What makes a good electric car battery?

BMW i3 battery interior

BMW i3 has what I think a great battery pack.

 

I’ll list here why I think that:

  1. Samsung SDI cells, these 60 Ah NMC cells have a great durability.
  2. Cells disposition is what it should always be. Side by side, for better heat dissipation. Having cells on top of each other is not a good idea, the top cells will get hot and degrade faster.
  3. TMS (Thermal Management System) for keeping the battery at recommended temperature is very important.
  4. KISS (Keep It Simple, Stupid) principle, since it only has 96 cells all connected in series, none in parallel.

 

In the other side, we have Nissan Leaf 24 kWh battery. For me it’s the electric car with the worst battery. Nissan engineers really made a mess when they planned it.

 

Nissan Leaf 24 kWh battery

 

  1. AESC cells that use LMO chemistry known for having a low lifespan.
  2. Cells disposition is what it shouldn’t be. Having cells on top of each other is not a good idea, the top cells will get hot and degrade faster. This is even worse since the battery doesn’t have a TMS.
  3. TMS (Thermal Management System) for keeping the battery at recommended temperature is very important and Nissan Leaf doesn’t have it.
  4. This is not very important but it would help, the KISS (Keep It Simple, Stupid) principle. With battery packs that have parallel cells, it only takes one bad cell to discharge the others it’s connected to.

 

The good news is that MY 2016 Nissan Leaf with 30 kWh battery will change its cells from LMO chemistry to NMC. That fact only made Nissan confident enough to improve the battery’s warranty to eight years or 160.000 km.

Leave a Reply