I have a Redarc BCDC 12V 40A charger and I'm wondering about how the float stage works with my setup. I'm charging two 12V 315 amp/hr batteries in parallel for a total of 630 amp/hr and have 400 watts of solar panels on the roof. Every morning, my Victron Smart Shunt shows about a 30 to 40 amp/hr drop from my battery bank. Typically, it reaches 100% charge by midday, but after that, it seems like the MPPT charger stops providing power. For instance, I hit 100% at around 11AM but by 4PM, I'm at -22 amp/hr even though it's still sunny. The only load is a 12V fridge, and I thought the solar could handle that. Is the MPPT just maintaining a certain voltage after a full charge, like 13.3V? I'm curious to know if it only charges once a day or if this behavior is normal to protect the batteries.
2 Answers
I think what you're seeing is pretty common. If your solar panels aren't tracking the sun, they might not be producing enough power as the day goes on. Once the solar input drops below what your loads are drawing, that's when you'll see negative current and your batteries start depleting. It might be worth checking your wattage output throughout the day to see how it correlates with your battery usage. Just be cautious during low sunlight times and consider disconnecting your batteries if you're drawing too much.
From my experience, if your lithium settings don't have a float stage, what’s happening is your charger is going into absorption mode until it senses a drop in battery charge, which sounds exactly like what you're experiencing. It’s designed to prevent overcharging. When your batteries hit around 99%, they might start charging again as needed. It's definitely working within safety parameters to protect your batteries, so it’s worth keeping an eye on voltage during those sunny hours!
I think you're right! The behavior you describe seems more like the battery management system (BMS) managing the charge cycle, rather than the solar charge controller. It’s definitely worth understanding how your specific setup communicates and handles recharging.
Are you saying your batteries take in less power than what they use? That's tough, but yeah, if they’re not keeping up, you really need to manage what’s being drawn versus what’s coming in from the panels.