 kw datasheet means when discharged in two hours time. Many use a slower discharge rate like C/20 so hey can advertise higher capacity. The capacity @ C/20 is always higher then the capacity @ C/2.  Some datasheets will callout C20 when they mean C/20.

With lithium ion the difference between C/2 and C/20 is not as great as the difference between C/2 and C/20 of lead Acid. Also the lifespan of lithium ion is not effected by depth of discharge like Lead acid is, the statement I made in #2 about lifespan can be ignored with lithium ion. However having extra capacity to carry you through stormy weather is a good idea. Not all days are going to be productive.


The Max current Output Capacity of the SimpliPhi 3.4 is 60 Amps. At the Nominal DC voltage of 25.6 that is 1.536 Kw, two of them would be 3.072 Kw. If your peak power is less then 3.000 Kw your be OK. If your peak power is greater then 3.000 Kw, your need more then two SimpliPhi 3.4 to meet peak demand when operating on battery power alone.

I just don't understand how the mechanism against over discharging would work though.

Some monitor the battery voltage then determine the depth of discharge based on the voltage. This is the least accurate method.
Most good charge controllers use the accounting method. They keep track of how much energy is going in and out of the bank, like balancing a check book. This method is more accurate.



I just want  a system with a good critical components such as panels, charge controller, inverter and battery;

What equipment are you considering?
Example:

  1. TrinaSolar TSM-265PD.08?
  2. SimpliPhi 3.4 kwh 24V, Forklift batteries XXX
  3. Outback 80 Amp 12/24/48/60 Volt Flexmax 80 MPPT Charge Controller and Outback Radian 3500 Watt 48 VDC Inverter / Charger .


It helps if you give us your location, West Africa is rather vague. Africa has a rather long coast line.
We suggest you put your location in your signature line, like you see directly below this line.


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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
Diallodjeri

Registered:
Posts: 7
Reply with quote  #9 
The system is going to be set up in Mali, West Africa. Here is the breakdown of my consumption: 2 mini split AC where one 1350 watts and the other is 580 watts, one LG french door refrigerator, one  commercial grade freezer and one electric stove; the rest is just house lights and other small household items like flat screen tv, dvd player etc...

AS far as equipment I'm considering are: 1.TrinaSolar TSM-265PD.08,
                                                            2.Outback Power Radian GS3548E > 3500 Watt 48V Inverter/Charger
                                                            3.SimpliPhi 3.4 kwh 24V  
These are the equipment I'm considering right now, but I need help from you guys to determine if I'm making the right choice.
stmbtwle

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Posts: 2,782
Reply with quote  #10 
I think you might want a bigger inverter. If you're cooking and the AC cycles on...
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