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update: improve documentation and restructure code for modular hardware integration, add CAN communication to HAL, and update KiCad layouts

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2026-01-23 22:02:14 +01:00
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website/content/Hardware/1737993469847-MPPT/index.md
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@@ -5,22 +5,39 @@ draft: false
description: "a description"
tags: ["MPPT", "solar"]
---
# MPPT
If the board is powered by solar, a on board MPPT converter tries to track the best current and voltage, so that the battery gets maximized charging current.
# MPPT Module
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.
The currently used MPPT limits max current to 2A.
The currently used MPPT module is based on the CN3795 and limits max current to 2.4A.
There are two adjustable values for the MPPT, Input Power Point and Output Voltage.
<!-- TODO: Add photo of the new modular MPPT board -->
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.
### Configuration
The voltages are determined by voltage dividers. The default values are:
- **MPPT Voltage:** ~17.1V (set by R2 and R5)
- **Battery Voltage:** ~14.7V (set by R8 and R1)
#### Formulas
The reference voltage for the CN3795 is 1.205V.
- $V_{MPPT} = 1.205 \times (1 + \frac{R2}{R5})$
- $V_{BAT} = 1.205 \times (1 + \frac{R8}{R1})$
Default resistor values:
- $R1, R5 = 2.491k\Omega$
- $R2 = 33k\Omega$
- $R8 = 27k\Omega$
### Status LEDs
- **D4 (Red):** Charging
- **D5 (Green):** Done / Standby
#Setup
{{< alert >}}
Note: Only protected Batteries are supported!
{{< /alert >}}
1. Supply the Ext Charge connector with 20V and a limited current (suggested 100mA).
2. If the board does not startup, adjust the MPPT untill it supplies a output voltage. Note: The ESP should be able to startup at any settable output voltage, as it uses a converter to 3.3v anyways.
3. Adjust the Output Voltage to the correct charging voltage for your Chosen Battery.
4. Connect a sink (or the a non fully charged battery) to the Output, now adjust the MPPT so, that the Input Voltage drops to the optimal working Voltage of your Solar panel. The Converter will try to always keep the Panel at this Voltage by adjusting the Output Current accordingly.
Setting the MPPT slightly lower than the suggested Voltage will ensure more reliable operation, as the optimal voltage might drop a bit due to ageing and dust on the panel. Normally during summer there is more than enough power, so a slight inefficentcy won't be noticable.
However during winter in low light and bad weather conditions, that might be the difference between charging at all or no power. (If the panel does not reach the MPPT voltage, there is no charging current)
1. **Verify Resistors:** Before connecting, ensure that R2 and R8 match your solar panel's MPPT voltage and your battery's required charging voltage.
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).
3. **Check Output:** Measure the output voltage at the battery connector. It should match the calculated $V_{BAT}$.
4. **Connect Battery:** Once verified, you can connect the battery and the solar panel.