Growatt Inverters throttle battery charging

Been doing a bit of reading on this after noticing my Growatt acting oddly on cloudy days — seems like it genuinely does throttle charging when it detects certain conditions, though I'm still not 100% clear on whether it's a firmware thing or a hardware limitation baked in from the factory.

Has anyone actually dug into the settings via ShinePhone or the web portal to see if there's a parameter that controls this behaviour? I've seen some mentions of "charge current limits" in the advanced settings but mine seem greyed out depending on which mode I'm in.

For context, I'm running this in a van conversion setup — 48V LiFePO4 pack (Fogstar cells) with a fairly modest solar array on the roof. The throttling seems most noticeable when the batteries are between roughly 40–70% SoC, which is exactly when I'd expect it to be pushing hardest.

A few questions for anyone who's looked into this:

• Is this a BMS communication issue (I'm not using CAN bus between the inverter and battery)
• Could it be the inverter derate-ing due to temperature inside the unit?
• Has anyone found a firmware version that behaves better?

Interested whether Victron users see similar patterns or if this is more of a Growatt-specific quirk. Wondering if it's worth the hassle of wiring up the CAN comms properly to give the inverter proper visibility of the battery state rather than just relying on voltage-based guessing.

@VanLee yes, Growatt SPF series definitely has some quirky charge management behaviour. What you're likely seeing is the battery voltage-based absorption throttling — it backs off current as it approaches the absorption voltage set point, which is normal, but Growatt's implementation can feel quite aggressive compared to something like a Victron MultiPlus.

Worth checking:

• Your absorption and float voltage settings match your battery chemistry exactly
• Battery type setting isn't on the wrong preset (caught me out with my LiFePO4 setup)
• Firmware is current — some earlier versions had genuinely buggy charge curves

On overcast days the solar input dropping in and out can also confuse the charge controller into resetting its absorption timer repeatedly, which looks like throttling but is actually something else entirely.

What battery are you running? That'd help narrow it down.

@VanLee what you're likely experiencing is the Growatt's built-in charge current limiting when DC input voltage drops below a certain threshold — it's protecting the inverter more than managing the battery intelligently.

I ran a Growatt SPF 3000TL on my first van build and saw exactly this on overcast days. The unit was essentially de-rating itself because the PV voltage was wobbling around the MPPT's lower operating boundary.

Worth checking two things:

1. Your MPPT input voltage range — if panels are dropping below ~60V on the Growatt's tracker, it'll throttle without warning
2. Battery voltage settings — the default bulk/absorption figures are quite conservative from the factory

If you're running Lithium, the default profiles are almost certainly wrong. I'd pull up the parameter list (it's buried in the manual) and cross-reference against your actual battery spec. Fogstar Drift cells in particular need tweaking from defaults.

@MarinePhil @RetiredPlumber my Victron just quietly gets on with it while my Growatt throws a wobbler like a toddler denied a biscuit.

Seen this exact behaviour on my narrowboat last winter. The Growatt was doing strange things whenever cloud cover dropped the panel voltage into that awkward middle range — not low enough to stop charging entirely, but not stable enough for it to commit.

What I eventually traced it to was the unit hunting between bulk and absorption modes repeatedly rather than settling. Every cycle it'd throttle back and restart. Frustrating to watch on the display.

@MarineKaren your Victron comparison is fair — the MPPT algorithm handling is genuinely more refined. That said, once I tuned the Growatt's battery voltage parameters properly (I was running slightly conservative settings from a hospital backup mindset), the throttling became far less dramatic. Worth double-checking your absorption voltage isn't set too conservatively — that alone can cause this hunting behaviour on marginal solar days.