Hey everyone! I could use some help with choosing the right size controller for my off-grid setup. I have a small battery that I want to keep charged throughout the year mainly for a couple of devices: a cellular trail camera for security and a cell phone signal booster. I'm considering using a Victron controller rated at 75v 15a. The inputs seem fine, but the output seems a bit low. Is it alright to undersize the output for my small battery? I don't mind limiting the output, but I want to make sure this is a safe choice. An alternative could be a Rich 20a controller, but I'm not too keen on the extra buttons and settings.
I've got two 180w solar panels set up in series. I've previously used this configuration with my Ecoflow Delta Pro, and I like the idea of keeping it the same so I can easily switch back and forth between charging my battery and the Delta Pro when I reach my camp without having to fiddle with the cables.
2 Answers
For lead-acid batteries, charging them at around 0.2 to 0.5 C is recommended, translating to about 50-150 watts. In your case, a smaller setup with a 10 amp MPPT or PWM controller along with a 100-watt panel would be the best combo, ensuring you're not overloading the battery while keeping things efficient.
You should ideally use a 30-35 amp MPPT controller to optimize the output from your two 180w panels. However, if you're fine with a little less efficiency, a 15 amp controller will work for your needs. Just keep in mind that you might not be getting the fullest potential out of your panels.
Got it! If I'm okay with saving some cash and not maxing out the panels, I'm good to go with the 15 amp, right?