44 lines
1.7 KiB
Markdown
44 lines
1.7 KiB
Markdown
---
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title: "MPPT"
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date: 2025-01-27
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draft: false
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description: "a description"
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tags: ["MPPT", "solar"]
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---
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# MPPT Module
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If the system is powered by solar, a dedicated MPPT (Maximum Power Point Tracking) module can be added. It tries to track the best current and voltage, so that the battery gets maximized charging current.
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The currently used MPPT module is based on the CN3795 and limits max current to 2.4A.
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<!-- TODO: Add photo of the new modular MPPT board -->
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The module has two configurable values: **Input Power Point (MPPT)** and **Output Voltage (Battery Charge Voltage)**. These are set using fixed resistors rather than potentiometers to ensure stability and reduce costs.
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### Configuration
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The voltages are determined by voltage dividers. The default values are:
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- **MPPT Voltage:** ~17.1V (set by R2 and R5)
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- **Battery Voltage:** ~14.7V (set by R8 and R1)
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#### Formulas
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The reference voltage for the CN3795 is 1.205V.
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- $V_{MPPT} = 1.205 \times (1 + \frac{R2}{R5})$
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- $V_{BAT} = 1.205 \times (1 + \frac{R8}{R1})$
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Default resistor values:
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- $R1, R5 = 2.491k\Omega$
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- $R2 = 33k\Omega$
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- $R8 = 27k\Omega$
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### Status LEDs
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- **D4 (Red):** Charging
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- **D5 (Green):** Done / Standby
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#Setup
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{{< alert >}}
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Note: Only protected Batteries are supported!
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{{< /alert >}}
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1. **Verify Resistors:** Before connecting, ensure that R2 and R8 match your solar panel's MPPT voltage and your battery's required charging voltage.
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2. **Initial Test:** Supply the Ext Charge connector with a voltage higher than the MPPT setpoint (e.g., 20V) and a limited current (suggested 100mA).
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3. **Check Output:** Measure the output voltage at the battery connector. It should match the calculated $V_{BAT}$.
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4. **Connect Battery:** Once verified, you can connect the battery and the solar panel.
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