[brian_]

I just found and ordered the modules from a 2016 Leaf, all 48 double modules which have 8 cells in each (see picture).

Are you sure... in the original Leaf design, each of the 48 modules contains four cells, in a 2s2p configuration. That's 96s2p or 192 cells in total. Did the battery design - not just the capacity - change for 2016?

And what picture? There's nothing attached or linked.

 

[brian_]

These are 2016 - seller called them double modules. I wasn't sure it was correct but searched and found out these are later design - 30 KWH batteries. I bought 24 double module which is 8x24 cells= 192

That does look like one complete battery: the long stack of 24s(2s2p) which sits across the car under the back seat, eight modules (2s2p each) which are stacked two modules high under the floor in the areas where the rear seat occupants feet are, and sixteen modules (2s2p each) which are stacked four modules high under the front seat... just like the earlier years.

The issue is that paralleling the cells is tricky- not straight forward like older modules. I see I miss typed in first message - said 48 when it was 24- sorry

Each module has positive and negative terminals, plus one more between them which taps between the pairs of cells to give the BMS access at the lowest level. Nothing looks functionally different from the original Leaf modules, except that the modules other than those under the rear seat are all stacked in pairs apparently surrounded by metal plates, instead of metal around each individual module. I have no idea how easily the pairs of modules come apart (it is a two-module can, or just a pair of plates?), but electrically they appear to be completely separate, and so can be combined in the same ways as the original modules.

 

[brian_]

2- Series 48- 2P units and parallel them ? (2P48S)2P?
Two "Wolf" packs if I can steal his naming this. Easy configuration
Gives 2 cells per BMS unit 96 units.

Working from the highest level to the lowest level, I think this would be 2P(24s(2s2p))):

2 parallel strings of

(24 modules, each module consisting of

(2 groups in series with

2 cells in parallel in each group))​

Just like the WolfTronix Leaf module based 150V 65Ah battery pack..., except using 24 modules in series for 180 volts instead of 20 modules in series for 150 volts.

 

[brian_]

1- Parallel 4 cells and series the 48 pairs ?- 4P48S ?
The module configuration is not really compatible with this.
It gives 4 cells per BMS unit 48 units

Again working from the highest level to the lowest level, I think this would be 24s(2p(2s2p))):

24 sets in series of

(2 modules in parallel, each module consisting of

(2 groups in series with

2 cells in parallel in each group))​

I don't know why this would be incompatible with the module configuration. Keeping the modules in the physical pairs as they are already packaged, jumper the positives together and the negative together within each pair of modules to build each set. Series the sets together. Is the problem with the BMS?

 

[brian_]

... (see picture)...

...
And what picture? There's nothing attached or linked.

There actually was an image linked to the original post:

https://www.facebook.com/photo.php?fbid=10213636388876527&set=a.4618180725032.172558.1008054112&type=3&theater

... but the photo doesn't appear. I note that it is in Facebook, and I assume that it is not publicly readable, because when I open in link in a separate browser window I am prompted to sign into Facebook. When I sign in, I get a message saying that it is not available to me.

I will try picture again. I may need to find a teenager to show me how.

That worked.

 

[brian_]

If I understand the nomenclature correctly. You are saying build the two 180 packs and then parallel them together.
...
I think this is what Wolf is proposing but with four "Wolf packs" but he has some control circuit boards in there.

This would work with modules as is and would be easiest...

I'm saying that's your approach #2, and that it makes sense as a possible configuration... not that I think it's better or worse than the other approach. Yes, it is like what Wolftronix chose.

I read some where that it was best to do the parallel at lowest level. But that would mean 4 parallel cells for one BMS unit. It would also men taking the modules apart and reordering them- something I prefer not doing.

That would be your approach #1.

Production EVs tend to parallel at the lowest level, including the original configuration of this Leaf battery, and all Teslas. I assume that this is done to minimize the effect of a single cell failure.

If you want to parallel at the lowest level, I still don't see why there would be any need to open the modules, or even separate the pairs of modules. It doesn't look like there is any internal electrical connection between the two modules in a pair. The BMS might be more a challenge: as you said, it would only have 48 units to manage, but they would each have double the capacity expected by the BMS design... and the wires of the BMS harness wouldn't be the right length.

 

[brian_]

The issue that I see with the double modules is that they are set up to easily connect in series with short connectors. Looking at terminals- One is + tap - and the other one in module is - tap +. Easy to connect in series. To do in parallel will mean either strange connectors jumping over others or disassemble and reassemble so both are + tap -

That's what eventually dawned on me. It doesn't prevent the parallel connnection, but it does make the jumpers longer.

 

[brian_]

I think it would be worth disassembling one. Looking at the photo I think Nissan are using the same fastening technique they used on the "Gen 2" modules (see here). If I'm correct then you should be able to separate the two module easily and then reassemble them with the terminal polarity aligned to simplify the bus bars

Great details, thanks Kevin.

That does sound promising for reconfiguration, without changing the welded electrical connections, only reasonable structural parts.

So

• Gen 1: each 2s2p module is in a "sardine can" aluminum enclosure
• Gen 2: module is no longer entirely enclosed in metal, but only has aluminum end plates (and adhesive, and structural connecting hardware)
• "Gen 3" or 2016: two 2s2p modules are enclosed together in a pair of end plates
• 2018: not yet known

In a post in that thread, the pair of modules in the new-for-2016 version (total 8 cells, 2s(2s2p)) is referred to a module; this is the "double module" as discussed in this thread.

 

[brian_]

... The 8 cells are all stacked together and are glued together.
I quit at this point as I think I could separate the 4th and 5th cells but having to do 24 of them gave me pause.

Thanks for the information
The glued construction is unfortunate, both for configuration changes which would flip modules over, and for configuration changes which would use an odd number of modules in a group.

 

[brian_]

So I came up with some special busbars to connect the modules.

Clever! Excellent use of adjacent and nearly adjacent terminals.