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sran

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Posts: 9
Reply with quote  #1 
Hi forumers,
I cut it short straight to the point. I have a profitable business in East Java, Indonesia. So, I want to give back to the community by tackling some of the problem they're having which is electricity and the cost that comes with it. Most rural areas have power failure 2-4 times every month with 1-3 days recovery each time. According to their bills, their consumption on average 500Wh daily. Indonesia use 230VAC 50hz.

I have a bunch of good read regarding solar system but everytime I search for products, I have trouble getting the right one. I'm getting more confused when the information contradict each other with my lack of knowledge.

I'm planning to use 18650 used batteries as storage and an off grid system. Basically I want to free them from the grid for good.

What I figured;
18650 battery x 120 cells with 6s20p configuration = 888W.
500Wh x 1.5 fudge factor = 750Wh.

How many watt per panel, how many panel? Brand?
What brand/model of decent MPPT?
What brand/model of decent inverter?

*I prefer straightforward brand, model or link to each item. I'm a bit fool to search for it, will get confuse when I read the spec.

**I don't want to supply stuff that break in a year or two but I don't want to pay premium price too since if I can get mediocre balance system and price, I can provide more house.

Thank you very much.

Rick H Parker

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Reply with quote  #2 

18650 battery x 120 cells with 6s20p configuration = 888W.
I'm planning to use 18650 used batteries as storage and an off grid system.

If they are used, the performance is not going to be what is on the spec sheet. Also your be mixing cells with uneven capacities, that throws a monkey wrench in predicting performance. Capacity declines as the cells are used. How much depends on how hard they where worked and for how long. Why where these cells taken out of service and what is their work history .... ? 

500Wh x 1.5 fudge factor = 750Wh.

No reserve capacity to carryover the days sunlight is not good. To go off grid, a larger battery bank will be needed. If the sun does not shine for three days one would need 1500Wh of storage to carryover, 2250Wh with the fudge factor.

How many watt per panel, how many panel? Brand?
What brand/model of decent MPPT?
What brand/model of decent inverter?

Not enough information yet. A profile of energy and power consumption is needed first. 

I don't want to supply stuff that break in a year or two but I don't want to pay premium price too since if I can get mediocre balance system and price, I can provide more house.

Go with Pulse Wave Modulation (PWM) instead of MPPT.  PWM cost a lot less then MPPT and is such mature technology any company worth its salt can build good PWM charge controllers.

The choice between PWM and MPPT has to do with economics. PWM is optimized to get the best battery lifespan at the expense of Solar panel production. MPPT is optimized to get the most production out of the solar panels at the expense of the battery lifespan. When the cost of solar panels was higher then it is today, MPPT produced a better balance sheet. With today's solar panel prices, PWM produces a better balance sheet. The batteries are becoming the most expensive component in the system, in the past it was the Solar panel production.


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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
stmbtwle

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Reply with quote  #3 
Those batteries seem a strange choice to me, too. Are they free?

In your area, 500w of solar panels should give you at least 41kwh per month, or about 1300wh per day average. 2, 250w, 24v panels in parallel would be easy to install and relatively inexpensive. If shipping costs are a problem you might be better with say 4 x 125w panels or 6 x 100w.

I don't think an MPPT controller would be cost effective so I would choose a 24v, 30a PWM controller.

Inverters have to be sized to the peak load, but I'm guessing lights and electronics, so 500w, 24vdc/230vac should be enough, if in doubt go 1000w. Full sine wave is better but MSW generally works quite well, even with electronics, and is less expensive.

Sorry I can't provide links as I don't know what is available in your area, nor shipping costs.  

And that brings us back to batteries.

http://pvwatts.nrel.gov/pvwatts.php

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

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Posts: 9
Reply with quote  #4 
Those cells are easy to get on my part. I can get new cells and cost cheaper than deep cycle battery here. All the cells I can get have minimum of 2400mah and maximum 3000mah. I separate those in different setup. I can do bigger storage if that what it takes but East Java have very good sunlight. 

If I use PWM, it means I have to increase PV watt, right?


sran

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Posts: 9
Reply with quote  #5 
The battery ain't free but it's really cheap. It's not no-brand-unreliable battery. So far I can get my hands on Panasonic & LG. I learnt that tesla use Panasonic 18650 too? Either way, I'm prepared to replace the batteries if it goes down after a year or so. Well, they can't complained on free stuff.

For the parts such as charge controller, inverter and PV, the important thing is I get the product cost. Dont worry about shipping.

As for now, 1 part solved. 24v 30a PWM controller


Rick H Parker

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Reply with quote  #6 
Sorry I can't provide links as I don't know what is available in your area, nor shipping costs.

Indonesia has eBay, he can get the same gear, deals and prices we do.


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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
stmbtwle

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Reply with quote  #7 
Fair enough, but the products don't always seem to be the same.

Would you recommend a 12v or 24v system? I'm leaning toward 24v but 12v would work, depending on panel and battery selection.

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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  #8 
Fair enough, but the products don't always seem to be the same.

If we find him the right gear. Good chance he could use his business account to buy in bulk direct from the Chinese suppliers and pay wholesale.

Would you recommend a 12v or 24v system? I'm leaning toward 24v but 12v would work, depending on panel and battery selection.

TBD, 18650 are 3.7v Li-ion cells. He thinking 6 cells per string, 6 * 3.7 = 22.2V.


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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
stmbtwle

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Reply with quote  #9 
My thought too.  The bigger 24v panels are cheaper for what you get but the freight is a killer.  If he can buy them by the pallet it would be less expensive.  

Most "kits" in that size are 12v it seems, and those batteries could be configured for "12v" if desired.  4 x 3.7 is 14.8v which should work for an inverter.  I think 11.1v might be too low.  22.2v might be OK for a "24v" inverter. 

The controller would have to be programmable.

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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 
but the freight is a killer

He is a lot closer to China then we are. Freight should not be the killer it is for us.  Customs might be a different story.

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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
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