<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>

CC BY-SA 3.0
2015-09-05T19:10:15.330Z
But Lego battery pack has 7.4v 2200mAh, is almost the same with 6 nihm batteries
Sebastian Backis
CC BY-SA 3.0
2015-09-06T00:18:04.447Z
There is actually a wide variation among NiMH batteries. See http://www.philohome.com/batteries/bat.htm for some LEGO related battery comparisons.
David Lechner
CC BY-SA 3.0
2015-09-05T14:23:23.933Z
2015-09-06T00:11:38.807Z
2015-09-06T00:11:38.807Z
David Lechner
<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>

CC BY-SA 3.0
2015-09-05T14:24:53.683Z
Also see http://bricks.stackexchange.com/q/6456/3498
David Lechner
<ev3><battery>
EV3 with NiMH batteries
Sebastian Backis
# 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  

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## 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 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.  

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