The battery pack consists in enclosing half of a Nissan Leaf's pack, i.e. 24 modules, in an aluminum box bolted to a tray (overview in the "Modular Garage Trays - Aug' 22" post). Each module contains 4 pouch cells arranged in a 2S2P configuration.
In case of an emergency with the cells, the aluminum box will contain a fire or other hazard for some time. Providing some time to the occupants to react, and possibly dump the tray outside on the ground.
The
30 x 26.5 x 9.75" (inside LWH) box was built out of a 3/16" aluminum
sheet cut and bent by a metal distributor. It is just large enough to
fit 12 modules sideways.
Li-Ion
pouch cells can swell under use and, if mounted on edge like here, the
electrolyte can pool at the bottom under the effect of gravity and
vehicle vibrations. Bad idea for long term reliability and pack integrity... 😱
To prevent that, each module needs to be mildly compressed by non-deformable 'bookends'. Like Nissan did in their pack. Sheet shims inserted against one of the box's walls, and 4 threaded rods, did the job. As seen in the pic above.
Warning: Tom & Jerry can survive deadly electrocutions. But you can't. And Li-ion batts can easily melt tools and spray molten metal. Do NOT engage in such activities without proper training and safety practices (insulated tools, gloves, glasses, emergency procedures, etc).
The quick connect / disconnect connector is an Anderson SB350.
So since our application only requires 250A max, with only a ~75% duty
cycle (cycling of both the induction cooktop & the air conditioner),
using this connector with 4/0 will be in spec and within
regulations.
The connector is mounted on the side of the box, as seen in the 1st pic above, or in the pic after next. It is loosely bolted to maintain alignment without strain
when mated, despite the minute shifts the box and tray will experience
during driving.
The other connector's half is rigidly mounted on one of
the walls supporting the dining area's floor:
Finally, the other 12 modules were installed, the busbars connected in a 3S16P config, and an aluminum lid closed the top. But we'll skip those details for now as this version is just a temporary pack solution.
Weighing 278lbs, sliding the tray in and out is very hard. I had to park the van downhill to push it in fully. This defeats the safety goal of being able to dump the tray in case of a pack emergency. The sliding strategy will be revisited in the next tray build.
Of course all this work will have to be tossed away and redone with LiFePo4 cells + BMS instead. As was realized in the Planning the Electrical & Energy System post.
Oh well, couldn't wait, adventure is calling. So be it for now. 12V loads will work but the 110V inverter won't 🙄
Update - Jan'23 This pack was completely rebuilt, with LFP cells and BMS. More details in Why LiFePo4 Cells for 12V ? and Battery Pack 2.0 with BMS done !
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