BMS extensions
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@isak, I’m working on plans to do a conversion with a 62kwh pack.
I need to split it in two, hence I need to extend the BMS wires.
Do you have any experience splitting the pack and can the extension harnesses, you sell, be used.
Any good suggestions, ideas or previous experience with the 62kwh pack is greatly appreciated. -
My project used a split 60kWh. Things to note -
Keep the split in the centre of the pack as Nissan designed it.
My split has 2m of HV and BMS extension. Under load, if I accelerate hard, LeafSpy shows a large voltage drop on the first cell of the 2nd pack. I guess this is because of the extra resistance in the cable that the BMS wasn’t expecting. This can lead to a momentary loss of power. Normal acceleration is fine though.
I’ve done 3500 miles since converting. -
@ianlighting thanks for the reply.
Did you use Isaks extension harness.? It’s difficult to find much info on the 62kwh pack so
I’m trying to figure out the harness layout and if ISaks harness can be used in a similar fashion as for the older packs.
I’ll check out you build thread a bit more for inspiration
The voltage drop you mention could it be a connection issue rather than the HV cable itself?
I assume the cells are well balanced and no issues with that particular first cell in pack 2. -
No, I’m sure it’s not a cell issue. Not possible to easily disprove it’s the cable without taking the car apart, but I know a similar situation has been mentioned elsewhere.
I haven’t checked recently, but last time I looked, the BMS extension cables they sell would not work with the 60 / 62kWh (same pack as far as I know but Nissan changed either the label or the BMS maximum at some point). The older 24 - 40 packs all had the same connectors. But the 60 has 3 different types depending on module size.
When I did my build, I collated everything from the entire internet (which wasn’t much) and dumped it into a thread on OpenInverter where I took mine apart. That’s separate from my build thread there.
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Great build page you’ve made…I browsed through and im quite impressed with your approach and ability to solve the problem you’ve been facing with, what you express yourself, limited knowledge and experience.
I’m sure it has been an exciting journey!!!
Do you have pictures of the BMS extensions you made and what about the battery boxes / final layout and orientation of the modules. I couldn’t find much af these details on you page, but maybe you have pictures and other details worth to share? -
Yeah, it was a learning curve. I’m glad I survived and am happy with the result. Now done 3500 miles without exploding
This is my old working doc for the BMS extensions. It’s pretty rough because it was only for my own consumption. Hopefully you can open ok.
But you can see the info for extending for modules 11 to 16.
Note I did a slightly odd thing, which makes sense to me. The halfway point should be after module 8. I kept the service disconnect there. But I actually added modules 9 and 10 into the same box #1 with 1 - 8. I wanted more weight and volume at the back.
Then modules 11 - 16 are box #2. The extensions of main HV and BMS are for these.
The voltage drop I get sometimes is at module 9, on the first cell after my cable extension.
I don’t have great photos but will add what I have.
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Photos show
Box 1
M1, M2, S3 (on top of M1)
S4, S5, S6 (along back of box, but placed on their backside facing up)
T7, T8, cable to service disconnect.
T9, T10,Cable ext
Box 2
Fuse, S11, S12, S13, S14, M15, M16
cable back to box 1.