Pack Gravimetric Energy Density

Pack Gravimetric Energy Density has the units Wh/kg and is a key pack metric. The optimum metric is a high Wh/kg. Hence:

  • High nominal voltage
  • High Ah capacity
  • Low mass

The best you can achieve will be less than or equal to the cell Wh/kg that the pack is made from.

Perhaps the simplest of the battery metrics as the capacity of the cell is fairly easy to measure and the mass is just a set of scales.

The only note of caution is the discharge rate at which the cell Ah capacity has been measured. For automotive C/5 to C/3 is quite representative for a range test. However, for a phone or laptop C/10 is perhaps closer. Most cell capacities are quoted by manufacturers at C/10.

Plotting this energy density versus total energy in the pack is as expected.

battery pack energy density versus total energy
Data from the Battery Pack Database

If you have more data that you would like to share on this list then drop us a line via the contact page.

Electrified Aircraft Propulsion Targets

In aircraft the gravimetric energy density is one of the key targets at pack level. As of 2022 the 400Wh/kg target from NASA is a very tough target when automotive packs are achieving ~170Wh/kg.

NASA electrified aircraft propulsion system targets

NASA state in their November 2021 presentation that they have the following requirements for the battery pack:

  • 400 Wh/kg required at the system level
  • 1000’s of cycles
  • Extremely high power requirements (C-rates) during takeoff and landing
  • Cruise power for long range flights
  • High reliability, limited maintenance
  • Improved safety for thermal runaway events

battery pack mass versus total energy for all packs in the database and BMW picked out in red

Battery Pack Database

An excel file with hundreds of battery packs and thousands of datapoints. Check your design against other designs to ensure the metrics stand out from the crowd.

Battery Pack Mass Estimation

This is one of our calculators that lets you estimate the mass of the battery pack based on the cell mass and total energy content.

This applies to automotive HV battery packs.

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