Overall first impression and taking it apart.
The car on my driveway as arrived
As mentioned, since
in Australia they drive on the wrong side of the road, here is what the interior
looks like. The 12V
auxiliary battery was disconnected for the long journey. I charged it up, connected it
back, and turned on the key. The dash lit up, radio showed some Hebrew
characters on its display, SOC meter showed about 15% of the traction battery
capacity, but the main contactors did not engage. A bit disappointing, but not
very surprising. The only inconvenience this had caused was that I can't roll it
in and out of garage under its own power. I could take apart charging inlet and
attempt to charge traction pack with onboard NLG513 (this was trivial for me to
figure out), but with no traction there was no point.
Closer inspection
revealed "usual suspects" as main components: - UQM 450 AC drive, BRUSA NLG513-SA
charger, MES 400-1000 DC/DC converter, MES 70/6E vacuum pump, MES RM4 water heater
and Bosch water pump.
Interestingly - except for the AC drive, my business sells all these components
to the conversion market. Which reinforced my sense that these components used
by OEM are the most sensible selection for well engineered for mass production EV.
But the battery swapping mechanism was new to me and it is unique to this
vehicle. So I raised it to find out how exactly battery swapping system was designed.
I must say this is
quite amazing piece of engineering. From what it looks like, it was quite an
expensive system. No wonder that this vehicle turn out cost far more than it was
anticipated.
Basically a cam
system around the car, activated from single location on the left side, is
linked using shafts and U-joints to four large claws that grab the pack by its
corners and hold it
underneath the car. The pack is guided in and out by two large alignment pins
sliding into a mating tubes mounted
up front to the body.
Here is close up
photo of one of the claws open. The battery can be unsnapped in about 15-20
seconds with this ingenious mechanism. All I had to do is to crank the actuator
(worm drive) head, seen on the photo above this one.
Guiding
alignment pins welded to the the machined aluminum battery tray. Entire tray has
grooves and battery modules attachment features CNC milled in it. Quite a work
of art. Massive steel claw on top is also visible.
Close up of the
battery tray. The alignment guide and the bracket with retaining pin.
The battery is
shaped after the standard cavity in Nissan's underbody.
The battery consists
of 8 modules manufactured by A123 Systems. There are 3 module sizes used in this
vehicle, but its clever packaging allows to stack any number of cells using
standard heat sink plates, plastic covers and the BMS components. The long
modules have 3P16S arrangement, the medium ones are 3P11S and the short ones are
3P6S.
The cell type A123
uses here is LiIon AMP20M1HD-A pouch cells produced in South Korea. Cell's nominal
voltage is 3.3V, nominal capacity
is 19.5Ah. A I mentioned, there are three sizes of battery modules used in Qashqai
- 16 cells (3 modules), 11 cells (2 modules) and 6 cells (3 modules). A "cell"
here actually consists of three 19.5Ah cells in parallel. Quick calculation on the back of a napkin reveals that
this entire battery then has got a total of 3*3*16+2*3*11+3*3*6=264 cells. With 3P
arrangement in all modules this means 264/3=88 cells in series. At 3.3V nominal
voltage that's 290.4V pack and at 19.5*3=58.5 Ah nominal capacity it's got 290.4
V * 58.5 Ah = ~17 kWh
energy contents. That's about 71% of Nissan Leaf's battery. Assuming same
240Wh/mile consumption as Leaf claims (at 35mph speeds), that translates to
70.8 miles range, or ~56 miles at freeway speeds. Not spectacular, but keep in
mind that the battery is designed to be swappable and perhaps it was calculated that a customer
can always get to the nearest swapping station with this kind of range. Anyway,
this was interesting to find out, but it was not the point of disassembly...
The power cables snake around the tray and connect the modules in series. The pack has emergency disconnect in about [electrical] middle, so the cabling appears more complicated than plain series connection of all the modules. The BMS network (black looms) is routed separately from power cables to reduce interference. Naturally, all the comms are implemented via CAN.
Main contactors and A123's current sensor module.
Everything is standard as expected. You can see precharge resistor above
smaller precharge contactor. (There are actually two resistors in parallel, one below the
other). Granted, I reconstructed the schematic of this block, but did not
discover anything surprising or unusual - if I were to design this circuit, that's
exactly how I would wire it all as well. The only component on the left (partially
visible on the photo) is current measurement module - you can see that the pack
negative cable connected to a bus bar fed through a Hall effect current sensor
is entering this box. I'll take the box apart, but since I have designed EVision
system that required accurate current sensing, I already have pretty clear idea what's inside this module.
Connections to the UQM power inverter. Hi quality metal feed through glands and
solid aluminum blocks in the enclosed compartment - again solid engineering at
its core.
Zoomed in detail of the photo above.
Fragment of the contactor box - a bus bar fed feed through the Hall sensor into
the A123 precision current measurement block.
All battery modules are attached to the fiberglass tray through this stainless
steel hardware. Apparent simplicity of appearance is a result of great
experience in engineering such things - these parts of the battery design are
often overlooked.
Sanden integrated A/C compressor+motor+inverter - self contained unit
specifically designed for use in an EV. I might take advantage of it in my
conversion project, but first I have to determine its DC voltage operating
limits. I must say I was lucky that this vehicle was an engineering prototype,
there are labels, arrows, notes and clues written with a marker on many
components, cables, blocks, connectors etc., which helped to identify what I'm
looking at. If the car was a production model, deciphering which cable goes to
what module would be far more difficult. In the case of this unit it is very
clear though: HV orange cables (+ and - were marked by somebody at assembly,
thank you...), and 4 signal wires two of which are twisted, so 12V aux power and
CAN bus.
After all the modules were taken off the tray, each
was perked up with external power supply to about 60% SOC for long storage. It
is unlikely I can get hold of more of these modules, so it is not enough for my
conversion progress in progress, and I'm not sure I'd se this type of battery
anyway but these packs may be useful for the BMS tests and as something as a
range extender trailer. The BMS PCBs would be replaced with my own, but it is
hardly worth the effort to design them from scratch to fit in place of stock
PCBs for just one off battery system. For now will wait and see what kind of use
these modules can be put in.
Power distribution box. Everything is heavy duty there.
Back cover of the PDU laid on top of BRUSA NLG513
battery charger - thanks for sharing the wiring!