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stmbtwle

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Reply with quote  #21 
So that boils down to $120-240 per set, plus whatever it costs to "assemble" them. Is there a plan for that yet?
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sran

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Reply with quote  #22 
Assemble is free as I'm using my worker free-time-at-work.
stmbtwle

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Reply with quote  #23 
That's good, and materials for the battery box shouldn't be much.

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Rick H Parker

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Reply with quote  #24 

Panasonic NCR18650B

I was hoping you could get the
technical specifications. The Datasheet does not tell some things that would be real helpful, like Depth of Discharge vs Cycle life, the effects of charging voltage stress on cycle life, Discharge rates vs capacity,... ect.  Without that information, the best I can do is workout out guesstimates base on Li-ion typicals.

One way Telsa and the other EV/Hybrid manufacturers get a long life out of li-ion cells, is to lower the charging voltage and raise the minimum depth of discharge. Theoretically these cells can last 40,000 cycles if you don't stress then out by charging then past 4.0V per cell or discharging them below 20 - 30%.  The trade off is the usable capacity is lower, that raises the required number of cells.

So that boils down to $120-240 per set, plus whatever it costs to "assemble" them. Is there a plan for that yet?

Willie is on to a good point. There will be some material overhead other then the cells. Heat kills these cells, that is why Telsa water cools them. Clearly water cooling is out of your financial budget and the systems energy budget but, mounting the cells in racks that allow air circulation between the cells for better heat dissipation might be cost effective in the long run.

I been working the model on 500Wh/day then I recalled Sran want to fudge it to 750Wh/day. 750Wh/day pushed the PV panels up to ~200W and the battery pack up to ~156 cells. If I lower the charging voltage and raise the minimum DoD for a longer lifetime the number of cells will go up.  The low voltage cut off of the inverter would naturally limit the DoD. I have yet to take a look at what the Dod would be at the typical low voltage cut out of a 24V inverter. We will also need to look at the over voltage cutout of the inverter to the charging voltage of the battery bank doe not turn off the inverter.


Sran - Can you quantify the peak power requirements so we can size the inverter?  We are going to need this to match the battery bank to the inverter. Also time of day the people use electric would be helpful, the closer the usage profile is to actual usage the better the model. 


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Rick H Parker
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stmbtwle

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Reply with quote  #25 
Probably hard to predict as everyone is different.  The size of the inverter does have an impact on the load on the batteries, so the load could be "restricted" by reducing the size of the inverter.  A 150w inverter would run a laptop, a few LED lights, a cell-phone charger, and a transistor radio for several hours. I don't know what else folks might try to use on a system that size.  Any kind of refrigeration is probably out.

However human beings are packrats, and the bigger the inverter the more "stuff" they will eventually plug into it, until they overload the system and kill the batteries.

I think some kind of charge meter might be a good idea.


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

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Reply with quote  #26 
However human beings are packrats, and the bigger the inverter the more "stuff" they will eventually plug into it, until they overload the system and kill the batteries.

Not every culture has the collective lack of ethics and constraint that us Americans have.


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Rick H Parker
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Rick H Parker

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Reply with quote  #27 
I'm thinking the way to approach this project is to start with a Hybrid inverter then design the battery bank around it.

For example: 800 - 1000W @230V, built in li-ion compatible charge controller, for $79.00 each or less with a minimum order of 50 units.  This example is modified sine wave but I am seeing some units that are pure sine wave. Units like this would simplify the whole project.

12v/24v, 110V/220V/230V/240V inverter dc to ac pure sine wave inverter li-ion battery charger.


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Rick H Parker
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sran

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Reply with quote  #28 
I was hoping you could get the technical specifications.

This one here looks like what you're looking for. https://actec.dk/media/wysiwyg/Actec/PDF/NCR-18650B.pdf


Can you quantify the peak power requirements so we can size the inverter?

I can't. I met a family living way below average, had a chat & all, looked at his electricity bill, that's how I found out their 500wh. They have a 2 doors fridge (not big, not too small), no-brand lcd tv. Say 1 bulb each room, maybe 8 bulbs total. They have no microwave, no electric kettle & stove & I'm pretty sure they don't have a blender because they prefer "traditional way".

He told me that the bill shouldn't be that high IF there's no power failure (i know it's really low for us but anyway). He said that when the power comes back, the surge blow their bulbs and he believe that power rushed in = electricity spike = more usage.
Honestly, IDK, I have no idea whether it's true or not but if they can be free from the grid, none of that matters. Change their bulb to the spiral type (the one that use less power) is not a big deal to lower their consumption.


I think some kind of charge meter might be a good idea.

What's this charge meter? Some kind of usage limitation? If it is, it's a good idea. Although I can teach them how to calculate their power consumption, I doubt they will add anymore stuff. That extra bill's money gonna head straight to groceries.


p/s: Since I can't find suitable inverter/charge controller for low usage before, I had this idea to put 2kW+ in 1 house and share the power with the neighbour. Alas, it's better to have 1 low system for 1 house.



stmbtwle

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Reply with quote  #29 
By a "charge meter" I meant something like a "gas gauge" so the user knows when the battery is getting low and adjust usage accordingly. Something like this https://www.ebay.com/itm/1S-2S-3S-4S-Lithium-Li-ion-18650-BMS-Battery-Capacity-Level-LED-Indicator-Meter/122376562254?hash=item1c7e36264e:m:mY9EKRC3n088k80qJYnCMhg

or this
https://www.ebay.com/itm/DC100V-10A-50A-100A-Voltmeter-Ammeter-LED-Dual-Digital-Volt-Amp-Meter-Gauge-Test/263121896994?hash=item3d43498622:m:m1fAJG7en2kGamz3njI3x8w

I would love to know the brand of that fridge! My medium-sized 2-door fridge uses about 1000wh/day by itself, it's the single biggest load.

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

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Reply with quote  #30 
I think the fridge if they have one is going to be the biggest load over time, and the starting load has to be taken into account. Compared to that the rest is minor.

"p/s: Since I can't find suitable inverter/charge controller for low usage before, I had this idea to put 2kW+ in 1 house and share the power with the neighbour. Alas, it's better to have 1 low system for 1 house."

Might work to build a pre-wired assembly with charge control and inverter, meters, etc at the shop, and install it as a unit.

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