Growatt SPF 04 — Low Battery Voltage

What it means: The inverter has stopped drawing from the battery because the voltage it reads at its DC terminals is below the cut-off. Growatt's own troubleshooting guide is emphatic that on a lithium system this is most often a communication problem rather than a flat battery — if the inverter cannot talk to the BMS it falls back to a default profile and can report 04 while the pack still holds useful charge. On lead-acid and tubular banks it usually means what it says.

Why does Growatt show 04?

• The battery is genuinely discharged after a long outage, or loads were left running overnight with no charge source
• Lithium BMS protocol mismatch, so the inverter receives no valid state of charge — Growatt notes only some Pylontech and Dyness models communicate with these inverters
• Warning 20 present at the same time, which Growatt's guide treats as the root cause with 04 as the symptom
• Undersized or loose battery cable, so voltage drop under load makes the pack look flatter at the inverter than it actually is at the terminals
• An aged tubular or lead-acid bank that no longer holds voltage under load

The Pakistan factor

This is the most common Growatt off-grid complaint after a long load-shedding block, and it is also the most commonly mis-diagnosed. Two local patterns produce false 04 alarms. First, the DIY tubular-to-lithium upgrade — the pack is swapped but program 05 is left on USE, so the inverter never reads the BMS and works from a lead-acid voltage table that does not fit the pack. Second, locally assembled lithium packs with generic BMS boards that do not speak the Pylontech or Dyness protocol Growatt supports, which typically raise 04 and 20 together. The third is purely mechanical — undersized battery cable on a long run to an outdoor battery cabinet. Voltage drop at 100 A over thin cable is not subtle, and no setting change will fix it.

How to fix it

1. Read the battery voltage on the inverter display and note whether 04 appears the instant a heavy load starts. A voltage that collapses only under load points at cabling or a tired battery, not at a setting.
2. Check whether warning 20 is showing as well. If it is, treat this as a BMS communication fault first — the low-battery reading is downstream of it.
3. Safe for a homeowner — confirm program 05 matches the battery you actually own. Growatt specifies USE for lead-acid and US2 or the brand codes L01 and L02 for lithium. A lithium pack left on the lead-acid profile is a common cause of both false 04 alarms and real over-discharge.
4. Safe for a homeowner — reduce load, let the system charge from grid or PV, and see whether the fault clears on its own.
5. Do not lower the cut-off voltage below the range the manual permits in order to keep the lights on longer. That is how a tubular bank is destroyed in a single season and how a lithium pack is driven into cell under-voltage.
6. Do not open the battery, and do not try to wake a protected lithium pack by connecting a charger straight to it. If a pack has latched into under-voltage protection, Growatt's guide sends you to the battery supplier — that is the correct answer, not a workaround.
7. If the voltage measured at the battery terminals is normal but the inverter still reads low, stop. That points at the sample circuit or firmware inside the inverter. Call your installer or Growatt service.