Answers.Body: <p>EDIT:</p>
  
  <p>Yes, pressing the button will affect the indicator and low battery alarm/shutdown.</p>
  
  <p>From the official LEGO firmware:</p>
  
  <pre><code>#define   BATT_INDICATOR_HIGH           7500          //!&lt; Battery indicator high [mV]
  #define   BATT_INDICATOR_LOW            6200          //!&lt; Battery indicator low [mV]
  
  #define   ACCU_INDICATOR_HIGH           7500          //!&lt; Rechargeable battery indicator high [mV]
  #define   ACCU_INDICATOR_LOW            7100          //!&lt; Rechargeable battery indicator low [mV]
  
  ...
  
  #define   LOW_VOLTAGE_SHUTDOWN_TIME     10000         //!&lt; Time from shutdown lower limit to shutdown [mS]
  
  #define   BATT_WARNING_HIGH             6.2           //!&lt; Battery voltage warning upper limit [V]
  #define   BATT_WARNING_LOW              5.5           //!&lt; Battery voltage warning lower limit [V]
  #define   BATT_SHUTDOWN_HIGH            5.5           //!&lt; Battery voltage shutdown upper limit [V]
  #define   BATT_SHUTDOWN_LOW             4.5           //!&lt; Battery voltage shutdown lower limit [V]
  
  #define   ACCU_WARNING_HIGH             7.1           //!&lt; Rechargeable battery voltage warning upper limit [V]
  #define   ACCU_WARNING_LOW              6.5           //!&lt; Rechargeable battery voltage warning lower limit [V]
  #define   ACCU_SHUTDOWN_HIGH            6.5           //!&lt; Rechargeable battery voltage shutdown upper limit [V]
  #define   ACCU_SHUTDOWN_LOW             6.0           //!&lt; Rechargeable battery voltage shutdown lower limit [V]
  </code></pre>
  
  <p>The <code>BATT_*</code> are used when the button is not pressed and the the <code>ACCU_*</code> values are used when the button is pressed.</p>
  
  <p>ORIGINAL ANSWER:</p>
  
  <p>The small black circle is used by the <a href="http://shop.lego.com/en-US/EV3-Rechargeable-DC-Battery-45501" rel="nofollow">Li-ion battery pack</a> from LEGO. This battery pack actually operates at a higher voltage that Alkaline batteries. On the other hand, NiMH batteries operate at a lower voltage than Alkaline, so pressing the small black circle would have the opposite effect of what you are hoping that it will do.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-09-05T19:10:15.330Z
Answers.Text: But Lego battery pack has 7.4v 2200mAh, is almost the same with 6 nihm batteries
Answers.UserDisplayName: Sebastian Backis
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-09-06T00:18:04.447Z
Answers.Text: There is actually a wide variation among NiMH batteries. See http://www.philohome.com/batteries/bat.htm for some LEGO related battery comparisons.
Answers.UserDisplayName: David Lechner
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-09-05T14:23:23.933Z
Answers.LastActivityDate: 2015-09-06T00:11:38.807Z
Answers.LastEditDate: 2015-09-06T00:11:38.807Z
Answers.UserDisplayName: David Lechner
Body: <p>Could I use 6 NiMH 1.2V batteries and keep pressed the small black circle in the battery compartment in order to adjust the battery gauge and low battery alarm?</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-09-05T14:24:53.683Z
Comments.Text: Also see http://bricks.stackexchange.com/q/6456/3498
Comments.UserDisplayName: David Lechner
Tags: <ev3><battery>
Title: EV3 with NiMH batteries
UserDisplayName: Sebastian Backis
ThreadText: # EV3 with NiMH batteries
  
  (Asked by: username_0 on 2015-09-04)
  
  Could I use 6 NiMH 1.2V batteries and keep pressed the small black circle in the battery compartment in order to adjust the battery gauge and low battery alarm?
  
  **Tags:** ev3, battery
  
  > **Comments:**
  > **username_1**: Also see http://bricks.stackexchange.com/q/6456/3498  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2015-09-05. Score: 1 | Accepted answer
  
  EDIT:
  
  Yes, pressing the button will affect the indicator and low battery alarm/shutdown.
  
  From the official LEGO firmware:
  
  ```
  #define   BATT_INDICATOR_HIGH           7500          //!< Battery indicator high [mV]
  #define   BATT_INDICATOR_LOW            6200          //!< Battery indicator low [mV]
  
  #define   ACCU_INDICATOR_HIGH           7500          //!< Rechargeable battery indicator high [mV]
  #define   ACCU_INDICATOR_LOW            7100          //!< Rechargeable battery indicator low [mV]
  
  ...
  
  #define   LOW_VOLTAGE_SHUTDOWN_TIME     10000         //!< Time from shutdown lower limit to shutdown [mS]
  
  #define   BATT_WARNING_HIGH             6.2           //!< Battery voltage warning upper limit [V]
  #define   BATT_WARNING_LOW              5.5           //!< Battery voltage warning lower limit [V]
  #define   BATT_SHUTDOWN_HIGH            5.5           //!< Battery voltage shutdown upper limit [V]
  #define   BATT_SHUTDOWN_LOW             4.5           //!< Battery voltage shutdown lower limit [V]
  
  #define   ACCU_WARNING_HIGH             7.1           //!< Rechargeable battery voltage warning upper limit [V]
  #define   ACCU_WARNING_LOW              6.5           //!< Rechargeable battery voltage warning lower limit [V]
  #define   ACCU_SHUTDOWN_HIGH            6.5           //!< Rechargeable battery voltage shutdown upper limit [V]
  #define   ACCU_SHUTDOWN_LOW             6.0           //!< Rechargeable battery voltage shutdown lower limit [V]
  
  ```
  
  The `BATT_*` are used when the button is not pressed and the the `ACCU_*` values are used when the button is pressed.
  
  ORIGINAL ANSWER:
  
  The small black circle is used by the [Li-ion battery pack](http://shop.lego.com/en-US/EV3-Rechargeable-DC-Battery-45501) from LEGO. This battery pack actually operates at a higher voltage that Alkaline batteries. On the other hand, NiMH batteries operate at a lower voltage than Alkaline, so pressing the small black circle would have the opposite effect of what you are hoping that it will do.
  
  > **Comments:**
  > **username_0**: But Lego battery pack has 7.4v 2200mAh, is almost the same with 6 nihm batteries  
  > **username_1**: There is actually a wide variation among NiMH batteries. See http://www.philohome.com/batteries/bat.htm for some LEGO related battery comparisons.  
  
  ---
  
  