# Best way to parallel two Leaf halves



## PAXtss (Dec 16, 2017)

Neophyte here - I need some advice.

I just found and ordered the modules from a 2016 Leaf, all (48) 24 double modules which have 8 cells in each (see picture). I am wanting to create a 180V traction pack by putting the modules into two 180 volt packs.I see two ways of doing this:
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


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.
Any advice


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## brian_ (Feb 7, 2017)

PAXtss said:


> 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.


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## PAXtss (Dec 16, 2017)

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


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## PAXtss (Dec 16, 2017)

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

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


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## brian_ (Feb 7, 2017)

PAXtss said:


> 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.



PAXtss said:


> 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.


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## brian_ (Feb 7, 2017)

PAXtss said:


> 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.


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## brian_ (Feb 7, 2017)

PAXtss said:


> 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?


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## brian_ (Feb 7, 2017)

PAXtss said:


> ... (see picture)...





brian_ said:


> ...
> 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.



PAXtss said:


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


That worked.


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## PAXtss (Dec 16, 2017)

*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 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.

I am planning on a full fledged BMS 

Thanks for your posts Brian- I am always amazed at how much you know and I appreciate your sharing.

I see you posted something while I was working on this post, Does this way above work okay?


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## brian_ (Feb 7, 2017)

PAXtss said:


> *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.



PAXtss said:


> 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.


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## PAXtss (Dec 16, 2017)

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 - Then two double modules would have a four connection connector at one side and either a double connector or half of another Quad connector on other side. Picture is of my e-truck battery with that set up. It is hard to see connectors. On lower side from right is a double connector, a quad connector, another quad then a double to end stack.


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## brian_ (Feb 7, 2017)

PAXtss said:


> 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.


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## Kevin Sharpe (Jul 4, 2011)

brian_ said:


> I have no idea how easily the pairs of modules come apart (it is a two-module can, or just a pair of plates?)


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


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## brian_ (Feb 7, 2017)

Kevin Sharpe said:


> 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.


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## PAXtss (Dec 16, 2017)

Thanks for post Kevin,

I thought those were rivets looking (at picture) and I would have to drill them out but I see they appear to be removable and reusable.

Back to my original question about whether to do all parallel connections at lowest level which would be 4 cells or to parallel the half batteries like Wolf is doing. There are pro and con both ways and you (possibly) eliminate one for the lowest level paralleling. 

I am inclined to do the Wolf pack as it means every two cells have a BMS connection versa a BMS for 4 calls. But I don't know all the ins and outs of this. 

Thanks for help- You guys are great - helping and putting up with less technical folks.


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## Kevin Sharpe (Jul 4, 2011)

PAXtss said:


> I am inclined to do the Wolf pack as it means every two cells have a BMS connection versa a BMS for 4 calls. But I don't know all the ins and outs of this.


I like Wolf's approach and one of my friends intends to use his modified Leaf BMS when it becomes available.

I did build a 48kWh Leaf battery by paralleling modules (see here) and all the Leaf systems including the BMS worked fine 

In this photo you can see the Leaf GOM indicating 81 miles range at 50% SOC


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## PAXtss (Dec 16, 2017)

Great- parallel half packs (Wolf style) it is. I think I will just use off the shelf BMS with the ability to balance and keep an eye on everything. I did not get anything but the modules and a few power cables. I am a plug and install person and I do not have the technical skills to work out the Leaf setup. Computers were developed after I was born. Engineering school still had pencil type mechanical drawing courses. Punch card computers, too.

Kevin- thanks for link to the split screen van. I have been following for a while but did not remember about the battery part.


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## PAXtss (Dec 16, 2017)

I partially disassembled one of the Gen. 3 modules to see if it would be possible to reconfigure the double module for easy paralleling at the lowest level. The modules are double modules and put together to connect in series and I wanted to see what it would entail to separate the sub modules and turn one end to end so the terminals are both positive at one end and neg. at other and can be connected in parallel easily.
In previous post is a link to Kevin's dismantling a Gen2.
The Gen 3 is similar with the same compression type caps that are really easy to remove- a sharp chisel easily lifted these caps. I then lifted off the aluminum cover- it was glued but not very tightly and came up easily. 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. This is an expensive battery and I did not want to take a chance on damaging any part.
Pictures :
caps removed
close look at cells


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## brian_ (Feb 7, 2017)

PAXtss said:


> ... 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.


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## PAXtss (Dec 16, 2017)

After spending hours and bugging you guys I have come up with a way to parallel the modules. Reminder- this is the 2016 Leaf gen 3 battery which has two modules permanently attached together such that there is a positive and a negative terminals are each end of module. This is easy to connect in series but harder to connect in parallel. So I came up with some special busbars to connect the modules. Actually John at Thunderstruck clued me in on this.
Let me know if I screwed this up.


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## brian_ (Feb 7, 2017)

PAXtss said:


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


Clever!  Excellent use of adjacent and nearly adjacent terminals.


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## WJDijkstra (4 mo ago)

Hi everyone, I'm in the exact same situation as the original topic starter, using the 360v leaf pack (in my case the 24kwh one) at 180v. 
I would like to keep using the leaf bms, and I see a lot of references to Wolftronix and his setup, but I really can't find any details! His website doesn't show any modified leaf bms stuff, or am I missing something? I would love some help with this 

regards,
William


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