Querying battery status on a StorEdge 3510 FC

I have a StorEdge 3510 FC Rev 1102 with poor write performance. I suspect that the backup batteries are expired so I am issuing "show battery-status" from the sccli> prompt. It returns with "this operation is only supported on RAID primary controllers". When I issue "show configuration" it shows four FRUs, including it's two power supplies and the chassis, but not the batteries. There are no alerts in the syslog but that may be because ssagent is not running. I'd like to confirm that its designed to disable the write-back cache when both batteries are expired?  So, how can I