How much battery capacity is ideal for your LEAF?

[DanCar]

Here is an article about doubling battery range for next year.
http://insideevs.com/150-mile-nissan-leaf-could-become-reality-so-too-could-a-76-mile-chevy-volt/" onclick="window.open(this.href);return false;

 

[KJD]

I intend to point Nissan to this thread anyway.

Did anyone from Nissan look at the survey results ?

 

[TonyWilliams]

I suspect that any range increase that Nissan would actually enact would be conservative (like 30kWh to 36kWh max). I'm confident they've learned their lessons in marketing, and won't call them 200 mile / 300km cars just because they can game the Japanese government range tests at super low speed. I challenge them to "think leadership", and go directly to a 36kWh and 48kWh option.

36kWh is electrically easy because the add-on 12kWh pack can be the exact same cells as the existing pack, but with just 96 cells all in series 96 * 4.1 volts per cell = 393.6 volts). The existing 24kWh pack is 96 cell pairs (two cells in parallel) for a total of 192 cells.

Logically, the BMS would operate all 288 cells as 3 cells in parallel per module, 96 modules in series. Just throwing a 12kWh extra pack in parallel will have those cells working "harder" than an integrated pack, I think.

The same holds true for a 48kWh pack. They could have 4 cells in parallel per module (and fit perfectly in the existing module case that currently holds two cells in parallel and two in series). So, 48kWh might be the easiest cells to build with existing equipment and the hardest to package in the car due to physical size and weight!!!

Naturally, I can only hope they do this with a far, far lighter battery (in kWh per pound/kg), but the existing battery would be ok with even a rudimentary cooling system (air conditioned cooling in an insulated case).

For onboard charging, consider dual J1772 AC ports, and make each charger capable of a full 30 amps at up to >>> 250 Volts <<< for 7.5kW * 2 chargers = 15kW AC from any two existing J1772 AC public charger stations in the world.

For quick DC charging, get the CHAdeMO standard up to the full 200 amps (vice the existing 125 amps), so that it can be advertised as 100kW (even though it will only put slightly less than 400v * 200a = 80kW in max). On a 48kWh pack,the charge rate at 80kW is actually less than the current rate of 400v * 120a = 48kW on a 24kW pack (2C).

THE BATTERY NEEDS COOLING TO DO DC CHARGING, PARTICULARLY MORE THAN ONCE PER DAY.

 

[DaveEV]

36kWh is electrically easy because the add-on 12kWh pack can be the exact same cells as the existing pack, but with just 96 cells all in series 96 * 4.1 volts per cell = 393.6 volts). The existing 24kWh pack is 96 cell pairs (two cells in parallel) for a total of 192 cells.

Logically, the BMS would operate all 288 cells as 3 cells in parallel per module, 96 modules in series. Just throwing a 12kWh extra pack in parallel will have those cells working "harder" than an integrated pack, I think.

No, the load on each pack should be similar. The 12 kWh pack will have higher internal resistance, so the 24 kWh pack would support more of the load. But still, because of the potential issues with such a design, I can't see it being used in a production vehicle. Maybe I'm wrong. That's one of the drawback of large format cells compared to the Tesla approach. But even then Tesla appears to be keeping module sizes the same, just changing the number of modules (as evidenced by the lower pack voltage of 60 kWh cars compared to 85 kWh cars).

I suspect that Nissan will want to keep the battery module the same size/format to maximize production economies of scale - the question will be what's the most effective way to package those batteries in multiple pack sizes. Perhaps a modest increase in cell capacity combined with an increase in the number of cells. Really need to know what the max/min operating voltages of the various components are to make educated guesses. Say 54 modules in series which would bump up max voltage up around 445V (still under max CHAdeMO voltage) which is a 12.5% increase in capacity, combined with a 15% increase in energy density of the cells themselves would result in a pack with 30% more overall capacity (31 kWh). For a 24 kWh pack, only use 38 modules.

I have to think there's a good reason there aren't any packs over the low 400V range, though in any production plug-in vehicles that I am aware of.