Nissan Leaf battery for offgrid storage

[vast]

I intend to buy a Leaf battery for my 48V off grid system.
My setup:
- Midnite Classic 150 solar charger
- 16s 100Ah Sinopoly battery
- PIP4048 inverter (made by Voltronic Power from Taiwan and rebranded by MPP Solar).

In respect from this link , a single cell have an average voltage of 3.8V, and 3.65-4.1V (or maybe 4.0V for safety) range for 80% of the capacity. That mean a 2p2s pack have 7.6V average voltage. We can connect:
- 6s: 6 x 7.6 = 45.6V
- 7s: 7 x 7.6 = 53.2V
- 8s: 8 x 7.6 = 60.8V

Midnite can charge between 12-93V, so there is no problem to handle even 8s. But my concern is with the inverter for LVD, because max. cut-off disconnect is 48V.

[Mike90250]

.......my concern is with the inverter for LVD, because max. cut-off disconnect is 48V.

Most 48V inverters have a LVD of 46V, and max voltage of 70V

And when you pull a battery out of a car, you loose the BMS that keeps the battery safe and healthy

[Sunking]

I intend to buy a Leaf battery for my 48V off grid system.
My setup:
- Midnite Classic 150 solar charger
- 16s 100Ah Sinopoly battery
- PIP4048 inverter (made by Voltronic Power from Taiwan and rebranded by MPP Solar).

You sure are confused. What does a Sinopoly LFP battery have to do with a Leaf NMC battery?

Answer = Nothing. Completely incompatible with each other. To use a Leaf battery will require 14S and charged to 58.8 volts and Floated at roughly 56 volts, or terminated when charged. 12S or 16S will not work.

[vast]

I'm not confused. I will not mixed Sinopoly with Leaf.

My problem is: range limit for LVD in my inverter is 40-48V. So, if low limit for cell is 3.65V, that mean 51.1V for 14s, but 43.8V for 12s. For 12s I will charge at 50.4V and float at 48V.

[vast]

Another question is: do I need to do BB for these Leaf cells or I can connect directly to charger and inverter after dismantle?

I have Midnite + Shunt + Whizbang jr and I can know SOC.

[Tesla]

Most 48V inverters have a LVD of 46V, and max voltage of 70V

And when you pull a battery out of a car, you loose the BMS that keeps the battery safe and healthy

So what does one do, are there BMS for DIY solar ? (newbie)

[Mike90250]

Another question is: do I need to do BB for these Leaf cells or I can connect directly to charger and inverter after dismantle?

I have Midnite + Shunt + Whizbang jr and I can know SOC.

What is BB ? Battery Bank ? No, the cells make their own bank. You are well on your way to making a fire in your workshop. The questions you are asking, show you have an awful lot of gaps in your knowledge. what you are asking, is like "Do I add the glycerine to the acid, or acid to glycerine" and "is it shaken, or stirred ?"

We can answer the questions you ask, but the questions you don't know to ask, what can we do ? You are so out of your league.
First stop is to go to the Battery University and look up the chemistry of Li batteries, what sort of cells are you getting out of the Leaf, read up on the care of them, proper charge setpoints, thermal limits and all that.

http://batteryuniversity.com/index.php/learn/article/types_of_lithium_ion

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

[Raul]

Mike, I'm sure he meant botom balance. Once out the car the cell will need some sort of commissioning and then put into a bank.
I think he was hinted at that.

[Sunking]

My problem is: range limit for LVD in my inverter is 40-48V. So, if low limit for cell is 3.65V, that mean 51.1V for 14s, but 43.8V for 12s. For 12s I will charge at 50.4V and float at 48V.

This is the crux of the problem. NMC operating range is 3.2 to 4.2 vpc

1. Even though technically 12S you could make work, does not work very well because your operating voltage range is 38.4 to 50.4 volts. Most Inverters made to work with Pb batteries LVD operates at 42 to 44 volts. NMC batteries have a well defined voltage charge/discharge curve meaning you can with some accuracy determine SOC from voltage. If your LVD operates at 42 to 44 volts means you cannot access the last 30 to 50% power left in the batteries. Additionally operating at 12S has roughly 15% less capacity than 14S which means you shoot yourself in both feet. I mean big hole in your feet. Operating at 14 S is more than twice the capacity of 12S. Understand?

2. 14S range is 44.8 to 58.8 and can be made to work, but you risk over discharge if your Inverter LVD is equal or less than 44 volts. You would have to be able to raise that LVD voltage up, or have a Voltage Monitor and an external relay to act as an auxiliary LVD .

So the issue or challenge is the Inverters and to some degree Chargers. Most equipment out there is made to work with Pb voltage range and the only Lithium Ion battery compatible with that is LFP aka LiFePO4. So to make any other Lithium chemistry workable your Inverter and Chargers must be able to be reconfigured with either software or firmware.

[vast]

Now is evening in Romania, and I have more time to explain what I have in my mind. As you can see, English is not my native language, so please be patient with me if I made some mistakes.


Hi Raul! You understood me very well with all.


@ Mike,
BB = Bottom Balance.


@ Sunking,
I read a lot of your posts about LFP battery from 3 years ago. I learn a lot from you - thank you and my respects!
I use Sinopoly 100Ah@48V for 2 years (I know that you prefer Calb, but Sinopoly had an offer when I bought it). Because I can use only 4 from 5kWh, which is not enough for me sometimes, I am looking for an alternative low cost.

1.-2. I understood perfectly what you say, and I agree with you.

About LVD: I can setup the Low DC Cut-Off Voltage on inverter from 40.0 to 48.0V, increment in 0.1V steps. So, there is no problem to setup 44.8V LVD for 14S.

Question 1: 3.2V/cell is it not to low? What is the limit for cut-off voltage?

Question 2: Before connecting them together, it is necessary to perform a Bottom Balance?

Thank you for your time.

[Sunking]

Question 1: 3.2V/cell is it not to low? What is the limit for cut-off voltage?

No it is very conservative for Nissan Leaf cells. Death is at 2.5 volts. Some cut off at 3.5. Nissan Turtle mode is 3.2

Question 2: Before connecting them together, it is necessary to perform a Bottom Balance?

Makes no difference how you balance at the top, bottom, of mid balance. All three are done exactly the same way. With Leaf Cells being NMC balance is not much of an issue and can be easily Mid Balanced. You start by connecting all modules in Parallel and walk away for a day. After they are voltage balanced (Mid Balanced), leave them in parallel and either Top Balance by charging to 8.4 volts per module, or Discharge to 5.2 volts per module for Bottom Balance. If you Mid Balance no action required after they are voltage balanced. When done wire in series and you are ready to go.

FWIW DIY EV builders who use Leaf Modules Mid Balance just like Nissan does and all other commercial EV manufactures use.

Charge to 57.4 volts @ 14S (4.1 vpc)
LVD at 44.8 volts @ 14S (3.2 vpc)

[vast]

Sunking, what could be happens if I connect 16S and charge with Midnite to 65.6 volts (4.1 vpc) and LVD at 48 volts (3 vpc)?
Leaf 24 kWh battery pack have 48 modules and I would like to use all of it. If i use 14S, that mean 6 modules are not used.

For 14S, what is the voltage for float?

[Sunking]

Sunking, what could be happens if I connect 16S and charge with Midnite to 65.6 volts (4.1 vpc) and LVD at 48 volts (3 vpc)?

Your 48 volt Inverter most likely will throw a fit and shutdown from over voltage. Might even let the magic smoke out and magically turn itself into a boat anchor. 3 vpc is too low and risky.

For 14S, what is the voltage for float?

4.1 ish vpc.

You need to be absolutely certain your Inverter can handle the odd voltages.

[vast]

I check again my inverter specs and I will stay away from 16S because have a High DC Cut-Off at 60V.

Thank you for your time.

[Sunking]

You are welcome.