drees said:
Now the question is whether they will produce the current chemistry for the '16 LEAF S, or if they will package fewer higher density modules.
Right now each of the 48 modules holds about 0.5 kWh of energy. Assuming that they keep the packaging the same (and it makes very little sense to change packaging for a single model year), a 30 kWh pack will hold about 0.625 kWh. Nissan could use the new higher density cells with the same packaging, but only 38 of them for 23.75 kWh, but this would also reduce pack voltage by a significant amount. So it seems that Nissan would simply continue using the current "Lizard" chemistry for the 24 kWh LEAF rather than re-package the new cell in a 80% capacity module configuration. But who knows - maybe they will? We'll find out soon enough.
I expect that the modules will all be the same in a given model year, so I suspect the S will simply have fewer modules.
If that is correct, then there are a couple of related questions:
- Will the 2016 LEAF S have the same capacity as the 2015s, but lower weight AND lower maximum power due to the reduced voltage?
- Does reduced voltage mean reduced heater power in very cold weather?
- Does reduced voltage have any deleterious effects on the life of the compressor in the air conditioner.
But, perhaps more importantly:
- How will Nissan offer increased capacity for 2017 in increments other than double the 30 kWh (or perhaps double the 24 kWh)? Let's say that 30 kWh gets you the same voltage as today's LEAF. It seems clear that 60 kWh could easily be offered, but what if Nissan cannot shoehorn that many (96) modules into the vehicle? Would they offer a version with, say, 76 modules providing ~47.5 kWh, but both higher weight AND lower maximum acceleration and lower heater wattage in extreme cold.
The heater thing could be easily addressed at the factory by simply changing the resistance of the heater for models with only 38 modules in series, but what about the compressor motor in the air conditioner?
One answer could be that Nissan will change the module configurations from 2+2 to a single series string of four modules. Then they could offer a 24 kWh model with 2 strings of 19 modules, a 30 kWh model with 2 strings of 24 modules and a 45 kWh model with three strings of 24 modules. But modules with four cells in series would each need five terminals instead of just three, so amount of wiring would be increased significantly to support the BMS, etc.
Another answer may be to go with larger modules, like 3+2 modules like GM has in the Volt.
There are more questions, but I think you get the idea: If Nissan starts to offer battery options with different output voltages to provided different capacity options, then that has quite a few knock-on effects.
I'll be interested to see how Nissan (and other manufacturers) handle the issue of offering various capacities which are not multiples of some base value.
