2.9.3 Internal Battery Feature 2.9.5 Cooling 2.9.4 Power estimation tool Note:  Customer power sources should always maintain redundancy across BPA pairs; that  is, one power source or distribution panel supplies power for BPA1 and the separate power  source or distribution panel supplies power for BPA2.  As a best practice, connect the odd-numbered BPAs (BPA1 and BPA3) to one power  source or distribution panel, and the even-numbered PDUs (BPA2 and BPA4) to a separate  power source or distribution panel.  The Internal Battery Feature (IBF) is an option on the z15 server. It is shown in Figure 2-31 on  page 79 for air-cooled (RCA) or water-cooled (WCA) systems. The IBF provides a local  uninterrupted power source. The IBF further enhances the robustness of the power design, which increases power line  disturbance immunity. It provides battery power to preserve processor data during a loss of  power on all power feeds from the computer room. The IBF can hold power briefly during a  brownout, or for orderly shutdown for a longer outage. For information about the hold times,  which depend on the I/O configuration and amount of CPC drawers, see Chapter 11,  “Environmentals” on page 451. The power estimation tool for the z15 server allows you to enter your precise server  configuration to obtain an  estimate  of power consumption. Log in to the Resource link with  your user ID. Click  Planning  Tools  Power Estimation Tools . Specify the quantity for  the features that are installed in your system.  This tool estimates the power consumption for the specified configuration. The tool does  not verify that the specified configuration can be physically built. Tip:  The exact power consumption for your system varies. The object of the tool is to  estimate the power requirements to aid you in planning for your system installation. Actual  power consumption after installation can be confirmed by using the HMC Monitors  Dashboard task. The PU SCMs are cooled by a cold plate that is connected to the internal water-cooling loop.  The SC SCMs are air-cooled. In an air-cooled system, the radiator unit dissipates the heat  from the internal water loop with air. The radiator unit provides improved availability with N+ 2  pumps and blowers. The WCUs are fully redundant in an N+1 arrangement for both the  A-frame and the B-frame when present. 80  IBM z15 (8561) Technical Guide The following components plug into the BPAs X 2 for redundancy: GLYPH<SM590000> CPC Drawers, I/O Drawers, Switches, Radiators, WCUs, and Support Elements GLYPH<SM590000> The redundancy for each component plugs into the paired BPAs For example, for the top Support Element 1, one power supply plugs into BPA1 and the  second power supply plugs into the paired BPA2 for redundancy.