Kimberley Kamper solar panel failures

The lifespan of the factory fitted solar panel on Kimberley Kampers has proven to be unacceptably short. 

Even though we did not supply Kimberley Kamper with solar products we have received many phone calls and emails from Kimberley Kamper owners trying to find a solution.  Our investigation has found a number of factors that cause the failures.

 

The cause of solar panel failures on Kimberley Kampers

Brief overview:

The solar panel lifespan on Kimberley Kampers is short because of excessive thermo-mechanical stress at the cells and interconnects which gradually fracture lowering panel output; ultimately the fractures worsen becoming a complete open circuit with zero output from the panel.  

The cause of this is:

  • a mix of the thermo-mechanical relationships between roof, panel and the attachment between the two; and
  • the wiring of the panels.

As the roof cannot be changed, the problem needs to be fixed by a combination of the following:

  • using more robust solar panels;
  • using a different attachment method; and
  • wiring the panels differently.
 

Resolving short lifespan of solar panels on Kimberley Kampers

 

Main Issue

 

ISSUE 1 - Temperature/thermal cycling: Different materials have different expansion coefficients.

 

Cause of the problem

As materials heat up and cool down it creates stress at the interfaces between the materials.  The cells expand the least followed by the copper, so any expansion of the roof creates a stretching stress on the cells and interconnects.   Note that the plastic layers in the panel also expand, but they are not stiff like the roof so cannot apply any significant force on the cells and interconnects.

Avoiding/Fixing the problem
  • Reduce maximum temperature and temperature variations – this is significantly improved by the vented gap.
  • Use materials with low thermal expansion coefficient.

 

Manufacturing/Quality Issues

 

ISSUE 2Half cells used in 55W panels: Half cells have only one inter-connection between cells and not three as in the case of full cells.

 

Cause of the problem

Stress (stretching forces) at the interconnects emanating from the longitudinal thermal expansion of the panel have to be absorbed by a single interconnect between the SunPower cells and not shared (divided) between 3 interconnects as in the full cell panels. Ie. With only one connection between each half-cell it needs to solely absorb the stretching forces which are created by the expansion of the roof.  

Avoiding/Fixing the problem
  • Use only solar panels with full A grade SunPower cells.  Large solar panels with half cells is not an option.
  • With three connections on full cells, the force is dispersed over all three connections which decreases the stress on each connection.

 

ISSUE 3Cell quality: There are a large number of grades (quality) of cells and poor quality cells may have been used.

 

Cause of the problem

There is a huge price difference between high and low grade cells (very evident on eBay).  Visually they can look the same.  Low(er) grade cells are cut into smaller cells.

Avoiding/Fixing the problem
  • Using genuine SunPower cells
  • The manufacturer must be able to confirm the grade of the cells used.  Read our buyer guide here 
 

ISSUE 4 - solar panel backsheet: Backsheet with high thermal expansion and low tensile strength

 

Cause of the problem

High expanding, low tensile strength backsheets create and transmit more stress to the cells and interconnects, thereby reducing the lifespan of the panel.  Manufacturers are driven by price and not lifespan of the panels they make.  It’s a case of “buyer beware”, but this is very difficult as a consumer is not normally aware of the issues around the backsheet and it is virtually impossible even for a knowledgeable person to tell the difference between backsheet materials when the panel is new.

Avoiding/Fixing the problem
  • With solar panels price is a good indicator of quality - you get what you pay for.
  • Solar 4 RVs is very precise in our specifications to our manufacturer ensuring the best materials available for each component of the solar panel.  This costs more but we do not compromise on quality.

 

Installation site Issues

 

ISSUE 5 - Roof material: Fibreglass thermal expansion is problematic

 

Cause of the problem

Virtually all fibreglass campers, caravans etc use polyester resin because it is the lowest cost of the resins available (it’s perfectly fine for its primary purpose), but the problem is it has the highest thermal expansion coefficient of the resins.  Expansion is reduced by the glass fibre, but we know that some roofs still expand too much and will destroy panels bonded to the roof.

Avoiding/Fixing the problem
  • Panels on fibreglass must have an adequate vented gap between the panel and the roof.
  • Using a very high bond double-sided tape rather than an adhesive such as silicon or polyurethane

 

ISSUE 6 - High temperature: Solar panels on insulated surface get extremely hot

 

Cause of the problem

The higher the temperature, the higher the stress, the higher the failure rate.  

Avoiding/Fixing the problem
  • A vented gap is required between the panel and roof.  This can reduce the panel temperature by up to around 15-20°C and even lower for the roof.  
  • Spacers can be used

 

ISSUE 7 - Roof material breakdown: Fibreglass can weaken or break down

 

Cause of the problem

Fibreglass is stressed by high temperature and moisture which can result in yellowing/browning and fractures in the surface which then allows moisture to penetrate into the fibres.  This can lead to the fibreglass weakening and losing some of its dimensional stability and expanding which further stresses the solar panel.

Avoiding/Fixing the problem

Panels on fibreglass must have an adequate vented gap between the panel and the roof.  This will stop moisture and heat being trapped.

 

Wiring Issues

 

ISSUE 8 - Wiring of cells/panels and by-pass diodes

 

Cause of the problem

This is very complex.  It looks like there has been a variety of cell/panel arrangements, some of which may cause additional heating of SunPower cells under partial shading.

Avoiding the complexity behind all this; ideally there should be 32 SunPower cell strings wired to one MPPT charge controller, with multiples of these as needed.   To minimise cost of multiple controllers/regulators the 32 cell strings can be wired in parallel into one controller.  

Avoiding/Fixing the problem
  • Use 30 - 36 cell strings.  To optimise harvest use one controller per string; otherwise strings comprising the same number of cells can be wired in parallel into a single controller. 
  • No other wiring arrangement is appropriate.

 

ISSUE 9 - Tabs under panel: Tabs location vary with different batches of Kimberley solar panels 

 

Cause of the problem

Different solar panel manufacturers/batches have tabs in different locations.  There appears to be many wiring variations between different Kimberley Kampers which means the cable roof entry point is not consistent.  Replacement solar panels are unlikely to match-up exactly with the current cable entry hole.

Avoiding/Fixing the problem

The need for a vented gap allows cables to be routed under the panel and through the existing holes (images are show later in this guide).

 

Other Issues

 

ISSUE 10 - Exposure to the elements: Constant UV exposure shortens the life of lightweight solar panels

 

Cause of the problem

Lifespan of panel is primarily determined by length of time spent exposed to the sun.  A van used 2 months of the year and covered 10 months will extend panel lifespan by 6x.

Avoiding/Fixing the problem
  • 1. Extend solar panel longevity by covering panels when power not needed 
  • 2. Solar 4 RVs RADpower brand lightweight solar panels have a top layer of ETFE – Read about the benefits of ETFE here 

 

Providing a solar power solution to Kimberley Kampers owners

 

Solar 4 RVs has ordered a specific manufacturing run of their RADpower brand solar panels with SunPower GEN III MAXEON cells and an ETFE top layer to suit kimberley Kampers.

These higher grade 110W and 55W lightweight panels will have a junction box on the underside of the panel.

The panels will be provided with a kit so they can be installed with a vented gap between the panel and roof.

 

Solar panel arrangement

The image below shows the arrangement proposed that suits most Kimberley Kamper owners.  Some Kimberley Kamper owners may require a different layout.

 

Kimberley Kamper solar panel layout

 

Roof top panels

By using 2 x 110W panels to replace the existing 3 x 55W panels the output will be increased from 165W to 220W.  The overall footprint dimensions (space utilised) will still be exactly the same.

 

replacing Kimberley Kamper failed solar panels

 

Lobster Tail panels

1 x 110W is proposed to replace the existing 2 x 55W. 

The overall footprint dimensions will be less as shown below.

 

Fixing Kimberley Kamper Lobster tail solar panel failures

 

Sloping side panels (not rear)

The combination of using full cells plus a vented gap means that the sloping sides are not quite wide enough to accommodate a 3-cell width panel.  Therefore 2 x 8 cell panels are suggested for the sides.  These are rated 55W  – the power generated in sunny conditions will be higher than the existing 55W watt panels due to the panel being cooler because of the vented gap under. 

The two panels will be wired in series gives 32 cells in series which is the same as the 110W panels on the roof.  

 
Sloping rear panel

A 2 x 8 cell panel can be fitted here, however the voltage of the 16 cells is insufficient at 9V for a conventional charge controller. 

If this panel is going to be used then a Genasun boost solar charge controller will be needed.

It cannot be placed in series or parallel with any of the other panels. 

 

The panels are on order and will be put on our website when they are available.  A link to the products will be provided on this page hopefully in late November / early december.

 

What is ETFERADpower SunPower cell lightweight solar panel with textured robust ETFE top layer

The solar panel's top clear layer is made of ETFE (Ethylene-Tetra-Fluoro-Ethylene) which is a high-strength fluorine polymer that is corrosion and stain resistant, non-stick self-cleaning, has high light transmittance, and boasts long service life. 


It will not discolour or degrade from exposure to environmental pollution, UV light, harsh chemicals or extreme temperature variations.  The surface is textured for extra robustness.