Users Guide

Battery
A battery is required to provide backup power to copy contents from DRAM to flash. Although JEDEC based NVDIMM-Ns can
utilize Super Caps as backup power, DellEMC’s battery is a centralized power solution that provides a more compact, reliable,
and integrated power source. Power delivery is integrated into the system board, and does not require individual cables to each
NVDIMM-N that is typical of Super Cap based solutions.
On first detection of an power loss, the server activates the battery and triggers the NVDIMM-N to save its DRAM contents to
flash. The Save process takes approximately a minute to complete in the T640, R640, R740/R740XD, R840, R940 and R940xa
servers and 140 seconds to complete in the MX740c and MX840c servers. During this time the battery is required to provide
power for backup. The battery supplies power only to server sub-systems that must be powered for the save to complete. All
other subsystems are powered down or placed into a low power state to conserve battery life. After the save completes, the
battery is deactivated, and the server is allowed to power down completely. In modular chassis, the batteries also provide power
to the system fans to provide cooling during the NVDIMM save after an power loss event.
Table 6. Battery LED Behavior
Battery Operation Green LED
Powered Off Off
Idle (not charging and not enabled while the server is on) Off
Maintenance Charging On
Critical Charging (battery capacity is below minimum required for NVDIMM-N Save, server is
powered on)
Blinking
Battery Enabled and Discharging (Power loss detected, Battery supplying power for NVDIMM-
N Save operation)
Blinking
If a battery is not installed or not fully charged, BIOS will restore the NVDIMM-N DRAM contents from its onboard flash, but
BIOS will keep the NVDIMM-N in Read-Only mode. This allows OS and applications to have access to NVDIMM-N data, and at
the same time protect the NVDIMM-N from potential data loss due to power loss.
The NVDIMM-N battery is not hot swappable. To prevent data loss and potential damage to your system, ensure that the
system, LEDs on the system, LEDs on NVDIMM-N, and LEDs on NVDIMM-N battery are turned off before installing or removing
the NVDIMM-N Battery.
Figure 7 below shows the system board connections for the NVDIMM-N Battery cables in the R740/R740XD (Items 36 and 38).
Figure 8 shows how to install and mount the battery in the R740/R740XD. Please refer to each server’s Installation and Service
Manual for detailed instructions on how to install or remove the battery.
Hardware
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