---
title: Why does RubiQ think my fully-charged battery is dead?
description: RubiQ, Voltage Divider, Battery Issues, Wrong Cell Count, Calibration, INAV Configurator, Voltage Scale, Dead Battery Error, 4S vs 3S
---

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# Why does RubiQ think my fully-charged battery is dead?

## Diagnosing and Fixing Voltage Divider Issues

If you plug a fully charged 3-cell (3S) battery into your RubiQ, but the drone starts beeping and reporting a "Low Battery" or identifies it as a dead 4-cell (4S) battery, your voltage sensor likely needs calibration.

This guide will walk you through calculating the correct **Voltage Scale** to ensure your RubiQ reads the battery level accurately.

#### The Problem

Sometimes, the RubiQ flight controller reads a voltage that is slightly higher than reality.

- **Example:** A charged 3-cell battery has about **12.6 Volts**. If the RubiQ reads this as **13.5 Volts**, the computer gets confused. It assumes you must have plugged in a **4-cell battery** (which usually operates around 14–16V) but that the battery is dangerously dead.

To fix this, we simply need to tell the RubiQ Configurator to adjust how it "counts" the voltage.

#### What You Need

- Your RubiQ Drone
- A LiPo Battery (3S)
- A **Cell Checker** or Multimeter
- A computer with the **RubiQ Configurator** installed
- Micro USB cable

#### Step-by-Step Calibration Guide

### 1. Measure the Real Voltage

Before connecting to the computer, plug your battery into a **Cell Checker** (or measure with a multimeter). Write down the **Total Voltage** displayed on the screen (e.g., 12.5V).

### 2. Connect to Configurator

Plug the battery into the RubiQ, then plug the RubiQ into your computer via USB. Open the **RubiQ Configurator** and click **Connect**.

### 3. Find the "Reported" Voltage

Navigate to the **Configuration** tab. Look at the top of the screen (or the info section on the right). Note the voltage the RubiQ thinks it is receiving (e.g., 13.8V) as well as the number of cells it is detecting in the battery.

![Screenshot 2025-12-17 093413](https://support.edventures.com/hs-fs/hubfs/Knowledge_Base/Screenshot%202025-12-17%20093413.png?width=670&height=355&name=Screenshot%202025-12-17%20093413.png)

### 4. Calculate the New Scale

If the Real Voltage (Step 1) and Reported Voltage (Step 3) are different by more than 10%, or the info section is showing anything other than 3 cells (for a 3 cell battery), you need to change the **Voltage Scale** setting in the Configuration tab.

Use the following formula to find your new number:

**![Screenshot 2025-12-17 094958](https://support.edventures.com/hs-fs/hubfs/Knowledge_Base/Screenshot%202025-12-17%20094958.png?width=549&height=70&name=Screenshot%202025-12-17%20094958.png)**

**Example Calculation:**

- **Actual Voltage** (Cell Checker): 12.6V
- **Reported Voltage** (Configurator): 13.8V
- **Old Voltage Scale** (Default): 1100
- (12.6 / 13.8) x 1100 = **1004**

### 5. Save and Finish

Type your new number into the **Voltage Scale** box and click **Save and Reboot**. Once the drone reboots, check the top of the screen to ensure the voltage now matches your cell checker.

![Screenshot 2025-12-17 093430](https://support.edventures.com/hs-fs/hubfs/Knowledge_Base/Screenshot%202025-12-17%20093430.png?width=670&height=356&name=Screenshot%202025-12-17%20093430.png)

#### Important: Check Cell Voltage Settings

While you are in the Configuration tab, please verify that your **Minimum Cell Voltage** and **Maximum Cell Voltage** settings match the defaults for a standard LiPo battery.

- **Minimum Cell Voltage:** 3.3V
- **Maximum Cell Voltage:** 4.24V

If "Maximum Cell Voltage" is set too low (e.g., 4.0V), a fully charged battery will confuse the drone's cell counter.

 

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