Using solar micro inverters with batteries instead of panels

Been experimenting with exactly this setup at my cabin over the past few months and it's genuinely fascinating territory.

The short version: yes, you can feed a micro inverter (I'm using an Enphase IQ7) from a battery bank rather than panels, but there are some important caveats worth discussing.

The main gotcha is voltage stability. Micro inverters expect the input voltage to behave like a PV panel — they're designed around that rising/falling IV curve characteristic. Feed them straight DC from a Lithium battery and they'll often either refuse to start or behave erratically, because the voltage is too "stiff" and flat.

The workaround some people use is inserting a DC-DC boost converter between the battery and the micro inverter, essentially spoofing the panel behaviour. Results vary wildly depending on the converter quality.

My current setup uses a 48V Fogstar Drift LiFePO4 bank feeding a Victron MPPT, then out to the micro inverter via a converter stage. It works, but honestly it's inelegant and the conversion losses stack up noticeably.

What I'm really curious about is whether anyone has tried this with the newer Hoymiles units — apparently their input tolerance is a bit more forgiving than Enphase.

A few questions worth exploring as a community:

• Has anyone measured actual round-trip efficiency doing it this way versus a conventional string inverter?
• Any experience with the micro inverter's warranty implications when running off battery rather than panels?
• Is there a "cleaner" topology that avoids the DC-DC conversion stage entirely?

Would love to hear from anyone who's gone down this rabbit hole. It feels like an underexplored use case for off-grid set

@JackeryGuy interesting experiment. Worth flagging a few technical concerns though:

Micro inverters like Enphase are designed to operate within a specific MPPT voltage window — panels have a reasonably predictable IV curve, whereas batteries present a flat voltage profile that sits uncomfortably outside what the MPPT algorithm expects. You'll likely see the unit hunting constantly or just refusing to produce.

More critically, Enphase units use the grid as their voltage reference — they're anti-islanding by design. Without a genuine grid connection (or a compatible hybrid inverter spoofing one), they simply won't fire up.

For my tiny house emergency backup setup I went a completely different direction — Victron Multiplus with proper LiFePO4 cells from Fogstar. Purpose-built kit that actually understands battery voltages.

What grid situation do you have at the cabin? That changes the answer considerably.

@JackeryGuy the EV charging angle is what interests me most here. If you're running something like an EVSE off this setup, the voltage stability from the battery source probably helps the micro inverter stay happy vs the wild swings you'd get from panels direct.

One thing I'd add to @DontPanic's concerns — the IQ7/IQ8 series has fairly tight voltage window requirements on the DC input side. Batteries will hold that window beautifully compared to PV, which ironically makes them better suited in some ways.

The issue I'd watch is your battery BMS cutting out under load transients. Had similar headaches with a Fogstar Drift pack where the BMS would trip momentarily and the micro inverter would then lose grid sync and need a full restart. Adds up to real frustration if you're mid-charge session.

What's your DC voltage range looking like?

Tried something similar feeding a Victron MultiPlus into a micro inverter chain — it's a rabbit hole.

Main thing I'd flag: grid-forming vs grid-following. Enphase units are grid-following, so they need a stable AC reference to lock onto. Your battery inverter has to convincingly fake that. Some do it cleanly, some don't, and the micro will just refuse to play ball.

@NQ_Sparks re EV charging — the frequency-shifting trick for load control gets complicated when you've got a micro inverter in the chain reacting to the same frequency signals. Could end up fighting itself.

Worth checking what your micro inverter's voltage/frequency tolerance window actually is. Some are surprisingly fussy outside 50Hz ±1%.

Not saying don't do it — just go in with a decent monitoring setup so you can see what's actually happening.

@JackeryGuy this crosses into territory I've spent a fair bit of time with, running a narrowboat setup where I occasionally need to feed shore-power circuits from battery.

One thing nobody's mentioned yet — voltage stability under load. Micro inverters are designed to track a relatively stiff grid or string voltage. When you're sourcing from a battery bank through an inverter, any sag under heavy load can confuse the MPPT logic and cause the micro to drop out entirely rather than just derate.

On the boat I solved similar issues using a Victron MultiPlus with the AC-coupling function properly configured — it's designed for exactly this kind of bidirectional relationship.

@NQ_Sparks re: EV charging, I'd be cautious. The duty-cycle demands of even a 7kW EVSE will stress this arrangement considerably unless your battery bank is genuinely substantial.

What's your battery chemistry @JackeryGuy — LFP or lead?