1794- Slot 0 Drive Array Array accelator battery charge low

Hi,

I have HP Proliant ML 350 G5, recently change 2 new hard disk and made Rad 1+0  , after that I am geting 2 errors, 

1-  1794- Slot 0 Drive Array Array accelator battery charge low

2- 1720 - Slot 0 Driver Array - S.M.A.R.T. Hard ,Drive detect imminent failure , 

Screen Shot Attached 

Drive error cause of Batter low ?

Kindly respond.

Many Thanks,

Jemshid