Hey everyone, I'm diving into setting up a DIY photovoltaic (PV) system and I've got some questions about Maximum Power Point Tracking (MPPT). I'm picking up four 100W solar panels (with a maximum power point of 2.9A at 34.5V) and using an EG8010 inverter module, which seems pretty straightforward since it includes the necessary components and even a wiring schematic. I'll be using a salvaged 12V lead-acid battery for backup, primarily for use at dusk and dawn when the panels aren't producing enough energy. I've been reading about MPPT battery chargers and I get that they optimize the power output, but I'm confused about how the different charging modes like bulk, absorption, and float fit into this. It seems like these chargers adapt to the battery's needs rather than focusing on the solar panels' output. Am I missing something here? What are the algorithms and hardware behind achieving MPPT? I'm also curious why the inverter isn't fed directly from the solar panels, since that could minimize energy loss compared to the low-voltage DC output of a battery. Looking forward to your insights!
3 Answers
Great question! MPPT chargers are designed to extract the maximum power from your solar panels by adjusting the electrical operating point. The idea is that they pull in current at the highest voltage of the panels using a DC/DC converter while adjusting the output voltage to charge your battery efficiently. Basically, they manage the voltage and current changes that occur with varying sunlight conditions to remain at the peak operating point of the solar panels while safely charging your battery. As for connecting the inverter directly to the panels, it’s a good strategy when there’s plenty of sunlight. However, you want to make sure your batteries aren't depleted at night, so charge controllers prevent them from discharging into the panels when it's dark, which is why they usually connect to batteries instead.
To address your concern about connecting the inverter directly to the panels: While it can reduce cable losses, it also complicates things because if the panels were supplying too much power overnight, the batteries could drain back into the panels unless you use a relay or advanced controller to manage that flow. Your idea of a relay to switch the inverter between the solar panel and battery is handy! Just ensure your system is set up safely to avoid damage to your components.
Thanks! I’ll keep that in mind—I'm excited to experiment with this setup.
You’ve got the right idea! The key difference with MPPT is that it extracts energy from solar panels at their maximum voltage and current. If you used a PWM (Pulse Width Modulation) charger instead, it might reduce efficiency by charging at lower voltages, especially with high voltage panels where you could lose a significant amount of power. With panels, you’re aiming to make the most of their output, and that’s where MPPT shines, especially if your battery voltage is lower.
That makes sense, thanks for the clarification! It sounds like MPPT really maximizes efficiency, especially in fluctuating conditions.