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Fault guide · GivEnergy battery / DC circuit

GivEnergy Battery DC MCB Keeps Tripping

The DC MCB (battery isolator) on your GivEnergy system has tripped and the battery is disconnected from the inverter. The two main causes are poor cable termination at the battery DC connections and buck-boost converter failure inside the inverter. This guide covers how to tell the difference — and what happens next. For related symptoms, see our inverter not turning on guide.
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  • DC MCB reset is safe to try yourself
  • Immediate re-trip = inverter fault, not battery
  • Cable termination and buck-boost causes covered
DC MCB faults need proper diagnosis

A tripping DC MCB can mean a £50 cable re-termination or a £1,495+ inverter replacement. The fault codes and trip pattern tell us which — we can check remotely before anyone visits site. Send us your fault codes and we'll tell you what you're dealing with.

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jill brocklehurst · Jul 2026 Google
All problems Battery not charging Portal offline CAN comm fault Red light flashing EPS not working DC MCB tripping Inverter won't start Firmware CT clamp Fault codes →
Understanding the DC MCB

What the battery DC MCB does — and why it trips

The DC MCB (miniature circuit breaker) sits between your GivEnergy battery and the inverter. It is the primary safety device protecting the DC battery circuit from overcurrent and short-circuit faults.

NORMAL OPERATION

Closed circuit — handle UP

When the DC MCB handle is in the UP position, the battery is connected to the inverter. DC current flows through the MCB in both directions — charging from the inverter and discharging to the inverter. The MCB is rated at 100A on most GivEnergy systems, matching the maximum battery discharge current.

TRIPPED STATE

Open circuit — handle DOWN or mid-position

When the MCB trips, the handle drops to the DOWN position (or a middle position on some models). The battery is completely disconnected from the inverter. No charging or discharging occurs. The battery LEDs may still show green because the battery itself is fine — the MCB has simply isolated it from the inverter.

WHY IT TRIPS

Overcurrent or short-circuit detected

The DC MCB trips when it detects current exceeding its rating. This is a safety mechanism. The fault is almost never the MCB itself — it is doing its job. The underlying cause is either a wiring fault creating a short-circuit path, or an inverter component failure drawing excessive current from the battery.

The DC MCB is not an AC breaker. Do not confuse it with the MCBs in your consumer unit. The DC MCB is specifically for the battery-to-inverter DC circuit. If the MCB in your consumer unit is also tripping, see our inverter not turning on guide — that is a separate issue affecting the AC side.
Cause 1 — most common
Most common

Poor cable termination — loose or missing ferrules on DC battery cables

The battery DC cables carry up to 100A. If the cable ends were not properly ferrule-crimped during installation, or if the terminal screws have loosened over time, the connections develop high resistance. High resistance at these currents causes arcing, heat build-up, and intermittent overcurrent spikes that trip the DC MCB.

How this happens

→GivEnergy specifies 16mm² tri-rated cable with bootlace ferrules crimped onto the stripped ends before insertion into the inverter DC terminals.
→If the installer stripped the cable and inserted bare copper strands directly into the terminal block, the strands splay and the connection loosens over time with thermal cycling.
→A loose terminal develops micro-arcing under load — especially during high-current events like the battery ramping to full discharge. The MCB sees this as an overcurrent spike and trips.
→The problem is intermittent. The MCB may reset fine and hold for days or weeks before tripping again. This makes it hard to diagnose without a physical inspection of the cable ends.

How an engineer fixes it

→Isolate the DC circuit (MCB off, battery shutdown procedure)
→Remove the battery DC cables from the inverter terminal block
→Inspect cable ends — look for discolouration, heat damage, or bare strands without ferrules
→Crimp appropriate bootlace ferrules (16mm²) onto each cable end using a proper ratchet crimping tool
→Re-insert the ferrule-terminated cables into the terminal block and torque to manufacturer specification
→Test under load — confirm no further tripping over a monitoring period
How to tell this is your problem: the DC MCB holds after a reset for a period (minutes, hours, or days) before tripping again — typically during a high-draw event like the battery ramping to full discharge in the evening. If the MCB trips immediately when you flip it up, that pattern points to cause 2 below (inverter buck-boost failure) rather than cable termination.
Cause 2 — inverter fault
Inverter internal fault — requires repair

Buck-boost converter failure — MOSFET short-circuit inside the inverter

The GivEnergy hybrid inverter contains a buck-boost DC-DC converter that regulates voltage between the battery pack and the inverter's DC bus. This converter uses power MOSFETs (transistors) as high-speed switches. When a MOSFET fails short-circuit — which can happen due to a power surge, thermal stress, or manufacturing defect — it creates a direct low-resistance path that draws excessive current through the DC MCB.

How to recognise this fault

→The DC MCB trips immediately when you flip it to the UP position — it will not hold even for a second
→You hear rapid clicking from the inverter (10–12 cycles) as the relay attempts to connect, followed by the MCB tripping to red
→The GivEnergy portal or app shows the fault message Battery short circuit; inverter fail
→The battery LEDs are green when the DC MCB is OFF — the battery itself is healthy, the fault is in the inverter's power electronics

What happens next

→Leave the DC MCB in the OFF (down) position to prevent further damage to the MCB contacts
→The inverter will continue to operate solar generation on the AC side — you only lose battery charging and discharging
→Check your GivEnergy warranty status — the standard warranty is 5 years, extended to 12 years on some models and purchase agreements
→If under warranty, GivEnergy will arrange inverter replacement (we can manage the warranty claim for you). If out of warranty, inverter replacement starts from £1,495
Do not repeatedly reset a DC MCB that trips immediately. Each reset attempt forces the failed MOSFET to conduct high fault current through the MCB contacts. This degrades the MCB itself over time and can cause contact welding, which turns a replaceable breaker into a more costly repair. If the MCB trips on the first reset, leave it off and arrange a diagnosis.
Cause 3 — less common
Battery BMS

BMS protection event — battery management system triggers a disconnect

The battery management system (BMS) inside the GivEnergy battery monitors cell voltage, temperature, and current. If it detects a condition outside safe limits, it can trigger a protection disconnect. In some configurations this causes the DC MCB to trip as a secondary protection layer. Where the fault codes point to a failed pack rather than wiring or comms, see GivEnergy batteries — supplied and installed at one fixed price.

BMS fault codes to look for

STORAGE_WARN_BMS_SHORT_CURRENT_DISCHARGER The BMS has detected a short-circuit condition on the discharge side. Most commonly caused by incorrect cable polarity or a wiring fault — check that the DC cables are connected to the correct positive and negative terminals.
STORAGE_ERROR_BAT_UNDER_VOLTAGE_FAULT The battery has been deeply discharged — often because the DC MCB was tripped for an extended period and the battery drained its own standby power. The BMS prevents reconnection until the cells are recovered.
STORAGE_WARN_BMS_COM_FAIL The BMS communication cable between battery and inverter has failed. The inverter cannot read battery state, so the BMS disconnects as a safety precaution. Check the communication cable (typically a Cat5-type data cable separate from the main DC power cables).

What to check

→Check the GivEnergy portal event log for the specific BMS fault code — this tells you whether the issue is electrical (polarity, wiring) or communication-related
→If the battery has been isolated for more than a few days, the cells may have self-discharged below the BMS threshold. A controlled recovery charge may be needed
→If STORAGE_WARN_BMS_COM_FAIL is present, check the BMS data cable connection at both the battery and inverter ends — it should be fully seated with the clip engaged
→A battery restart (hold the restart button on the battery for 3–5 seconds) can clear some transient BMS faults. Only do this after checking fault codes first
Reference
Where to find it

DC MCB location by GivEnergy system type

The location of the DC MCB varies depending on which generation of GivEnergy hardware you have. Knowing where it is helps you check its state and communicate clearly with your engineer.

DC MCB / isolator by system type
Gen 1 hybrid External DC MCB — a separate DIN-rail mounted MCB in an enclosure between the battery and inverter. Battery connects via ring terminal lugs on 16mm² tri-rated cable. The MCB handle is typically green or red.
Gen 2 hybrid Integrated DC MCB — built into the battery's all-in-one plug connector system. The isolator handle is on the side of the battery cabinet. Green handle UP = on, handle DOWN = tripped or isolated.
Gen 3 hybrid Integrated DC MCB — similar to Gen 2, built into the battery connector. The Gen 3 batteries (5.12kWh and 9.5kWh) use the same all-in-one plug system with integrated DC protection.
All-in-One Internal DC isolator — the AIO has the battery and inverter in one unit. The DC isolator is accessed via a switch on the unit. On older AIO firmware, EPS-related MCB trips can also occur during grid-to-backup transitions.
External 100A Standalone accessory — GivEnergy sells a standalone 100A DC MCB (rated 80V DC) for systems that need an external isolation point. This is the most common MCB on Gen 1 systems and is sometimes retrofitted on Gen 2/3 installations as an additional safety device.
Related GivEnergy pages
Inverter not turning on

AC-side power issues — tripped consumer unit MCBs, DC isolator positions, and no-display faults.
Red light flashing

Battery and inverter alarm states — fault codes, BMS alerts, and protection events.
Battery not charging

If the MCB was tripped for days, the battery may have self-discharged and need recovery.
Click of death

Relay cycling faults — similar clicking symptoms but from the AC relay rather than the DC circuit.

This is a brand-specific guide. For other GivEnergy issues, see the GivEnergy problems hub. For general battery troubleshooting across all brands, see solar battery not charging.

FAQ

DC MCB tripping questions

The two most common causes are poor cable termination and inverter buck-boost failure. Poor termination means the battery DC cables were not properly ferrule-crimped or the terminal screws have loosened over time, causing intermittent arcing that trips the MCB. Buck-boost failure means a MOSFET inside the inverter's DC-DC converter has failed short-circuit, drawing excessive current the moment the MCB is closed. A third cause is a BMS protection event — the battery management system detects an abnormal condition and the MCB trips as a secondary protection measure.
You can safely flip the DC MCB handle back to the UP position as a first step — this is no different from resetting a tripped breaker in your consumer unit. If the MCB holds and the battery reconnects normally, the trip may have been caused by a transient event such as a grid surge. If the MCB trips again immediately or within minutes, do not keep resetting it. Repeated tripping under a short-circuit condition can damage the MCB contacts and worsen the underlying fault. At that point you need an engineer to diagnose the root cause.
This fault message indicates the inverter has detected a short-circuit condition on its DC battery input. In most documented cases this is caused by failure of the buck-boost converter MOSFETs inside the inverter — the power transistors that regulate voltage between the battery and inverter have failed in a short-circuit state. The battery itself is usually fine, which is why the battery LEDs stay green when the DC MCB is switched off. The inverter typically needs repair or warranty replacement.
A free remote diagnostic reviews fault codes and event logs — pay only if we fix. If the cause is poor cable termination, an on-site visit to re-terminate and re-torque the DC cables is typically £245–£295 depending on the number of connections and accessibility. If the inverter's buck-boost circuit has failed, the inverter may be covered under GivEnergy's 5-year or 12-year warranty — we can check your serial number and handle the warranty claim process. Out-of-warranty inverter replacement starts from £1,495.
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DC MCB keeps tripping? Send us the fault codes — we'll tell you what you're dealing with.

The trip pattern and portal fault codes tell us whether this is a cable re-termination job or an inverter replacement. We can diagnose remotely before anyone visits site — saving you a wasted call-out if it turns out to be a warranty claim.

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