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Pazuri Powerwall
#1
Hi all,

I have been drinking the 18650 kool aide and I have decided to take the plunge. I am a huge all things renewable fan from solar harvesting, rain water harvesting, grey water recycling, etc.

After watching very many helpful videos from HBPowerwall, Will Prowse, Dave Poze, Lithium Solar, DIY Tech and Repairs, Jehu and others (many thanks to you all "solar gods"), I felt I can go for something substantial from the word go.

The powerwall is to power a poultry project, that includes 130W freezer, 5 x 100W heating lamps, security lights (max 100W) and other miscellenous appliances

My first set up:
  • Target: 4.84 kWhVoltage: 24VConfig: 7S100P

Components:
  • 700 18650 cells from used laptop batteries
  • 1 x Liitokala Li-500
  • 38 x TP4056 charging modules (30 in the mail)
  • 4 Opus BT-3100 for charging (being ordered)
  • 4000W Reliable Inverter
  • BMS from china
  • EPever MPPT Tracer120AN charge controller
I am currently collecting and testing cells with ~400 cells currently in the kitchen but the rest of the components have already been delivered. During cell testing, I measure and record the original cell voltage, charge them fully and record that voltage too, let them sit for 3-4 weeks then record their voltages too. The plan is then to pop them into the Liitokala or OPus for testing of actual capacity as well as IR. All this data is logged in a google spreadsheet

One major question is how to monitor the whole setup remotely. The farm is 150KM away and I would like to log each and every parameter online if possible. I am ok with programming with arduinos but I wont mind using off the shelf solutions. Any leads will be very welcomed.

I am also battling with selecting/sizing the best solar panels for such kind of a setup. I have a lead of a 200W, 22.2V, 7.54A panel, but I don't know if this will be enough. Any leads and pointers will also be very helpful.



The link to the google spreadsheet --> https://docs.google.com/spreadsheets/d/1...sp=sharing
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#2
Nice setup so far. Good beginnings.

I first read "power a poultry project" as was initially thinking "small". Then later I see you refer to a farm. Must be "real" birds, eh? Tongue

For remote monitoring you'd need internet on the farm. Then set up influxdb and grafana on a server that you can access remotely. Rpi is a good way to get a quick jump start in that area. Or if you have an older computer/laptop that's collecting dust, you can repurpose it.


Question: How come you went with 24V setup? At least you aren't going with 12V Tongue
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#3
(06-26-2020, 03:05 AM)Korishan Wrote: Nice setup so far.  Good beginnings.

I first read "power a poultry project" as was initially thinking "small". Then later I see you refer to a farm.  Must be "real" birds, eh?  Tongue

For remote monitoring you'd need internet on the farm. Then set up influxdb and grafana on a server that you can access remotely. Rpi is a good way to get a quick jump start in that area. Or if you have an older computer/laptop that's collecting dust, you can repurpose it.


Question: How come you went with 24V setup?  At least you aren't going with 12V Tongue

Thanks

Yes, real birds, capacity of 2000 birds, but since Covid happened, we are down to 700.

I currently have internet on the farm, no problem there. I have a server that I can send data to and access remotely, check that too. I have a couple Rpis which I can use, check that too. I think my main question is how to get the data from the charge controller and inverter?

As for 24V, I opined that 12V is small and 48V is an overkill. No hard data was used to arrive at that opinion  Sad Rolleyes
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#4
(06-26-2020, 03:35 AM)Solloh Wrote: Yes, real birds, capacity of 2000 birds, but since Covid happened, we are down to 700.

Ouch, 2000 to 700. That sux. Hopefully things will pick back up and get a full flock again soon.

(06-26-2020, 03:35 AM)Solloh Wrote: I think my main question is how to get the data from the charge controller and inverter?

With that inverter, you might not get much from it itself. You need to use something else to do the monitoring.

On the AC side of things, you could use OpenPowerMonitor, which is an open source power monitoring solution. I'm using the custom built version, putting the components together myself. There are other solutions as well.
For the DC side, you'll want to get some kind of Shunt sensor

Both of the results can be fed into the Rpi and uploaded.

(06-26-2020, 03:35 AM)Solloh Wrote: As for 24V, I opined that 12V is small and 48V is an overkill. No hard data was used to arrive at that opinion  Sad Rolleyes

12V for small, and 48 for large. Hrmmm, yeah, it's not like that. At least not directly.

Let's say you have a 3000W load on that inverter. 3000W / 120V = 25A. Seems fine on the AC side. Using 10AWG can handle that current w/o a problem. But what about the DC side? 3000W / 24V = 125A. Now to handle 125A, you're going to need a muuuuuch larger cable. You'd need 1/0 at least, and better to go 2/0. Not only are they harder to work with, but also more expensive.
Now lets go to a 48V comparison: 3000W / 48V = 62.5A. Now you'd only need 4AWG, which is easy to work with, and quite common in welders wire format to make it even better.

The higher the voltage, the smaller the wire for any given amperage. There's a few sections in the FAQ that discuss these things Wink

Another thing about using LiIon cells and "24V" setup. Your operating voltage range for LiIon is 3.2V - 4.2V absolute max. With a 7s system, that'd give you a range of 22.4V - 29.4V. In comparison a lead acid would be 21V - 29V (assuming 10.5 - 14.5V per battery). This seems to fit, but you'll kill your LiIon battery bank as you're basically running them cells at peak capacity each cycle. Considering you're using recycled cells that 1) you don't know their life cycles used and 2) are going the recycled route, you want to make these last as long as possible. Soooo, that would mean you'd want to pull their effective voltage range in a bit. So it'd be recommended for 3.5 - 4.0V range, or for 7s: 24.5 - 28V. With this range, we are now below what lead acid could do. You could go with 8s (28 - 32V), but that goes way over.
In either case, if the charger and inverter can operate just fine in these ranges, that's fine. But it's harder to get both devices to operate exactly in those ranges. Not saying it can't be done, just takes more effort.

Now, I'm not saying there's nothing *wrong* with using 24V. You can use it if you want. That's totally up to you. Smile
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Certified 18650 Cell Reclamation Technician

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#5
(06-26-2020, 06:35 AM)Korishan Wrote: Ouch, 2000 to 700. That sux.  Hopefully things will pick back up and get a full flock again soon.
Thanks. Things will be better


(06-26-2020, 06:35 AM)Korishan Wrote: On the AC side of things, you could use OpenPowerMonitor, which is an open source power monitoring solution. I'm using the custom built version, putting the components together myself. There are other solutions as well.
For the DC side, you'll want to get some kind of Shunt sensor

Both of the results can be fed into the Rpi and uploaded.
Thanks. This is really helpful

(06-26-2020, 06:35 AM)Korishan Wrote: Let's say you have a 3000W load on that inverter. 3000W / 120V = 25A.  Seems fine on the AC side. Using 10AWG can handle that current w/o a problem. But what about the DC side?  3000W / 24V = 125A. Now to handle 125A, you're going to need a muuuuuch larger cable. You'd need 1/0 at least, and better to go 2/0. Not only are they harder to work with, but also more expensive.
Now lets go to a 48V comparison: 3000W / 48V = 62.5A.  Now you'd only need 4AWG, which is easy to work with, and quite common in welders wire format to make it even better.
I only looked at this from the AC side, hadn't considered the DC side. I will see a workaround for that, either limit the max wattage that can be drawn or buy the bigger cables and limit the distance from battery to inverter. I can also use it later in a smaller project that I will be building.

(06-26-2020, 06:35 AM)Korishan Wrote: Another thing about using LiIon cells and "24V" setup. Your operating voltage range for LiIon is 3.2V - 4.2V absolute max. With a 7s system, that'd give you a range of 22.4V - 29.4V. In comparison a lead acid would be 21V - 29V (assuming 10.5 - 14.5V per battery). This seems to fit, but you'll kill your LiIon battery bank as you're basically running them cells at peak capacity each cycle. Considering you're using recycled cells that 1) you don't know their life cycles used and 2) are going the recycled route, you want to make these last as long as possible.  Soooo, that would mean you'd want to pull their effective voltage range in a bit. So it'd be recommended for 3.5 - 4.0V range, or for 7s: 24.5 - 28V. With this range, we are now below what lead acid could do. You could go with 8s (28 - 32V), but that goes way over.
Thanks for this. I had considered this and I am not so much concerned on operating below the lead acid capacity. In this part of the world I have seen that I can get cells at a song, only that the processing takes a lot of time and effort. It seems I will definitely upgrade to 48V at a later stage.

(06-26-2020, 06:35 AM)Korishan Wrote: In either case, if the charger and inverter can operate just fine in these ranges, that's fine. But it's harder to get both devices to operate exactly in those ranges. Not saying it can't be done, just takes more effort.
In the meantime I will try and get these perfectly set.

Thanks alot for the advise and great tips.
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#6
Best option would have been to buy an 5048 pip. 48v 5kw inverter with built in solar charger and inverter. You get all the data easily out with for instance solar- sis on a raspberry pi and you dont have to fiddle around.

Then add a proper bms that you can do logging from that is smart instead of the one you choosed.

The gear you have picked up are cheap for a reason and the only one you get data from are the charger.
Combining la and lithium is just not worth it. You either degrade the la or the lithium. You gain alot running them separated. Lithium arent made to be fully charged nor to have float/bulk charge. La are always ment to be fully charged and bulk/floated.

You have done the most common mistake here if you ask me Smile You have gone out buying stuff before you laid out all the parameters you wanted to solve.

Note: You should only test with 1 brand. You get different results otherwise that can result in issues.
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#7
(06-26-2020, 08:53 AM)daromer Wrote: Best option would have been to buy an 5048 pip. 48v 5kw inverter with built in solar charger and inverter. You get all the data easily out with for instance solar- sis on a raspberry pi and you dont have to fiddle around.

Then add a proper bms that you can do logging from that is smart instead of the one you choosed. 

The gear you have picked up are cheap for a reason and the only one you get data from are the charger.
Combining la and lithium is just not worth it. You either degrade the la or the lithium. You gain alot running them separated. Lithium arent made to be fully charged nor to have float/bulk charge. La are always ment to be fully charged and bulk/floated.

You have done the most common mistake here if you ask me Smile  You have gone out buying stuff before you laid out all the parameters you wanted to solve.

Note: You should only test with 1 brand. You get different results otherwise that can result in issues.

Thanks daromer for the input and insights. I appreciate you taking the time.

As you have correctly pointed out, the gear that I have picked is cheap and from China. In my neck of woods, we don't have the leisure of amazon and ebay and in case they are available shipment + customs costs an arm and a leg, hence its a no-no for me for now.

I love tinkering with stuff so buying one big thing that does all the work isn't that much fun! In addition I want to learn by doing, so some mistakes here and there aren't catastrophic. I also plan to build other bigger/smaller systems so the components that are oversize/undersize can be re-purposed later on.

Thanks for the La and lithium insights, I am only doing Lithium Ion, no lead acid for me. I will follow the advice of cycling them between 3.5 - 4.0V to get as much cycles from them. Later on I will upgrade to 48V and maybe then I can think of a bigger more expensive inverter.

Muchas gracias
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