在linux os中，使用4.00.11_Linux_MegaCLI查询BBU电池信息，发现Max Error: 100%
而不是正常的2%。此时并不一定代表电池故障，这有可能是电池一个正常的调整过程。
Max error的含义：
Max error是一个衡量标准，用来比较电量读取精确度。当一个电池正常的relearn周期完成时，会设置Max error为2%。 每比较一次，如果发现比较结果错误，MAX error值变大。当数值达到10%时，Firmware会把MAX error自动变为100%，同时强制设置为Write-Through模式。
此时，一个新的relearn周期会启动，当relearn周期正常完成后，会把MAX error 设置为2%，同时切换回Write-Back模式。
Relearn的含义：
Relearn 包括电池的放电和充电两个过程。一般来说, Firmware 会每隔30天启动一次relearn流程。同时，fw 切换 WB模式为 WT模式，直到relearn完成再切回去（一般是完成充电电量的60%或是70%左右）。整个relearn包括以下几个动作: relearn start, WB to WT, change pending, relearn finished, and change from WT to WB等.
注意：对于一些老的fw, 如果客户默认设置为WB模式, 当relearn开始时，WB有可能不会切换到WT模式。
判断一个BBU电池是否需要更换，可以看“Battery Replacement required ”参数，如果是“YES”，则表示需要更换了
[root@ tmp]# /opt/MegaRAID/MegaCli/MegaCli64 -adpbbucmd -aALL BBU status for Adapter: 0 BatteryType: iBBU Voltage: 4017 mV Current: 0 mA Temperature: 20 C BBU Firmware Status: Charging Status : None Voltage : OK Temperature : OK Learn Cycle Requested : No Learn Cycle Active : No Learn Cycle Status : OK Learn Cycle Timeout : No I2c Errors Detected : No Battery Pack Missing : No Battery Replacement required : No Remaining Capacity Low : No Periodic Learn Required : No Battery state: GasGuageStatus: Fully Discharged : No Fully Charged : Yes Discharging : Yes Initialized : Yes Remaining Time Alarm : No Remaining Capacity Alarm: No Discharge Terminated : No Over Temperature : No Charging Terminated : No Over Charged : No Relative State of Charge: 98 % Charger System State: 49168 Charger System Ctrl: 0 Charging current: 0 mA Absolute state of charge: 93 % Max Error: 2 % BBU Capacity Info for Adapter: 0 Relative State of Charge: 98 % Absolute State of charge: 93 % Remaining Capacity: 1131 mAh Full Charge Capacity: 1149 mAh Run time to empty: 65535 Min Average time to empty: 65535 Min Average Time to full: 65535 Min Cycle Count: 2 Max Error: 2 % Remaining Capacity Alarm: 120 mAh Remaining Time Alarm: 10 Min BBU Design Info for Adapter: 0 Date of Manufacture: 04/15, 2010 Design Capacity: 1215 mAh Design Voltage: 3700 mV Specification Info: 33 Serial Number: 2005 Pack Stat Configuration: 0x64b0 Manufacture Name: LS1111001B Device Name: 3598301 Device Chemistry: LION Battery FRU: N/A BBU Properties for Adapter: 0 Auto Learn Period: 2592000 Sec Next Learn time: 356764081 Sec Learn Delay Interval:0 Hours Auto-Learn Mode: Enabled
原文地址：https://support.huawei.com/enterprise/zh/knowledge/EKB1001988104