Sunsynk problems & fault guides — every common fault covered
Every Sunsynk fault guide in one place. Battery not charging, cheap rate not working, Solarman offline, no backup during a power cut — each page walks through the diagnostic path, the common causes, and whether it can be fixed remotely. Select your fault below.
Tell us what you're seeing — fault code, what Solarman shows, what changed recently, what the battery is doing. We'll identify the fault and give you the fastest path to a fix.
Book a Remote Diagnostic — from £75 → Solar not working at all?Independent — not affiliated with Sunsynk Energy.
Battery charging & discharging problems
The most common Sunsynk call-outs. Nearly always a configuration issue — TOU schedule, grid charge enable setting, or SoC threshold — that can be resolved without a site visit.
Charge window set correctly in Solarman but battery stays at minimum SoC. Covers TOU schedule errors, grid charge enable being off, SoC minimum threshold, and Octopus tariff clock offset issues.
See Sunsynk-specific guide →Sunsynk integrates with Octopus Agile, Intelligent, and Go but the TOU schedule must be precisely configured. Common issues: charge windows offset by BST/GMT, grid charge enable toggle, SoC target not high enough.
See Sunsynk-specific guide →Battery shows charged but the house draws from the grid at peak times. Usually a discharge schedule configuration error, SoC minimum set too high, or an EPS battery reserve threshold preventing normal discharge.
See diagnostic guide →Solar output & grid connection faults
Low or zero solar generation, unexpected grid imports, and EPS backup not activating during a power cut. Check Solarman for DC input voltage and error codes first.
Sunsynk hybrid inverter powered but showing zero or low generation. Check Solarman for DC input voltage readings. Common causes: DC isolator tripped, string fault, grid overvoltage curtailment, or export limit active.
See diagnostic guide →House lost power during a grid outage despite a charged Sunsynk battery. EPS (Emergency Power Supply) mode must be correctly wired and enabled in settings. Also covers EPS SoC reserve threshold and load circuit configuration.
See diagnostic guide →Solarman, WiFi & datalogger faults
The inverter keeps running when Solarman goes offline — only remote monitoring is lost. Usually a datalogger WiFi issue after a router change or broadband switch.
Solarman (formerly PVMaster) shows no data or last updated hours ago. The inverter is still operating — only monitoring is affected. Router changes, password updates, and logger hardware failure are the most common causes.
See diagnostic guide →Sunsynk dataloggers require 2.4GHz WiFi. Many monitoring failures after a router upgrade are caused by the new router defaulting to 5GHz or using band steering. We reconfigure the datalogger remotely from your Solarman access details.
See diagnostic guide →Sunsynk fault code index
Sunsynk fault codes appear in the Solarman app and on the inverter display. Common code groups cover grid voltage faults (E02X series), battery communication errors, DC bus faults, and temperature protection trips. Share your exact code when you book — we identify the root cause as part of the remote diagnostic.
How we approach Sunsynk fault diagnosis
Every fault guide above is built from real Sunsynk diagnostic sessions. The pattern we see most often is a homeowner who has set up their charge schedule correctly — the windows look right in Solarman — but the battery still isn't charging at the cheap rate. The root cause is almost always one of three things: the grid charge enable toggle, an SoC minimum threshold that's too high, or a BST/GMT offset after the clocks changed. None of these require a site visit.
Sunsynk's Solarman monitoring platform gives us a detailed view of charge/discharge history, TOU schedule logs, DC input voltage, and fault code registers. That's why most Sunsynk problems — including grid disconnection faults and monitoring issues — can be fully diagnosed and resolved remotely, often in a single session.
If your fault isn't listed above, or you've worked through a guide and the problem persists, book a remote diagnostic. We're independent from Sunsynk Energy and your installer — you get an objective second opinion on what's actually wrong and what needs doing.
Sunsynk problems — common questions
The most common Sunsynk problems are: battery not charging on the cheap rate overnight (TOU schedule or grid charge setting error), Solarman app showing offline (datalogger WiFi connectivity lost after a router change), battery not discharging at peak times (SoC minimum threshold too high or discharge schedule misconfigured), and grid disconnection faults (AC voltage or frequency excursion outside G98/G99 limits). The vast majority are configuration issues, not hardware faults.
The most common causes are: the TOU (Time of Use) charge window not matching your tariff's cheap rate period, the grid charge enable setting switched off, or the battery SoC minimum threshold set too high to allow meaningful charging. Sunsynk integrates with Octopus Agile, Intelligent, and Go — but the TOU schedule must be precisely configured. BST/GMT offsets also catch people out after the clocks change. See the Sunsynk cheap rate guide for the full diagnostic path.
Yes — the inverter continues generating solar, charging the battery, and running your home normally even when Solarman shows offline. Only remote monitoring is lost. The most common cause is the WiFi datalogger losing connection after a router change, broadband switch, or firmware update. The datalogger needs to be reconfigured to connect to the new network. See the monitoring offline guide for step-by-step instructions.
Yes — the majority of Sunsynk faults are fully diagnosable and fixable remotely. We review Solarman monitoring data, TOU schedule history, fault code logs, and charge/discharge waveforms in a single session. On-site visits are only needed for physical hardware faults — DC cable issues, CT clamp repositioning, or component replacement. Most tariff, schedule, and monitoring problems are resolved without anyone visiting your home.
Can't find your fault, or the guide didn't fix it?
A remote diagnostic session finds the exact cause using your Solarman data, error history, and TOU schedule — then gives you a clear repair plan. Most Sunsynk problems are resolved in a single session.