If your campervan or motorhome solar panel is not charging the leisure battery, the problem may be caused by poor light, shading or a battery that is already full. It could also involve a blown fuse, loose connector, incorrect controller settings, damaged roof cable, battery fault or failed solar charge controller.
The first step is to establish whether the system has stopped charging completely or is simply producing less power than expected.
A controller showing only a few watts on a cloudy winter morning may be operating normally. A controller showing no panel voltage in bright sunshine points towards a different problem.
At WeConvert, we provide campervan and motorhome solar fault finding from our Blackburn workshop. We inspect the panel, cabling, protection, charge controller, battery connections and charging settings before recommending replacement parts.
Quick Solar-Charging Fault Guide
| Symptom | Possible causes |
|---|---|
| Solar controller is completely blank | No battery connection, blown battery-side fuse, isolator off or controller fault |
| Controller shows panel voltage but no charge current | Battery full, battery disconnected, incorrect settings, BMS restriction or controller disabled |
| Controller shows zero panel voltage in daylight | Roof wiring fault, disconnected plug, blown PV protection, reversed polarity or damaged panel |
| Solar output is much lower than expected | Cloud, low sun, shade, dirt, panel damage, high battery state of charge or system losses |
| Battery charges on hook-up but not from solar | Solar-panel, controller, fuse or solar wiring fault |
| Solar works intermittently | Loose connection, damaged roof cable, poor crimp, moisture or shading |
| Controller shows night mode during daylight | Insufficient panel voltage, disconnected panel, shading or PV wiring problem |
| Lithium battery will not accept solar charge | Battery full, low-temperature protection, BMS disconnect or incorrect charge settings |
| Solar controller becomes very hot | Poor ventilation, overload, loose connection or unsuitable installation |
| Battery still goes flat despite solar | Solar yield too low, battery fault, excessive loads or another charging problem |
These are starting points rather than confirmed diagnoses. Several different faults can create the same symptoms.
How a Campervan Solar-Charging System Works
A typical campervan or motorhome solar system contains:
- One or more roof-mounted solar panels
- Solar cables and weatherproof roof entry
- Connectors or a junction box
- A solar charge controller
- Protection such as fuses, breakers or isolators
- A leisure battery or battery bank
- Monitoring through a display, app or battery monitor
The solar panel produces DC electricity when exposed to daylight.
The charge controller regulates that energy into a charging profile suitable for the leisure battery. Depending on the system, it may use either:
- PWM control
- MPPT control
An MPPT controller can operate the solar panel at a more effective voltage and convert the available energy into a suitable battery-charging output.
The controller does not necessarily deliver maximum current all day. Charge output changes according to:
- Available sunlight
- Panel temperature
- Shading
- Battery state of charge
- Battery voltage
- Controller limits
- Battery settings
- Electrical loads currently operating
A low charge reading does not automatically mean the solar system has failed.
First Check: Is the Battery Already Full?
Once the leisure battery is full or close to full, the solar controller should reduce the charging current.
It may move through charging stages described as:
- Bulk
- Absorption
- Float
- Storage, on some systems
During bulk charging, the controller normally delivers as much available power as the battery and controller settings permit.
As the battery approaches full charge, the controller reduces the current to prevent overcharging. A display showing only a few watts can therefore be completely normal when the battery is full.
Victron and Renogy both advise that solar output may reduce significantly once the connected battery reaches its full or float-charging condition.
Before diagnosing a fault, check:
- Battery state of charge
- Controller charge stage
- Battery voltage
- Whether any significant loads are operating
- Whether solar output increases after some energy has been used
Turning on a suitable 12V load for a short period may cause the controller output to increase, but do not deliberately discharge the battery heavily simply to test the solar panels.
1. Cloud, Low Sun or Poor Weather
Solar-panel output varies enormously with the available light.
Factors include:
- Cloud thickness
- Time of day
- Season
- Sun angle
- Vehicle orientation
- Rain
- Mist
- Nearby buildings
- Trees
- Roof furniture
- Panel temperature
A panel may still show voltage in weak daylight while producing very little usable current.
This is particularly noticeable in Blackburn and across Lancashire during autumn and winter, when shorter days, lower sun angles and persistent cloud can reduce daily solar generation substantially.
Do not judge the system solely from one reading taken:
- Early in the morning
- Late in the afternoon
- During heavy cloud
- Beneath trees
- Inside a building
- With the van parked close to a wall
Where practical, assess it around the middle of a bright day with the panels clear of shade.
2. Part of the Solar Panel Is Shaded
A relatively small shadow can reduce panel output more than many owners expect.
Common sources of shade on campervans and motorhomes include:
- Rooflights
- Pop-top roofs
- Satellite dishes
- Aerials
- Roof bars
- Solar-panel mounting brackets
- Ventilation fans
- Awning hardware
- Nearby trees
- Buildings
- Another parked vehicle
The effect depends on:
- Panel construction
- Internal bypass diodes
- Whether panels are wired in series or parallel
- Which part of the panel is shaded
- Controller type
A panel that performed well before another roof accessory was fitted may now be shaded during part of the day.
Check the complete roof from several angles rather than looking only from ground level.
3. Dirt, Leaves or Debris on the Panel
Dirt can reduce the amount of light reaching the solar cells.
Possible contamination includes:
- Road film
- Tree sap
- Bird droppings
- Leaves
- Moss
- Dust
- Pollen
- Snow
- Protective film accidentally left on a new panel
Clean panels according to the panel manufacturer’s instructions. Avoid harsh chemicals, abrasive tools and standing directly on the campervan or motorhome roof.
A badly positioned flexible panel may also collect dirt around low spots or edges.
Cleaning will not repair a failed panel, but it is a sensible first check where output has reduced gradually.
4. The Solar Controller Has No Battery Connection
Most solar charge controllers need a reliable battery connection to operate and charge correctly.
Possible causes of a missing battery connection include:
- Blown fuse between controller and battery
- Open circuit breaker
- Battery isolator switched off
- Loose cable
- Failed crimp
- Corroded terminal
- Disconnected battery
- Lithium battery BMS protection
- Incorrect wiring
A controller may appear partly alive because it is receiving power from the solar panel, yet deliver little or no charge because it does not have a proper connection to the battery.
Victron identifies blown fuses, open breakers, loose cables, poor crimps and wiring errors as common reasons a controller may not have a usable battery connection.
Compare:
- Battery voltage measured at the battery
- Battery voltage reported by the controller
- Voltage measured at the controller’s battery terminals
A meaningful difference can point towards resistance or a break in the wiring between the controller and battery.
5. The Battery-Side Fuse Has Blown
A fuse should normally protect the cable between the solar controller and leisure battery.
If this fuse blows, the controller may stop charging even though the solar panels are still producing voltage.
Possible reasons include:
- Short circuit
- Reverse polarity
- Loose connection
- Cable damage
- Water ingress
- Incorrect fuse rating
- Controller fault
- Work recently carried out on the battery
- Accidental contact between positive wiring and the vehicle body
The fuse may be located:
- Close to the leisure battery
- Beside the charge controller
- Inside a combined distribution board
- Within an inline holder
- Behind furniture or a removable panel
Do not assume a fuse is intact because it looks normal through its casing. Testing may be required.
Replace it only with the correct type and rating. If the replacement blows, stop and investigate the cause rather than fitting a larger fuse.
6. A Solar Isolator or Circuit Breaker Is Off
Some installations include an isolator or circuit breaker between:
- Solar panel and controller
- Controller and battery
- Both sides of the controller
It may have been switched off during:
- Battery replacement
- Electrical maintenance
- Winter storage
- Other conversion work
- Fault diagnosis
Check that every relevant switch is in its correct operating position.
A circuit breaker that repeatedly trips may indicate a wiring or equipment fault and should not simply be reset over and over.
7. Loose or Damaged Solar Connectors
Roof-mounted solar panels commonly use weather-resistant plug connectors.
Problems can arise where connectors are:
- Not fully engaged
- Poorly crimped
- Incorrectly assembled
- Contaminated by water
- Damaged
- Pulled apart during roof work
- Mixed between incompatible manufacturers
- Located where they sit in standing water
A loose solar connector can create:
- Intermittent charging
- Reduced output
- Heat
- Arcing
- Complete loss of panel voltage
- A fault that changes as the vehicle moves
Do not disconnect or reconnect solar plugs casually while the panels are producing power.
Follow the isolation procedure for the specific controller and installation. Solar panels can continue producing voltage whenever they are exposed to light.
8. The Roof Cable Has Been Damaged
Solar wiring can be damaged during:
- Rooflight installation
- Pop-top fitting
- Roof-rack installation
- Replacing an aerial
- Adding another solar panel
- Removing internal ceiling panels
- Furniture installation
- Drilling into hidden cavities
- Sealing or repairing the roof
Possible damage includes:
- Screws through cables
- Crushed insulation
- Cables trapped beneath fittings
- Pulled connectors
- Water entering the cable
- Wiring rubbing against sharp metal
- Poorly supported cable moving while driving
If the solar stopped working immediately after other work was completed, tell the technician exactly what changed.
9. The Solar Cable Entry Is Leaking
The cable gland or roof-entry housing must protect both the wiring and the vehicle interior.
Water ingress can cause:
- Corroded connectors
- Green deposits on copper conductors
- Intermittent charging
- Controller errors
- Damaged interior panels
- Damp insulation
- Short circuits
- Reduced insulation resistance
Inspect around the cable entry for:
- Cracked sealant
- Loose housing
- Movement
- Water marks
- Damp trim
- Corroded wiring
- Previous poor repair work
Do not simply apply more sealant over a dirty or failed joint. The entry may need to be removed, cleaned and resealed correctly.
Our campervan and motorhome repairs and fault-finding service in Blackburn can assess selected solar and roof-entry faults.
10. The Panel Polarity Is Reversed
If the positive and negative solar leads are reversed, the controller may not detect or use the panel correctly.
Some controllers display a reverse-polarity fault. Others may simply show no usable PV input.
Official troubleshooting guidance advises checking the polarity and voltage at the controller rather than assuming that connector colours or labels are correct.
This is particularly relevant where:
- The system has recently been installed
- Connectors have been replaced
- Panels have been rewired
- A new controller has been fitted
- Two different connector types have been joined
- The wiring colours are inconsistent
Do not reverse wiring by trial and error.
Polarity should be confirmed using appropriate test equipment and the manufacturer’s instructions.
11. The Panel Voltage Is Too Low for the Controller to Start Charging
An MPPT controller normally needs the solar-array voltage to rise sufficiently above the battery voltage before charging begins.
The exact threshold varies by controller.
For example, several Victron MPPT models require the PV voltage to be approximately 5V above battery voltage to begin charging and about 1V above battery voltage to continue. Other brands and models may behave differently.
Panel voltage may be too low because of:
- Weak light
- Heavy shading
- Damaged panel
- Incorrect wiring
- Loose connection
- Too few cells for the controller and battery voltage
- Fault within a series-connected array
- Incorrect panel specification
- Excessive wiring loss
This can explain why a controller shows night mode even though there appears to be daylight outside.
The controller manual should be checked for its exact startup requirements.
12. The Charge Controller Has Incorrect Battery Settings
A solar charge controller must use charging parameters suitable for the connected battery.
Settings may include:
- Battery chemistry
- Absorption voltage
- Float voltage
- Charge-current limit
- Temperature compensation
- Equalisation
- Low-temperature charging restrictions
- Tail current
- Absorption duration
Incorrect settings can result in:
- Battery undercharging
- Controller entering float too early
- Excessive charging voltage
- Lithium BMS disconnection
- Reduced battery life
- Controller apparently producing little power
- Charging stopping unexpectedly
Victron warns that charge voltages set too low can cause a controller to treat a battery as fully charged and enter float prematurely.
Do not select a generic “lithium” or “lead-acid” setting without checking the battery manufacturer’s requirements.
Different batteries using the same broad chemistry can still require different charging parameters.
13. The Controller Is Set to the Wrong System Voltage
Many controllers automatically detect whether they are connected to a 12V or 24V battery system.
Incorrect detection can occur where:
- The battery was disconnected while the panel remained connected
- The controller was powered in the wrong sequence
- Battery voltage was unusually low
- Settings were manually changed
- The system has been modified
For many controllers, the recommended installation sequence is to establish the battery connection before connecting the solar input so the controller can identify the system correctly. The exact sequence should always follow the manual for the model fitted.
Do not disconnect and reconnect the system without understanding:
- Which side should be isolated first
- Whether the panel needs covering
- Whether a controller setting must be retained
- How a connected lithium battery will respond
14. The Lithium Battery Is Refusing Charge
A lithium iron phosphate battery may disconnect or restrict charging through its battery-management system.
Possible reasons include:
- Battery is already full
- Battery temperature is too low
- Battery temperature is too high
- Charge voltage is excessive
- Charge current is excessive
- Cell imbalance
- Battery has entered protection mode
- Communication between battery and charger has failed
- Battery-management system fault
Low-temperature protection is particularly relevant during winter.
Some lithium batteries prevent charging when their cells are cold, even though they may still allow discharge. Certain solar controllers can also be instructed by a connected battery-management system to stop charging.
The solar controller may therefore appear healthy while showing zero charge current.
Check:
- Battery app or display
- Recorded battery alarms
- Cell temperature
- BMS status
- Controller error messages
- Battery manufacturer’s charging limits
Do not bypass the BMS or attempt to force charge into a battery that has activated temperature protection.
15. The Leisure Battery Is Faulty
The controller may be producing energy while the battery fails to retain it.
Possible battery symptoms include:
- Voltage rises quickly during charging
- Voltage falls quickly after charging stops
- Battery appears full after a short period
- Usable capacity has reduced
- Equipment cuts out under load
- Battery becomes unusually warm
- Battery casing is swollen or damaged
- Battery repeatedly enters protection mode
A worn lead-acid battery can reach the controller’s target voltage without storing much useful energy.
Replacing the solar controller will not correct a failed battery.
The battery should be tested under appropriate charging and load conditions.
For broader charging diagnosis, read Why Is My Campervan Leisure Battery Not Charging?.
16. The Controller Is Disabled by a Setting or Remote Input
Some charge controllers can be disabled by:
- An app setting
- Remote on/off connection
- Battery-management system
- External control unit
- Vehicle energy-management system
- Low-temperature signal
- User-programmed charge schedule
- Firmware or communication fault
Check the controller status carefully.
A message such as:
- Charger off
- Remote off
- BMS controlled
- Battery full
- Low temperature
- No PV
- Overvoltage
is more useful than simply noting that the output is zero.
Record screenshots before changing settings or resetting the controller.
17. The Controller Is Overheating or Reducing Output
Solar charge controllers produce heat while operating.
They need suitable:
- Ventilation
- Mounting orientation
- Clearance
- Cable sizing
- Environmental temperature
- Protection from direct heat sources
Output may reduce or stop where the controller is:
- Inside an unventilated cupboard
- Mounted beside an inverter
- Close to a diesel-heater duct
- Covered by stored items
- Installed above a warm battery
- Overloaded
- Connected using loose or undersized wiring
Do not cover the cooling fins or ventilation slots.
Discolouration, melted insulation or a burning smell requires immediate investigation.
18. The Solar Panel Has Failed
Solar panels can fail because of:
- Impact damage
- Water ingress
- Internal connection failure
- Cracked cells
- Delamination
- Failed bypass diode
- Corroded junction box
- Cable damage
- Excessive flexing
- Poor installation
Flexible solar panels can be particularly difficult to inspect once fully bonded to a roof.
Possible signs include:
- Correct light conditions but zero panel voltage
- Much lower voltage than expected
- Intermittent output as the roof moves
- Visible bubbles or delamination
- Burn marks
- Cracks
- Hot spots
- Corroded junction box
- One panel in a multi-panel array producing no output
Testing should compare the panel’s measured output with its specifications and the actual light conditions.
A low reading on a dull day does not prove the panel has failed.
19. One Panel in a Multi-Panel System Has a Fault
Some campervans and motorhomes use multiple solar panels connected:
- In series
- In parallel
- Through separate controllers
A fault in one panel, connector or cable can affect the wider array.
The behaviour depends on how the panels are wired.
For example:
- A break in a series circuit may stop the whole string
- One disconnected parallel panel may reduce output but leave the others working
- Mismatched panels can limit performance
- Shading may affect one wiring arrangement more severely than another
- A failed branch fuse can remove one part of the array
Do not alter series or parallel connections without checking the controller’s maximum input voltage and current limits.
20. The Controller Is Too Small for the Solar Array
A charge controller has limits for:
- Maximum PV voltage
- Maximum charge current
- Maximum recommended panel power
- Battery-system voltage
Where additional panels have been added without checking those limits, the controller may:
- Limit its output
- Overheat
- Record an overvoltage fault
- Shut down
- Become damaged
A larger controller is not chosen solely from the advertised panel wattage. Array voltage, current, temperature and wiring arrangement also matter.
Have the system recalculated before adding more roof panels.
21. The Controller Is Working but the Loads Are Using the Energy
A solar controller may show that it is producing power while the battery monitor shows little or no net charging.
For example:
- Solar controller produces 8A
- Fridge, lights and other equipment use 6A
- Battery receives only around 2A
If the loads equal or exceed the available solar power, the battery may continue discharging despite the solar system operating.
Common daytime loads include:
- Compressor fridge
- Inverter
- Laptop charging
- Television
- Ventilation fans
- Diesel heater
- Router
- Control systems
- Standby equipment
Check both:
- Solar-controller output
- Net battery current
They measure different things.
A properly installed shunt-based battery monitor is more useful for understanding total energy flow than relying only on the solar-controller display.
22. The Battery Monitor Is Giving a Misleading Reading
A battery monitor can become inaccurate where:
- It has not been synchronised
- Battery capacity is set incorrectly
- Charge efficiency is incorrect
- Some loads or chargers bypass the shunt
- Battery type has changed
- Cabling has been altered
- The monitor has lost power
- The battery has aged significantly
The solar system may be operating correctly even though the displayed state of charge is wrong.
Check actual voltage, current and controller data before replacing components based solely on a percentage reading.
All current entering or leaving the battery should pass through the monitored side of the shunt, except for specified system connections.
23. The Solar System Is Too Small for the Owner’s Usage
A working solar system may still be unable to replace the energy used each day.
This is common where the vehicle has gained additional equipment such as:
- Larger compressor fridge
- Inverter
- Induction cooking
- Laptop use
- Television
- Electric heating equipment
- Diesel heater
- Wi-Fi system
- Additional lighting
- Lithium battery bank
A 100W panel cannot be expected to support every electrical lifestyle in all seasons.
The important calculation compares:
- Daily electrical consumption
- Expected daily solar generation
- Battery capacity
- Other charging sources
- Time of year
- Intended travel pattern
Adding battery capacity alone does not create more energy. A larger battery merely stores more before it needs recharging.
Safe Checks You Can Make Yourself
Before booking solar fault finding, you can normally check:
- Whether the battery is already full
- Charge stage shown by the controller
- Controller error messages
- Whether the controller is switched on
- Whether solar isolators are on
- Whether the panel is shaded
- Whether the panel is visibly dirty
- Whether the system works in strong daylight
- Whether the battery-side fuse is intact
- Accessible cables for looseness or heat
- Battery app for BMS warnings
- Whether the fault began after other roof or electrical work
- Whether there are signs of water ingress
- Solar output with major electrical loads switched off
- Whether the controller reports panel voltage
Useful photographs include:
- Solar panel and roof layout
- Panel label where accessible
- Roof cable entry
- Solar controller
- Controller screen or app
- Battery and terminals
- Fuses and isolators
- Battery monitor
- Any error codes
- Corrosion or damaged wiring
Do not climb onto the roof unless you have safe access and the roof is designed to support it.
What Should You Avoid Doing?
Do not:
- Fit a larger fuse to stop it blowing
- Bridge a fuse or circuit breaker
- Reverse the solar polarity by trial and error
- Disconnect live solar connectors casually
- Short the panel leads together
- Change battery settings without checking the battery requirements
- Bypass lithium BMS protection
- Add more panels without checking controller limits
- Mix incompatible connectors
- Open 230V charging equipment
- Work beneath an unsupported vehicle
- Replace the charge controller before testing the wiring and battery
- Assume every low reading means the panel has failed
Solar panels can continue producing voltage whenever they are exposed to light, even when the battery isolator is off.
How We Diagnose Campervan Solar Faults
At our Blackburn workshop, solar fault finding may include:
- Discussing when the problem started
- Checking the panel type, number and rating
- Inspecting shading and roof layout
- Reading controller status and fault history
- Checking battery state and battery-management warnings
- Measuring battery voltage at the controller
- Checking battery-side protection and wiring
- Measuring solar-array voltage
- Checking polarity
- Inspecting accessible connectors and cable entries
- Comparing controller output with battery current
- Confirming charging settings
- Testing the system under suitable daylight
- Assessing whether the installed capacity meets the owner’s usage
We do not automatically replace the solar panel because the controller shows low output.
The cause may be a loose connector, blown fuse, incorrect setting, full battery or insufficient sunlight.
Campervan and Motorhome Solar Repairs in Blackburn
WeConvert provides campervan and motorhome solar installation, upgrades and fault finding from our Blackburn workshop.
We can assess suitable issues involving:
- Solar panels
- MPPT and PWM charge controllers
- Solar cable entries
- Panel wiring
- Fuses and circuit breakers
- Battery connections
- AGM, gel, lead-acid and lithium batteries
- Incorrect charging profiles
- Low-temperature lithium charging restrictions
- Battery monitors
- Unexplained low solar output
- Existing self-build solar installations
- Additional solar-panel capacity
- Solar systems installed by another converter
Our Blackburn workshop serves customers from:
- Blackburn
- Darwen
- Accrington
- Burnley
- Rossendale
- Bolton
- Chorley
- Preston
- Wider Lancashire
Learn more about our campervan electrical and solar services in Blackburn.
Where the fault affects more than the solar system, read our guide to campervan and motorhome 12V electrics not working.
Frequently Asked Questions
Why is my campervan solar panel not charging the battery?
Common causes include a full battery, poor light, shading, blown fuse, loose connection, incorrect controller settings, battery-management restriction or a damaged panel.
Start by checking the controller status, battery voltage and whether it detects solar-panel voltage.
Why does my solar controller show zero watts?
The battery may be full, the available light may be too weak, the controller may not detect the panel or charging may have been disabled.
Check the controller’s status or error message rather than relying only on the wattage figure.
Why does the controller show panel voltage but no charge current?
Possible reasons include:
- Battery already full
- Battery not properly connected
- Blown battery-side fuse
- Lithium BMS restriction
- Incorrect battery settings
- Controller disabled
- PV voltage insufficiently above battery voltage
Why does my solar controller show night mode during the day?
The controller may not be receiving enough panel voltage.
Possible causes include heavy shade, poor weather, disconnected wiring, reversed polarity, panel damage or a loose roof connector.
Does a solar panel charge on a cloudy day?
Yes, but output may be much lower than in direct sunlight.
The amount depends on cloud conditions, panel size, orientation, shading and the controller.
Why does solar output drop when the battery is nearly full?
The charge controller reduces current as the battery approaches its target charging voltage.
This is normal and helps prevent overcharging.
Can a blown fuse stop the solar controller working?
Yes.
A blown battery-side fuse can remove the controller’s battery connection, while protection or a disconnection on the panel side can remove its solar input.
Can a lithium battery refuse solar charging?
Yes.
Its BMS may prevent charging because of low temperature, high temperature, excessive voltage, full charge or another protection condition.
Why does the battery still go flat when the solar panel works?
The daily electrical use may exceed the solar energy being generated.
The battery could also be worn, the monitor inaccurate or another charging source may have failed.
Can one shaded panel stop all my solar charging?
It depends on the number of panels and how they are connected.
A shaded or faulty panel can have a larger effect in some series-connected systems than in a parallel arrangement.
Can WeConvert test a solar system installed by someone else?
Yes, subject to access and the condition of the installation.
We can inspect suitable factory-built, professionally converted and self-build campervan or motorhome systems at our Blackburn workshop.
Book Solar Fault Finding in Blackburn
If your campervan or motorhome solar panels are not charging the leisure battery, send us:
- Vehicle make, model and year
- Number and rating of solar panels
- Charge-controller make and model
- Leisure-battery type and capacity
- Screenshots of the controller or app
- Battery-monitor readings
- Any error codes
- Photographs of the panel and roof layout
- Details of recent electrical or roof work
- Whether the system charges from hook-up or while driving
- Your postcode
We can then advise whether to book the vehicle into our Blackburn workshop for solar diagnosis, repair or upgrade.
Contact WeConvert to request campervan or motorhome solar fault finding in Blackburn.