The Victron MPPT 75/15 is a solar charge controller that maximizes energy harvest from solar panels using Maximum Power Point Tracking (MPPT) technology. It handles up to 75V input and delivers 15A charging current, efficiently converting excess voltage into usable current for 12V or 24V battery systems. Designed for off-grid setups like RVs and marine applications, it features Bluetooth monitoring, temperature compensation, and multi-stage charging to protect lithium-ion, AGM, or gel batteries.
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How does the MPPT 75/15 optimize solar charging?
The controller continuously adjusts its input resistance to extract the maximum power from solar panels, even under partial shading or temperature fluctuations. By converting excess voltage into current, it boosts charging efficiency by up to 30% compared to PWM controllers.
At its core, the MPPT algorithm samples panel voltage 40 times/second to lock onto the ideal power-voltage (P-V) curve. For example, a 100W panel at 30V/3.3A would normally waste energy in a 12V system. The 75/15 steps down the voltage to 14.4V, increasing current to 6.94A (100W ÷ 14.4V). Pro Tip: Pair panels with a Voc below 75V—exceeding this trips overvoltage protection. Transitional phases between bulk/absorption/float stages are managed by adaptive algorithms.
What solar panel configurations work with the 75/15?
The controller supports 12V/24V auto-detection and panels with max 75V open-circuit voltage. For 12V systems, panels should output 18–75V; for 24V, 36–75V. Series connections multiply voltage while parallel setups increase current.
Let’s break it down: A 12V system using two 20V panels in series gives 40V input—well within the 75V limit. This setup maintains performance even if one panel is shaded. However, three 30V panels in series (90V total) would exceed the controller’s threshold. Practically speaking, the 75/15’s 15A output caps solar input at ~220W for 12V (15A × 14.4V) or 440W for 24V systems. Pro Tip: Use Victron’s MPPT Calculator app to avoid undersizing panels.
| Configuration | 12V System | 24V System |
|---|---|---|
| Max Solar Power | 220W | 440W |
| Optimal Panel Voc | 18-50V | 36-75V |
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Can it charge lithium batteries safely?
Yes, the 75/15 supports LiFePO4 profiles with adjustable absorption/float voltages. It automatically detects battery voltage and applies temperature-compensated charging, crucial for lithium longevity.
The controller’s preset lithium mode uses a 14.2V absorption and 13.5V float for 12V systems—slightly below lead-acid settings to prevent plating. For custom setups, the VictronConnect app lets users fine-tune parameters like tail current and absorption duration. Imagine a 100Ah lithium bank: the 75/15’s 15A output delivers 0.15C charging, balancing speed and cell stress. Pro Tip: Enable “Storage Mode” if the system sits idle—it periodically tops up batteries to 13.2V (12V) to minimize degradation. Transitional algorithms ensure smooth shifts between charging phases without voltage overshoot.
What monitoring features does it offer?
Built-in Bluetooth connects to VictronConnect for real-time tracking of input voltage, battery SOC, and energy yields. Historical data logs reveal performance trends over days or weeks.
Through the app, users see metrics like daily harvested energy (kWh) and peak power (W). For instance, a camper might notice 1.2kW harvested on a sunny day versus 0.4kW when cloudy. The controller also reports faults—like overvoltage or reverse polarity—with timestamps. Pro Tip: Pair with a Victron SmartShunt for coulomb-counting accuracy within 0.1%. Beyond basic stats, the 75/15 syncs with Cerbo GX systems for centralized monitoring in marine/RV setups.
| Feature | 75/15 | PWM Controllers |
|---|---|---|
| Efficiency | 98% | 70-80% |
| Data Logging | Yes | No |
How does temperature affect performance?
The built-in temperature sensor adjusts charging voltages based on battery temperature, preventing overcharge in heat or undercharge in cold environments.
In a freezing RV at -10°C, the controller increases absorption voltage by 0.3V to overcome higher internal battery resistance. Conversely, in a 45°C engine room, it lowers voltage to reduce gassing. This compensation follows a -16mV/°C slope for lead-acid and -3mV/°C for lithium. Pro Tip: For remote battery banks, use the optional VBatTemp sensor—the controller’s internal sensor only measures ambient, not battery core temps. Transitional adjustments occur incrementally to avoid abrupt voltage changes that confuse battery management systems.
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FAQs
No—it’s designed for 12V/24V only. Use Victron’s SmartSolar 150/35 for 48V setups.
Can I parallel multiple 75/15 controllers?
Yes, for expanded capacity. Sync them via VE.Smart Networking to prevent voltage conflicts.
What’s the warranty period?
Victron offers a 5-year warranty, contingent on proper installation and operating temperatures below 45°C.
