Both controller shut down due to low NVRAM battery

• Two new controllers have just been installed
• When booting ONTAP, the following message appears on CLI

WARNING:  The battery is unfit to retain data during a power
          outage.  This is likely because the battery is
          discharged but could be due to other temporary
          conditions.
          When the battery is ready, the boot process will
          complete and services will be engaged.
          To override this delay, press 'c' followed by 'Enter'

• The warning is ignored and ONTAP is forced to boot

CAUTION: Using this appliance without NVRAM
         battery backup coupled with a power
         failure condition CAN CAUSE DATA LOSS.

Are you sure you want to continue (y or n)? y

Proceeding without NVRAM battery backup.

• Controllers halt with the following message

[node-01:monitor.shutdown.emergency:EMERGENCY]: Emergency shutdown: Environmental Reason Shutdown (Battery remain capacity critical)