WiseGuy wrote:Sigh! AndyH: to get the true maximum installed capacity of a battery pack (in Wh), you multiply the nominal cell voltage with the max cell capacity and then the total number of cells (regardless if they are in series or parallel). For the Leaf, this gives us 24kWh.
The fact that we only use a limited voltage window to prolong life and enable power capability, means that the useable energy is LESS than the 24kWh install capacity.
I suggest you do some maths & "design" your own pack using the cell data of the Leaf (or any other cell). You'll quickly realise that 24kWh is the true installed capacity (unless there's an error on the published discharge curve ...)
Thank you for your advise WiseGuy.
The fact is I DO work with lithium daily, build packs, and perform road and bench testing. I do understand the math. I'm also capable of reading the display from the equipment I use to run charge and discharge tests.
If one has a 1 litre container but chooses to only use 80% of the capacity, then I completely agree with your assertion that they would be only drinking 800ml of water.
However...if one starts with a 1.25l container and uses 80% of the capacity, the thirsty lab tech can drink 1l of water.
The info published by AESC show the derated, lower capacity, long-life numbers - not the ultimate capacity of the cells. We know that because we have the allowable voltage range from the car's management system - and the numbers used in the AESC graphs match the voltage limits used in the car. We also know that trying to pull 100% capacity from a lithium cell guarantees a very, very short cycle life - not good for the folks holding the warranty.
In addition, Nissan reports 24kWh usable with a total capacity that is proprietary. AESC reports 24kWh. End-users that have run the battery flat use more than 26kWh to recharge. Ingineer has pulled info on cell capacity from the car using the Nissan scan tool - this also confirms an end-user capacity in excess of 24kWh.