I'm exploring a project to create a battery backup system using solar power for extended runtime. I'm thinking about utilizing an inverter-charger alongside LiFePO4 batteries and solar panels with a charge controller tied to my battery bank. The issue I'm facing is that the solar panels wouldn't be effective unless there's an outage. I'm looking for ways to make the most of the solar power generated without having a grid connection. Ideally, I would like to set up something like an inverter-charger with PV input to utilize the DC power directly when it's available. Would I just need to run an inverter constantly off the battery bank along with an AC to DC charger that only charges the batteries to 50%, while a solar charge controller takes it up to 100%?
5 Answers
As others mentioned, any hybrid or off-grid inverter will work for you. I’ve got an EG4 6000XP linked to a dedicated sub-panel. It kicks in "instantly" during a power outage. Plus, I’m on a time-of-use plan, so I go "off-grid" for six hours on weekdays and cut my bill by $120 last month! Just keep in mind that the EG4 won't allow backfeeding like many hybrid models; solar can go only to the batteries or to your loads, not both at once.
You've got plenty of good advice already, but I’m curious about what you plan to power with your system? Are you looking to power dedicated circuits in your home or something else? Running a backup for a house means you’ll need a transfer switch. I rely on an off-grid system for 80% of my house and another setup that runs almost exclusively on it, including larger appliances. I have transfer switches installed so I can switch back to the grid if necessary.
You can definitely achieve what you're asking for with a hybrid inverter. Technically, it connects to the grid, but you don't have to sell any excess back to them. Another option is to set up a critical loads panel that utilizes solar power while the rest of your system remains connected to the grid.
For your setup, the Franklin inverter in self-consumption mode would be ideal since it uses solar efficiently without exporting to the grid. If you go for AC coupling, it will control the entire system to charge your batteries effectively.
What you're looking for sounds like what any hybrid inverter can do. For instance, the EG4 6KXP is categorized as off-grid but offers hybrid capabilities without grid export. I have a complete Victron setup, and it powers my house using solar and batteries. If the batteries run low, the grid kicks in as a backup just like a generator would.