Unusual Battery Drain Problem on my Macbook Air mid 2013 13″

Since a few weeks I notice an unusual battery drain problem with my macbook air. I checked the battery health using coconut battery and I was sure my battery is going down the final destination path. But as a techy you cannot sit there an do nothing. Wo I started analyzing. Are there  some programs not entering sleep mode, do I have background processing updates running, are my energy saving options set right. Everything I checked was fine. After having checked all this I started to narrow down the changes of the last few weeks, and voila I found a change. I have bought a SD Card for the Air for storage extension, one of the cards which go seamless with the enclosure. By using the

pmset -g

command and a grep to the syslog

syslog | grep -i "Wake reason"

I found out that the „EHCI“ recently woke up the system every few minutes:


Aug 25 17:50:21 wall-e kernel[0] : Wake reason: EC.LidOpen EHC1 (User)
Aug 25 19:08:17 wall-e kernel[0] : Wake reason: EC.LidOpen (User)
Aug 25 21:06:12 wall-e kernel[0] : Wake reason: EC.LidOpen (User)
Aug 26 06:57:42 wall-e kernel[0] : Wake reason: EHC1
Aug 26 07:46:40 wall-e kernel[0] : Wake reason: EC.LidOpen (User)
Aug 26 07:55:47 wall-e kernel[0] : Wake reason: EC.DarkPME (Maintenance)
Aug 26 08:40:32 wall-e kernel[0] : Wake reason: EHC1
Aug 26 09:03:13 wall-e kernel[0] : Wake reason: EHC1
Aug 26 09:20:57 wall-e kernel[0] : Wake reason: EHC1
Aug 26 09:30:29 wall-e kernel[0] : Wake reason: EC.ACAttach EHC1 (Maintenance)
Aug 26 17:48:04 wall-e kernel[0] : Wake reason: EC.SleepTimer (SleepTimer)
Aug 27 07:41:03 wall-e kernel[0] : Wake reason: EC.DarkPME (Maintenance)
Aug 27 08:23:42 wall-e kernel[0] : Wake reason: EHC1
Aug 27 10:43:23 wall-e kernel[0] : Wake reason: EHC1
Aug 27 11:03:35 wall-e kernel[0] : Wake reason: EHC1
Aug 27 11:59:18 wall-e kernel[0] : Wake reason: EHC1
Aug 27 12:18:38 wall-e kernel[0] : Wake reason: EHC1
Aug 27 17:35:00 wall-e kernel[0] : Wake reason: EC.LidOpen EHC1 (User)
Aug 27 18:49:01 wall-e kernel[0] : Wake reason: EC.SleepTimer (SleepTimer)
Aug 28 07:55:30 wall-e kernel[0] : Wake reason: EC.DarkPME (Maintenance)
Aug 28 08:01:18 wall-e kernel[0] : Wake reason: EHC1
Aug 28 08:29:38 wall-e kernel[0] : Wake reason: EHC1
Aug 28 08:44:55 wall-e kernel[0] : Wake reason: EHC1
Aug 28 10:05:49 wall-e kernel[0] : Wake reason: EHC1
Aug 28 11:36:22 wall-e kernel[0] : Wake reason: EHC1
Aug 28 11:42:40 wall-e kernel[0] : Wake reason: EHC1

This fact is the reason for the battery drain during lid closed situation, because the EHCI = SDCARD USB Controller woke up the whole system. Therefore you get about 2% battery loss per hour and more. In my case closing the lid on friday afternoon at 100% and reopening on sunday noon with 63% left what is a very unusual situation for an apple user.

So what can you do. You can use programs like sleepwatcher to unmount the card when the system is going to sleep and remount if you for example open the lid. You can remove the card on a regular base. You also have to bear in mind that the sd card also draws juice during your normal work session so if you do not rely 100% on the card being mounted all the time, just remove it if you want to avoid the above described battery loss.

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