I'm nearing the finish line on my solar DIY project and have a few questions regarding the compatibility and wiring of my equipment. Here's what I have so far: 16 CATL LIFEPO4 3.2Vdc cells (314Ah), 2 Victron 100/50 MPPT charge controllers, 1 JK BMS (4s-8s), and 8 Eco-Worthy 195W panels with a max power voltage of 20.02V and max current of 9.65A. I'm considering setting up my battery bank to be 24V and using a DC-to-DC converter for my 12V inverter and fridge, especially since I'll be getting a 24V 6000W inverter soon. How should I configure my panel strings for this setup? I was thinking of having 4 panels, connecting 2 in series and then 2 in parallel to yield 40V at 20A per string. Additionally, if I wanted to add more panels of the same specs, how many could I incorporate with my existing equipment to optimize the charge rate from the MPPTs? Would adding 2 panels in series to each string be feasible? I'm currently aware that my system is oversized for my needs, but I'm planning for future expansion.
3 Answers
You can definitely do an 8s2p battery bank at 24V, which should work just fine. You’ll just need to use a lot of bus bars for proper parallel wiring. If you're unsure about the configuration, I found this helpful setup image for reference: [link].
Since this is for a small cabin setup, it sounds practical. Since your fridge is 12V and you're using some other appliances, I'd agree that a 24V battery configuration is the way to go. However, it does seem like you might need another BMS since you only have a 4s-8s for 16 cells. Adding a few more panels could really boost your system's efficiency!
You're correct to focus on the Voc of around 25V. If you add 20% safety, that brings you to about 30V. With your Victron having a maximum of 100V, you can safely connect up to 3 panels in series. So, the ideal setup would be 9 panels total—3 series of 3 panels each in parallel. Just remember, at 24V, your Victron will efficiently handle up to 1200W worth of panels, which is way better than sticking with a 12V battery. Don’t forget you’ll need that DC-DC converter for your fridge, too!
So just to clarify, would that mean I can run 18 panels total with 2 MPPTs if I'm doing the 3 in series, 3 in parallel setup?
Thanks for sharing that image! It really helps clarify the setup!