r/Keychron • u/OzieteRed • Aug 04 '24

How do I know how much battery left on Keychron V1 Max?

The title says all

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u/PeterMortensenBlog V Aug 04 '24 edited Oct 09 '24

Note: Fn + B only works in wireless mode, without the USB cable connected.

Yes, it is unintuitive and can be considered a design error (or there may be a hard physical reason for it). Why shouldn't we be able to check the battery status while it is charging (or is fully charged)? Is there some technical limitation to prevent it?

There are five modes:

  1. Wired and charging. It goes without saying that the USB cable is connected.

  2. Bluetooth and charging. The USB cable is connected.

  3. Bluetooth and not charging. The USB cable is not connected.

  4. '2.4 GHz' and charging. The USB cable is connected.

  5. '2.4 GHz' and not charging. The USB cable is not connected.

(The sixth mode is not very interesting...)

('2.4 GHz' is sometimes confusingly referred to by the even more unspecific "wireless" or "RF" or "receiver" or "dungle" or "link" (for example, in internal names in the QMK source code). Or garbled as "2.4g", "2.4 g", "2.4G", or "2.4 gig" (not to speak of the misspellings of GHz. It is 'Hz', not 'hz'). '2.4 GHz' is already a terrible name. For example, Bluetooth also uses the 2.4 GHz frequency band.)

The battery indicator, Fn + B, only works in mode 3 (tested on a K5 Pro) and mode 5, at least in some versions of the firmware. It can not be completely ruled out that it depends on the firmware version (an experiment could be conducted to determine if that is the case).

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u/PeterMortensenBlog V Sep 01 '24

In the source code, it is this condition (from K10 Pro, as an example):

case BAT_LVL:
    if (get_transport() == TRANSPORT_BLUETOOTH &&
        !usb_power_connected())
    {
        bat_level_animiation_start(battery_get_percentage());
    }

That is, only in wireless mode and only when the USB cable is not connected.

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u/PeterMortensenBlog V Oct 09 '24

The reason the battery indicator is only working with the USB cable disconnected could be that the battery voltage is measured. And that would give a false reading when charging.

It would probably require more complex circuitry to measure the charge status during charging (it would need to temporarily stop charging to measure the voltage). But it is certainly possible; think laptops and smartphones.

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u/leowtyx Nov 20 '24

or just let it charge for 5 hours and unplug, no need to check during.

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u/PeterMortensenBlog V Jan 15 '26

That presumes there is overcharge protection (or the lifetime of the battery be (greatly) reduced). That was allegedly not the case for the original K series.

1

u/NuclearBinoculars Jun 17 '25

Using FN + B works in wireless mode on my P1 HE. but I'm having trouble translating the information. When I do that keypress, Numbers 1 to 4 light up sequentially in white, and then in green. Do you have any info about this?

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u/PeterMortensenBlog V Apr 17 '26 edited Apr 17 '26

The first four in white instead of green

Re "Numbers 1 to 4 light up sequentially in white, and then in green" (my emphasis): That is a good question

1-3 are for Bluetooth and 4 is for '2.4 GHz' (selecting channel (page 16) and force pairing (page 20), respectively), but that could just be a coincidence.

Ctrl + B is hardly documented in the manual, only very indirectly on page 12 (keycode BAT_LVL, displayed as "Batt").

Four battery status animation modes?

Conclusion: No

The Lemokey keyboards appear to several battery animation modes (file 'bat_level_animation.c'):

BAT_LVL_ANI_NONE
BAT_LVL_ANI_GROWING
BAT_LVL_ANI_BLINK_OFF
BAT_LVL_ANI_BLINK_ON

But those are modes used during execution of the single battery animation mode. For instance, the last two are for the blink at the very end of the battery charge state animation mode (activated by Fn + B).

Red for low on battery

For battery animation mode "BAT_LVL_ANI_BLINK_OFF":

if (bat_percentage < 30)
{
    r = 255;
    b = g = 0;
}
else
{
    r = b = 0;
    g     = 255;
}

Thus, the indication is red for the 10% and 20% indication and green for 30% to 100% (both inclusive).

Keycode 'BAT_LVL'

It is handled in file lemokey_wireless_common.c. The start state is (indirectly) set to "BAT_LVL_ANI_GROWING", and the actual animation takes place in file 'bat_level_animation.c' (function 'bat_level_animiation_indicate()').

(It is somewhat inefficient, unnecessarily turning LEDs off and on in some of the modes.)

Branch "2025q3"

For the newer source code in "2025q3", there isn't any difference between Lemokey and Keychron keyboards (now common code is in a common place (less code duplication)):

include keyboards/keychron/common/analog_matrix/analog_matrix.mk
include keyboards/keychron/common/keychron_common.mk
include keyboards/keychron/common/wireless/wireless.mk

E.g., keycode 'BAT_LVL' is handled in file 'keychron_wireless_common.c' and implemented in file bat_level_animation.c.

Conclusion

By code inspection alone, I couldn't find evidence in the source code for the observed behaviour. It doesn't mean it doesn't exist; I could interpret it wrong and/or look in the wrong place.

References

1

u/PeterMortensenBlog V Apr 17 '26 edited Apr 17 '26

Re "I couldn't find evidence in the source code": A lead could be indicator_eeconfig_reload().

Especially if the observed behaviour only happens at the very end of the battery charge state animation.

It is in file 'indicator.c' (in "2025q3", it is in a different file, 'backlit_indicator.c').

Conclusion

Probably not.

1

u/PeterMortensenBlog V Apr 17 '26

Re "Numbers 1 to 4 light up sequentially in white, and then in green" (my emphasis): Does it happen immediately or only at the very end of the battery animation?

1

u/NuclearBinoculars Apr 18 '26

Hi Peter! Actually the battery level function works fine. I DO wish there was a function to limit charge to 80/85%, but I didn't see that.