B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 203; Flight Crew Type 4800
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Diverted; Flight Crew Landed As Precaution; General Maintenance Action
Aircraft
[In cruise flight] dual IRS DC Fail lights illuminated. Captain retained control and directed QRH. I read QRH. We follow QRH and checked for popped CBs. No popped CBs. Battery voltage low at 11 Volts. QRH advised to consider a divert to nearest suitable airport because Engine APU fire extinguishing might not be available if needed. APU might not start. Upon coordination with Dispatch and crew consultation; Captain elected to divert to [a nearby alternate]. I agreed with her decision and judgment. Upon divert request with ATC; we explained that we were diverting as a precaution for our electrical problem. We had no indication of any further systems degradation and did not declare an emergency. We also referred to our divert considerations on the standard checklist card. Captain advised crew and passengers of the situation. We flew a safe and uneventful arrival; approach; and landing. Upon taxi to [the] gate the APU; as QRH predicted; failed to start. At the gate we shut down the number 2 engine; connected ground power; and then shut down number 1 engine.
[Report narrative contained no additional information.]
B737 flight crew reported diverting to an alternate after both IRS DC fail lights illuminated in cruise.