Hitachi G400 Hardware Reference Manual page 74

The warning indication disappears within six hours. Even when the warning is
shown, normal operation is assured in Write-Through. Read and write
performance is lowered because the Write Cache function is disabled.
If the storage system is not charged for more than six months, the battery
can become overcharged and sustain unrecoverable damage. To avoid this
situation, charge the battery more than 3 hours every six months.
Insulation performance
Insulation withstand voltage
Insulation resistance
74
Hitachi Virtual Storage Platform G400, G600 Hardware Reference Guide
Item
Mechanical specifications for VSP G400, G600
Specification
AC 1,500 V (100 mA, 1 min)
DC 500 V, 10 M Ω or more