Hey everyone! I'm wrapping up decisions for our RV solar system and could use your thoughts. We currently have a 24V LiFePO4 battery bank with four LionEnergy Safari UT1300 batteries in a 2S2P configuration, and we are planning to upgrade to at least a 400Ah battery bank at 24V in the next year. We're starting with 6 solar panels and eventually want to add 2 more for a total of 8. We're considering two options for our Victron MPPT charge controllers. The first option is the Victron SmartSolar MPPT 250|85 paired with 250W 24V panels, which would be wired in 2 to 4 panel strings. This option offers higher string voltage, meaning lower current, better efficiency, and easier wiring. The second option is the Victron SmartSolar MPPT 150|70 with 250W 12V panels. While this is a lower-cost option, it comes with higher current, requiring thicker wires, more voltage drop, and less flexibility in how we string the panels. We want our setup to be clean, efficient, and expandable, and all our components will be from Victron: Multiplus-II, Cerbo GX, Lynx busbars, etc. Also, the backer board measures 96" x 21", so space is a consideration too. What would you choose and why? Any lessons learned or regrets regarding the voltage selection? Thanks for your insights!
2 Answers
When looking at solar panels, don’t just think 12V or 24V; check the voltage ratings on the back of the panels. A "12V" panel typically has a voltage of around 20V open circuit. So, keep that in mind when making your choice!
You can actually use more than one MPPT with your battery bank, just not connected to the same set of solar panels. Using two MPPTs might give you more flexibility for placement or budgeting. Just be aware this can get a bit messy if you're not careful!
Do the MPPTs need to be compatible with each other? Or can you just add another one without any issues?