New to solar, just bought 71 kWh of batteries for DIY some help please :)

[doox00]

I am going to be setting up solar in my new home. I plan to run off solar/batteries and will still be connected to the grid in case no sun and batteries are dead. I also have a whole house generator that can be incorporated into this as well. These batteries are the first thing I have bought so far. I found these batteries from DavidPoz youtube channel where he went over these modules and built a battery. I will link his video below and link the batteries for sale for reference.

My question(s) is I assume I need a BMS of some sort? I had originally planned on using a EG4 18K inverter since it seems like it will seamlessly connect grid power, generator, batteries and panels, which I want, not looking for something super complicated (other than maybe building these battery packs) but if others have suggestions of what else to look into I am all ears. I assume the bms I choose depends on the inverter I am using, is this correct? Does the EG4 18K have a bms built in or do I need to wire and install one for each 16c pack I will be building (5 packs total). Thanks all for any info!

Video:

Batteries I purchased (bought 2 of the 2 module crates):

New CATL Modules with 20x 3.2v 280ah Prismatic - 17.92kWh - $110-$120/cell

Down to our last pallet. These modules are new in the crate, never touched. 100% automotive grade, not reject grade B or A-. These are the batteries that were not rejected by automotive quality control. Each crate has 2 modules. The only crate that was open was the one we opened for the photos...

batteryhookup.com

 

[Rednecktek]

You'll need a BMS for every pack you build. The inverter doesn't talk to the cells directly, at best it communicates with the BMS.

He goes over it in his video about running the balance leads but kinda glasses over it unfortunately.

71Kwh of battery? Isn't that something like 8 16s packs? You'll need 8 BMS's for that.

 

[doox00]

You'll need a BMS for every pack you build. The inverter doesn't talk to the cells directly, at best it communicates with the BMS.

He goes over it in his video about running the balance leads but kinda glasses over it unfortunately.

71Kwh of battery? Isn't that something like 8 16s packs? You'll need 8 BMS's for that.

It will make 5 packs, each pack will be 14.3Kwh so I will need 5 BMS's total.

 

[400bird]

The BMS is never integrated into an inverter, you'll need to source and supply that.

Do yourself a favor and search here for Signature Solar reviews. If you are new to this, you'll likely need support. Signature Solar may leave you wanting in that area. And EG4 is the house brand for Signature Solar (owned by the same person), do some research on the company before purchase.

 

[MrM1]

I saw that video back several weeks ago. Looks like a lot of extra work to separate the cells. Wondering why you didn't just buy new loose cells?

 

[doox00]

I saw that video back several weeks ago. Looks like a lot of extra work to separate the cells. Wondering why you didn't buy just new loose cells?

I am new to all this and not sure where you would buy brand new grade A cels from. It seems like these were a good deal, be like 130-140 dollars per Kwh once fully built.

It does not seem like too much work, I will just cut the battery bar to disconnect the 4 cels and leave them in the tray banded as they are. I will have 4 extra cels in each of the 4 trays so can make a 5th with the "extra" 16 cels.

 

[a619]

@doox00, there are a ton of nuances in terms of cable sizing/ length etc when it comes to paralleling battery packs, so be sure to read up on that. Apart from that, I would suggest you follow Ravi's method of re-configuring these which seems fairly straightforward.
For future reference, you can buy brand new "A" grade EVE/ CATL cells from various suppliers either in US or through China. Some of the prominent ones are 18650batterystore/ currentconencted/ Docanpower/ Seplos etc.

 

[doox00]

@doox00, there are a ton of nuances in terms of cable sizing/ length etc when it comes to paralleling battery packs, so be sure to read up on that. Apart from that, I would suggest you follow Ravi's method of re-configuring these which seems fairly straightforward.
For future reference, you can buy brand new "A" grade EVE/ CATL cells from various suppliers either in US or through China. Some of the prominent ones are 18650batterystore/ currentconencted/ Docanpower/ Seplos etc.

Thank you for the info. Looks like a decent deal with these modules I bought after checking the stores you mentioned, they are ~135 each for new individual 280ah cels (not sure if shipping is extra, which would make them cost a bit more), I paid 9150 shipped for the 80 that are in packs and are already in a tray with battery bars etc.

Have a link to Ravi's method of reconfiguring these modules?

 

[MrM1]

I am new to all this

Just be VERY CAREFUL cutting and separating the cells. A task Not for the "faint if heart". Nicking or damaging a cell could / will lead to a fire. Damage might take a long time to reveal itself. Be gentle.

The cases are very thin.

 

[DIYrich]

Have you figure out how to move a pack of 16 cells? The 4 you cut off are not that bad to move. the 16 are really heavy.
Have you figured out where to put them?

Something to consider: If you get a Sol-Ark 16k, there is a benefit to making 17 cell packs. You can get closer to the 15k output at 54.4v. The 15k maxes out at 275 amps from the battery, but you can run a 17 cell pack at 54.4 volts (vs 52.0 for 16 cell pack).

 

[Shawn Hayes]

I am going to be setting up solar in my new home. I plan to run off solar/batteries and will still be connected to the grid in case no sun and batteries are dead. I also have a whole house generator that can be incorporated into this as well. These batteries are the first thing I have bought so far. I found these batteries from DavidPoz youtube channel where he went over these modules and built a battery. I will link his video below and link the batteries for sale for reference.

My question(s) is I assume I need a BMS of some sort? I had originally planned on using a EG4 18K inverter since it seems like it will seamlessly connect grid power, generator, batteries and panels, which I want, not looking for something super complicated (other than maybe building these battery packs) but if others have suggestions of what else to look into I am all ears. I assume the bms I choose depends on the inverter I am using, is this correct? Does the EG4 18K have a bms built in or do I need to wire and install one for each 16c pack I will be building (5 packs total).

Too late if you’ve already purchased the batteries. I would HIGHLY recommend reading, researching what you’re about to get into BEFORE buying anything!!
I was brand new here 3 hrs ago, didn’t know a thing about any of this!! Take it from me, read, research multiple ways of doing anything before buying!! I would recommend researching the eg4 or signature Solar thoroughly here before buying anything!!
As for batteries, to me, buying individual (280 or 304ah) cells is much easier to assemble, disassemble and handle.
Inverter
Batteries
Battery rack or storage setup
BMS
Battery Cables
Bus bars for paralleling multiple strings of batteries
Class T fuses
DC breakers
Compress or not to compress cells
Quality comes at some cost!!!

 

[Brucey]

Have you figure out how to move a pack of 16 cells? The 4 you cut off are not that bad to move. the 16 are really heavy.
Have you figured out where to put them?

Something to consider: If you get a Sol-Ark 16k, there is a benefit to making 17 cell packs. You can get closer to the 15k output at 54.4v. The 15k maxes out at 275 amps from the battery, but you can run a 17 cell pack at 54.4 volts (vs 52.0 for 16 cell pack).

Maybe use a Schneider inverter/charger looks like it can handle up to 68V in and charges at upto 64V. So might be able to use the full 20 cell packs?

 

[Brucey]

Sorry that the non expandable one I'm assuming the bigger xw units that can be paralleled have similar specs

 

[rhino]

As others have mentioned I would also question whether or not it is a good idea for you to be starting out with those batteries. The "grade" of the battery is of little concern for 99% of the people on here because "grade B" works great in a solar system.

 

[OffGridForGood]

"I am just starting out" - so I bought $9,000 of EV cells, then asked if I need a BMS...
ok, so you are new to solar, and just starting out. maybe a bit impulsive, but well financed, and not scared of a challenge. Perhaps you have some experience with electricity and just need to gain some knowledge about Inverters/DC/Solar/BMS. Clearly new to the forum(few postings only), and that is a good start. Welcome to the DIY-Solar Forum, there are a lot of people here happy to help.
First up,
There are a lot of similar set-ups to what you are planning posted on the forum - I suggest taking the time to do searches and read over a number of these that parallel your plans.
Starting with the batteries, instead of the loads you will need to power is backwards, although I do understand the impulse to get the cells when you see what appears like a good deal, endorsed online and all that. I don't mean those cells are a bad deal either, but no-one here would have recommended them to someone just starting out.
Second,
A system should be designed for it's eventual full capacity, even if you start smaller and add to it. What are your loads? what will be the peak in-rush start up current needed for motors, A/C, Well pump, Heat pumps? - see the resources section find the speadsheet that FilterGuy posted there. If your building new, perhaps your current loads (electrical bills) will give you some guide to the new loads.
Third,
Plug in your location to PVWatts and see what you can expect for Solar potential in your new area, shading snow, dust, pollen all reduce these numbers.
Forth,
Post your questions, ask for some input/advice there is a wealth of experience and knowledge at your fingertips - just for the asking.

 

[doox00]

Just be VERY CAREFUL cutting and separating the cells. A task Not for the "faint if heart". Nicking or damaging a cell could / will lead to a fire. Damage might take a long time to reveal itself. Be gentle.

The cases are very thin.

I am not taking the cells apart, I am just cutting the bar to remove 4 of the cels to leave a 16c pack.

 

[doox00]

Have you figure out how to move a pack of 16 cells? The 4 you cut off are not that bad to move. the 16 are really heavy.
Have you figured out where to put them?

Something to consider: If you get a Sol-Ark 16k, there is a benefit to making 17 cell packs. You can get closer to the 15k output at 54.4v. The 15k maxes out at 275 amps from the battery, but you can run a 17 cell pack at 54.4 volts (vs 52.0 for 16 cell pack).

They are about 300 pounds a pack, I have pallet jacks and a few people who can help put them into a rack once they are built. I bought 4 modules of 20 cells so that will be enough to make 5 16c packs. I considered the eg4 18k inverter but have not decided on that yet. I would like it to seamlessly connect to the panels, batteries, grid and generator.

 

[doox00]

Too late if you’ve already purchased the batteries. I would HIGHLY recommend reading, researching what you’re about to get into BEFORE buying anything!!
I was brand new here 3 hrs ago, didn’t know a thing about any of this!! Take it from me, read, research multiple ways of doing anything before buying!! I would recommend researching the eg4 or signature Solar thoroughly here before buying anything!!
As for batteries, to me, buying individual (280 or 304ah) cells is much easier to assemble, disassemble and handle.
Inverter
Batteries
Battery rack or storage setup
BMS
Battery Cables
Bus bars for paralleling multiple strings of batteries
Class T fuses
DC breakers
Compress or not to compress cells
Quality comes at some cost!!!


View attachment 167951View attachment 167952View attachment 167953View attachment 167954View attachment 167952

Yep, I am in the research phase now and I knew I wanted to diy the batteries, can get double or more the storage for the same cost as off the shelf batteries. I am a diy type person so I don't mind a challenge and I am not taking this pack apart, only cutting the battery bar to remove 4 of the cells to leave me a 16c pack. I bought 4 modules of 20 cells, allowing me to make 5 16c packs.

 

[doox00]

"I am just starting out" - so I bought $9,000 of EV cells, then asked if I need a BMS...
ok, so you are new to solar, and just starting out. maybe a bit impulsive, but well financed, and not scared of a challenge. Perhaps you have some experience with electricity and just need to gain some knowledge about Inverters/DC/Solar/BMS. Clearly new to the forum(few postings only), and that is a good start. Welcome to the DIY-Solar Forum, there are a lot of people here happy to help.
First up,
There are a lot of similar set-ups to what you are planning posted on the forum - I suggest taking the time to do searches and read over a number of these that parallel your plans.
Starting with the batteries, instead of the loads you will need to power is backwards, although I do understand the impulse to get the cells when you see what appears like a good deal, endorsed online and all that. I don't mean those cells are a bad deal either, but no-one here would have recommended them to someone just starting out.
Second,
A system should be designed for it's eventual full capacity, even if you start smaller and add to it. What are your loads? what will be the peak in-rush start up current needed for motors, A/C, Well pump, Heat pumps? - see the resources section find the speadsheet that FilterGuy posted there. If your building new, perhaps your current loads (electrical bills) will give you some guide to the new loads.
Third,
Plug in your location to PVWatts and see what you can expect for Solar potential in your new area, shading snow, dust, pollen all reduce these numbers.
Forth,
Post your questions, ask for some input/advice there is a wealth of experience and knowledge at your fingertips - just for the asking.

I said I assumed I need a BMS, my question is more of which kind and if the kind I need matters depending on which inverter I get. Yep I am new at this and I knew I was going to diy the batteries shortly after starting to read up on things as its half or less the cost of prebuilt ones and I am a diy kind of person. Also I am not separating the cells, just cutting the bar to remove 4 of the cells from the 20 cell packs. The extra 4 will physically remain and I will connect those 4 extra from each of the 4 modules to make a 5th 16c pack.

My loads are a well pump, shop with some 15-20 amp 220v circuit equipment, like a table saw, dust extraction, air compressor etc. 5 small mini splits (1 ton max each), 3 in the house and 2 in the pole barn. As of now the water heater, stove, dryer are on gas, I may swap them in the future. I figured the eg4 18k would be sufficient to start with or if there are other inverters that can connect to the panels, grid, generator and batteries and seamlessly swap between them I would consider those as well.

Thank you!

 

[AntronX]

Don't cut the pack like David Poz did. You can separate cell interconnect between cell 16 and 17 and keep the pack assembly intact. You then have 16S and 4S packs in each module. Connect those 4S sections across 4 modules and you have another 16S pack without physically destroying the module.