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The title says it all. I am trying to troubleshoot a problem with the battery in a BBU RAID cache. During POST, an error is given something to the effect that the battery is low, the RAID cache is temporarily disabled and will begin working once the battery recharges. The battery is a 3.6v Ni-HM rechargeable battery, but when I take it out and measure its voltage, it is around 5v, no load. Originally, I assumed that this was because it was not under load, but as it turns out it reads the same voltage when I power on the server. This is very confusing to me, that a dead battery would have a higher voltage than it is supposed to.

I only run the server for around 6 hours each day. Is it possible that the battery discharges over night?

As a side note, I have tried connecting a pack of two AA batteries in place of the 'official' battery, but still don't have any luck. (By the way... If you ever do that, don't use alkaline batteries. They explode. You have to use rechargeable batteries. I speak from experience.)

I really need the extra performance boost of the cache, and so am willing to run the server 24/7 to keep the battery charged, but I don't want to if I don't have to.

For Clarification, my server is an HP Proliant ML350, with an HP Smart Array E200i RAID controller.

  • Knowing the make/model of the controller would surely be helpful. – joeqwerty Jan 18 '17 at 19:16
  • I wonder if the cache enables itself shortly thereafter once the RAID card convinces itself the battery is fine. – David Schwartz Jan 18 '17 at 19:21
  • No, because there is obviously a performance problem with the server... I am talking like 10mbps read speeds. – Kernel Stearns Jan 18 '17 at 19:24
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The battery recharge through the power provided by the PCI-express slot which, when the server is powered down, has only access to a very limited power source.

So, the battery should not recharge when the server is off.

Rather than trying other battery, get a compatible one and check if the error message disappear.

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  • Sorry, maybe I didn't clarify enough, but the RAID controller is built into the server, it is not a PCI-express slot add-on board. Therefore, the BBU connects directly to the motherboard. I would consider getting another battery, but I don't want to order anything until I know it will solve the problem. – Kernel Stearns Jan 18 '17 at 19:44
  • It's the same thing: when powered off, the motherboard have access to stand-by power only, which is very low. A battery should be quite cheap; I would not risk data integrity for little cost. If instead data integrity is not a priority, you can force write back operation even with a missing or dead battery. – shodanshok Jan 18 '17 at 20:29
  • I don't care about data integrity; if the power goes off, I lose my data anyway. Would you explain how to force write back operation with a missing battery? I have searched online and have not been able to find exactly how to do it on this model. – Kernel Stearns Jan 18 '17 at 20:35
  • Also, to clarify, if I only run the server for 6 hours each day, will the battery discharge enough over the other 18 hours to create the "battery failed" error? There is no point in replacing the battery if it just isn't having enough time to charge. – Kernel Stearns Jan 18 '17 at 20:39
  • The battery is apparently out of spec, and the performance need for battery backed cache is already established. Why do you not get a replacement? At worst you now have a spare, which will at some point be needed. – John Mahowald Jan 19 '17 at 3:23

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