I actually had a similar problem with my headset, and it turns out that
a headset can report its battery status through Apple-specific AT
commands, namely through a "AT+IPHONEACCEV command". If you listen
through Wireshark or something similar, you may periodically receive
battery level info. In my case it was "AT+IPHONEACCEV=2,1,2,2,0", which
corresponded to 30% of battery (value after "1" means "battery level",
and level is scaled between 0 and 9). Hope that helps.

Documentation:
https://developer.apple.com/accessories/Accessory-Design-Guidelines.pdf

W dniu 23.01.2019 o 18:27, Grigory Fateyev pisze:> It has such info:
>
> [MDR-XB650BT]# info 00:18:09:C5:44:1E
> Device 00:18:09:C5:44:1E
> Name: MDR-XB650BT
> Alias: MDR-XB650BT
> Class: 0x240404
> Icon: audio-card
> Paired: yes
> Trusted: yes
> Blocked: no
> Connected: yes
> LegacyPairing: no
> UUID: Headset                   (00001108-0000-1000-8000-00805f9b34fb)
> UUID: Audio Sink                (0000110b-0000-1000-8000-00805f9b34fb)
> UUID: A/V Remote Control Target (0000110c-0000-1000-8000-00805f9b34fb)
> UUID: A/V Remote Control        (0000110e-0000-1000-8000-00805f9b34fb)
> UUID: Handsfree                 (0000111e-0000-1000-8000-00805f9b34fb)
>
> PS. Luiz, sorry for the direct copy!
>
> =D1=81=D1=80, 23 =D1=8F=D0=BD=D0=B2. 2019 =D0=B3. =D0=B2 20:04, Luiz
August=
> o von Dentz <luiz.dentz@gmail.com>:
>>
>> Hi Grigory,
>> On Wed, Jan 23, 2019 at 6:22 PM Grigory Fateyev <gfborn@gmail.com> wrote:
>>>
>>> Hello!
>>>
>>> I have a bluetooth headset Sony MDR-XB650BT.
>>>
>>> # hcitool info 00:18:09:C5:44:1E
>>> Requesting information ...
>>> BD Address:  00:18:09:C5:44:1E
>>> OUI Company: CRESYN (00-18-09)
>>> Device Name: MDR-XB650BT
>>> LMP Version: 4.0 (0x6) LMP Subversion: 0x2576
>>> Manufacturer: Cambridge Silicon Radio (10)
>>> Features page 0: 0xff 0xff 0x8f 0xfe 0x9b 0xff 0x59 0x87
>>> <3-slot packets> <5-slot packets> <encryption> <slot offset>
>>> <timing accuracy> <role switch> <hold mode> <sniff mode>
>>> <park state> <RSSI> <channel quality> <SCO link> <HV2 packets>
>>> <HV3 packets> <u-law log> <A-law log> <CVSD> <paging scheme>
>>> <power control> <transparent SCO> <broadcast encrypt>
>>> <EDR ACL 2 Mbps> <EDR ACL 3 Mbps> <enhanced iscan>
>>> <interlaced iscan> <interlaced pscan> <inquiry with RSSI>
>>> <extended SCO> <EV4 packets> <EV5 packets> <AFH cap. slave>
>>> <AFH class. slave> <3-slot EDR ACL> <5-slot EDR ACL>
>>> <sniff subrating> <pause encryption> <AFH cap. master>
>>> <AFH class. master> <EDR eSCO 2 Mbps> <EDR eSCO 3 Mbps>
>>> <3-slot EDR eSCO> <extended inquiry> <simple pairing>
>>> <encapsulated PDU> <non-flush flag> <LSTO> <inquiry TX power>
>>> <EPC> <extended features>
>>> Features page 1: 0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x00
>>>
>>> I'd like to get the energy level at least in shell. In which direction
>>> I should look for? How to know if my device has GATT support? If it
>>> connected with Android smartphone, where Android version is < 6.0, it
>>> has an icon with level in percents. I want to get the same on my linux
>>> machine.
>>
>> bluetoothd should be able to detect if there is a battery service,
>> well at least if you are connect over LE, note that in past there
>> exists ways to fetch the battery level of AVRCP and HFP via AT
>> commands, so perhaps Android is using one of those, btw you should be
>> able to see what bluetoothd has discover with:
>>
>> bluetoothctl> info <bdaddr>
>>
>>> Thank you!
>>>
>>> --
>>> Grigory
>>
>>
>>
>> --
>> Luiz Augusto von Dentz
>
>
>
> --=20
> Grigory
>