Growatt SPF 5000 ES MPPT Bug? Solar harvest drops and battery charge goes to 0A under AC load

Had this exact gremlin haunting my motorhome setup last summer — turned out the SPF 5000 ES gets a bit confused when AC load suddenly spikes and it briefly prioritises the inverter side, leaving the MPPT looking like it's gone for a tea break.

Few things worth checking:

• Battery type setting — if it's not matched correctly to your actual chemistry, the charge parameters go a bit haywire under load
• Firmware version — Growatt quietly pushed an update that addressed some MPPT prioritisation logic, worth logging into ShinePhone and checking
• AC input sensitivity — if it's set too sensitive it keeps dropping in and out of bypass/inverter mode which confuses the charge controller

I've also seen this with Fogstar Drift LiFePO4 packs where the BMS momentarily sags voltage under load, the Growatt misreads it as "battery full" and drops charge current to 0A like a confused puppy.

Is yours showing any fault codes on the display when it happens, or just silently sulking? Also — are you on grid-tied AC input or purely off-grid? Makes a difference to how it's managing the priority logic.

Mine eventually settled down after a firmware flash and setting charge current manually rather than leaving it on auto — still not as slick as my Victron gear in the shepherd's hut, but it gets the job done without remortgaging the caravan.

Anyone else on here running the SPF 5000 ES long-term? Curious whether this is widespread or just our particular units being dramatic. 🔌

@MarineGeoff that prioritisation issue is well documented on the Growatt forums. The SPF 5000 ES runs a fairly crude power management loop — when AC load spikes, it momentarily drops MPPT current to zero whilst it recalculates the power budget. On my narrowboat I saw the same with a Victron MultiPlus, though Victron's control loop recovers in milliseconds rather than the several seconds Growatt takes.

Worth checking:

• Firmware — some later versions tightened the loop response
• Battery priority setting — switching from "SBU" to "SOL" mode sometimes stabilises it
• Input voltage threshold — if set too conservatively the MPPT backs off prematurely

The 0A charge readout during the glitch is almost certainly just the display catching the trough, not actual sustained dropout. Log it with a Victron SmartShunt or similar to see what's actually happening versus what the Growatt screen claims.

Seen this with my shepherd's hut setup — not Growatt but similar behaviour on cheaper hybrid inverter-chargers when load transients hit. The MPPT and inverter share processing and one starves the other briefly.

Worth checking your battery voltage setpoints first. If charge absorption voltage is set too close to your resting voltage, any wobble and the BMS sees a "full" battery and the charger backs off to 0A. Looks like a bug, usually isn't.

@MarineGeoff what's your battery chemistry — LiFePO4 or lead? And what are your charge parameters set to? That'll narrow it down considerably before going down the firmware rabbit hole.

Also check whether the drop coincides with the AC load crossing a specific wattage threshold — that pattern points more to the prioritisation issue @LH_Marine mentioned rather than a setpoint problem.

Worth checking your charge source priority settings in the Growatt parameters. On mine I had to manually lock PV as the first priority — the default often lets the unit deprioritise solar harvest mid-cycle when it senses a load spike.

Also look at parameter 29 (charge current limit) — sometimes resets itself after a firmware quirk.

If you've got a Victron BMV or similar logging actual battery amps, cross-reference that against the Growatt's own display. I've caught my unit lying about charge current before — shows 0A when it's actually doing something, and vice versa.

@SaltyHiker's right that this isn't unique to Growatt — but the SPF 5000 ES specifically has a known lag in its MPPT resumption after load transients. Might be 2–3 seconds, might be 30. Firmware version matters here.

@BatteryRay has the right instinct on the priority settings, but there's another culprit worth investigating: the battery voltage sensing during high AC draw.

On my LDV-based build I found the SPF 5000 ES was reading a false voltage sag on the battery bus the moment the inverter kicked hard — it interpreted that as a near-depleted battery and throttled MPPT charge current accordingly. Classic ground loop / voltage sensing issue.

A few things that helped:

• Move your battery voltage sense wires directly to the terminal lugs, not midway along the cable run
• Check your DC cable sizing — undersized cable = real voltage drop = the inverter isn't entirely wrong to throttle
• Parameter 29 (battery charge current limit) can sometimes interact oddly with load compensation firmware

Worth logging with a Victron SmartShunt if you have one handy — the data will tell you immediately whether it's a sensing artefact or genuine throttling.