Leaf Cell Powerwall Configuration Advice

Hello all,

Steve Jackson here, and I am hoping to get some help determining configuration for my leaf cells into a usable powerwall.

So,

I have 24 Leaf Cells, Gen2 64ah, 7.2v 2s, that I want to configure into a pack.
https://www.ebay.com/itm/Nissan-Lea...859615?hash=item1a5b79d09f:g:H0MAAOSwsB9blq4d

My Inverter is an AIMS 6000 watt nom./18000 watt peak Pure Sine, 110/120v only
https://www.aimscorp.net/6000-Watt-Power-Inverter-Charger-48-Volt-to-120-Volt.html

Plus a 48v 60 Amp Charge controller with ability to charge lithium.
https://www.amazon.com/gp/product/B0787WYJYX/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1

Plus 14 Newpowa 100w solar panels @ 17.2v max, 5.81A max
https://www.amazon.com/gp/product/B0725RZ22H/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

I will be running a small portable office with:
x6 T5 LED light bars @ 15 watts each
4000btu tiny 110v AC unit. (Infrequently for 30-60 mins at a time, only during the daytime)
Security system with 6 cameras @ 20 watts each
Dorm Style Mini Fridge (Low power, Smallest one, just for water and sodas)
Small DC pump for Flushing toilet and hand washing
Occasional Small Air Compressor use
Occasional Laptop and Cell Charging

Here are my Questions:
1. Should I go with 4P6S or 3P7S?
2. Will my Inverter with a 42v low volt cut off handle a 4P6S Setup?
3. Is a BMS required for my use case? Or can I do a weekly manual check/balance and be ok for the first year? (Till I can afford a Battruim Leafmon setup)
4. Where does one obtain copper bus Bars?
5. How thick do they need to be?
6. Can you help me diagram the connections for a 4P6S and a 3P7S configuration? There isn't much online for this that I can find. The Split config of these cells is a bit confusing.
7. Where EXACTLY do you fuse something like this? Only at the battery? Positive or Negative?
8. Where does the EARTH grounding rod go in this scenario? Only to the Ground on the output of the 110/120v AC from the Inverter? Nowhere else?

Sorry, I know its a lot, but I am new at this.

Thanks in advance for ANY help or diagrams you can assist me with!

Steve Jackson
Owner
Million Acre Farms

That's a lot of questions for one thread, you might be better off doing a LOT of reading and ask a few separate ones, perhaps in seperate threads - however much of what you've asked has already been answered on here, you'll pick up a lot of related knowledge whilst looking for specific answers.

I'm doing similar with multiple (entire) packs, and currently have a 6S test pack running, there's a few threads on here relating to that.

With reference to PE and grounding rods, you'll need to consult, and likely pay, someone local to you who is properly qualified and approved, in whatever Country you live, to do that job - the test equipment just to test that will be significant.

And also please read the FAQ

And also, from the other thread:

zurkeyon said:

Hello all,

I have questions but I need to post links to get them answered.

This is me posting my one post.

Steve Jackson
Owner
Million Acre Farms

Click to expand...

Korishan said:

You can post and then go back and edit the post

Click to expand...

FAQ Answered 0.0% of my questions...

zurkeyon said:

FAQ Answered 0.0% of my questions...

Click to expand...

The FAQ is a good start for those that do not have an electrical Background and do catch the really basic questions we used to get all the time. The fact that you are above those answers means you have already done your research. As for specific questions we will gladly answer those.

Cheers

Im really reluctant to give much detailed advice, I'd rather point folks at learning content so they can have a lengthy read, and hopfully come back with more informed and less general questions.

There's a lot of scope for folks doing harm if they simply follow a series of random answers without some depth of knowledge.

Questions about earth rods are an early warning, the usual retort will be "I'll get it professionally installed and tested"

1. Should I go with 4P6S or 3P7S?
With a Range of 42 -64V is 14s (leaf batteries are 2s each so 7s) would be Ideal

2. Will my Inverter with a 42v low volt cut off handle a 4P6S Setup? yes but you will not get the full capacity out of your batteries

3. Is a BMS required for my use case? Or can I do a weekly manual check/balance and be ok for the first year? (Till I can afford a Battruim Leafmon setup)
You do not need a BMS if you are going to be managing it manually. but that requires constant watch. IMO. but I think a BMS with the ability to isolate your batteries if needed is a must.

4. Where does one obtain copper bus Bars? I get mine from a electrical supply for industrial uses but I have also flattened copper water pipe which works as well

5. How thick do they need to be? Depends on the current (max) you are going to run

6. Can you help me diagram the connections for a 4P6S and a 3P7S configuration? There isn't much online for this that I can find. The Split config of these cells is a bit confusing. Yes post after



7. Where EXACTLY do you fuse something like this? Only at the battery? Positive or Negative?
These are different than 18650 and most do not fuse each cell but the entire pack in a breaker style unit

8. Where does the EARTH grounding rod go in this scenario? Only to the Ground on the output of the 110/120v AC from the Inverter? Nowhere else? Not nothin here

1. Agree with Jdeadman. 7s will probably give a better woirking voltage range for the charge level and the cut-off should be ok under higher load, which is when the battery voltage will sag a bit due to internal resistance. The upper charge limit on the AIMS would allow a 58.8V (4.2V per cell) charge level.
2. As above
3. Yes - all used battery systems benefit from a BMS unless you want to change your name to BMS and be the BMS
4. As per Jdeadman. Aluminium can also be used but you need a larger bar.
5. Similar overall cross sectional area compared to a copper wire - i.e. thick enough to handle the current flow without heating. Then add on the material loss that would occur from any holes that are drilled through for bolting. I'e, 100A rated (maximum between any two points on the bar) would be around 24mm2 (2mm x 12mm) the cross sectional area loss from a M8 hole is then 8mmx2mm or 16mm2 so you need 40mm2 or 2x20mm as an absolute minimum for 100A and M8 fixing. How you connect to the bar also needs consideration os to the required contact area to get a good join, so 20mm may be too narrow. Depends on what and how your connecting to it.
6. As per Jdeadman
7. Positive side is normally fused to prevent ground loop / earthing issues. Fused at most points that differing size wires / rated equipment is used. Specific ratings and placing will depend on what you implement and expect (i.e. do you want to try and pull 6000W from the cells). The battery pack can be without fuses between cells/parallel packs as per jdeadman.
8. As per Jdeadman

zurkeyon said:

FAQ Answered 0.0% of my questions...

Click to expand...

You obviously didn't read everything. If so, you would of noticed the relationship with battery arrangement, electrical jargon, layouts, etc.

Specifically, I highly doubt your cells are arranged in XpYs configuration. Asking about 3p vs 4p is another part. Try to go with the highest parallel that you can, regardless of how many are in series. Reason is, Parallel = Ampacity.
Fuses are discussed in the FAQ as well.

MANY of your other questions have already been answered throughout the forum by several others. With great detail in some of them.

The leaf packs are already 2s so this may create some confuson with the way that the people on the site usually describe a system. On a cell basis your 7 series packs system would actually be 14s in the terms used on the site.

Wait, what?

So, they designed a multi-series setup?

Lemme see if I get this right. They designed it with the cells being 2s2+p, then connected those in series with 7 others to get 14s?
If that's right, then it'd still be 14s2+p, as it'd be like several of the builders here build 2 separate strings, then connect each pack in parallel with the next string.

And jdeadmans picture shows our conventional way we state it. Unless his is completely different than what is actually in the leaf skid. hrmm......

corrention .The leaf cans have four pouch cells 2 in series 2 in parallel.

I am assuming the original 6s pr 7s was meaning 6 cans or 7 cans..

Yes and Yes the Center point is just a balance port and not really designed for high current

jdeadman said:

Yes and Yes the Center point is just a balance port and not really designed for high current

Click to expand...

When compared to the primary terminals, and based on the expected current across the mains in its original application, that's correct, but the central balance terminal is still fairly substantial - approx 13mm square for the balance and 20mm for the main set.

jdeadman and completelycharged Thanks to you BOTH.

That was exactly what I was looking for!

I VERY much appreciate your efforts.

Should get me where I need to be.

Seriously,

Thank you!