I’ve installed solar on four vans now. The first installation took me 11 hours, involved three trips to the hardware shop for parts I’d forgotten, and resulted in a small roof leak that took two days to discover. The fourth installation took 6 hours start to finish with zero leaks and perfect cable management.

The difference? Understanding where the difficult bits actually are, having the right tools ready, and knowing which steps you absolutely cannot skip (spoiler: it’s the ones involving sealant and testing).

Here’s what nobody tells you: drilling holes in your van roof is genuinely nerve-wracking the first time. You’ll second-guess yourself constantly. That’s normal. But if you follow proper procedures, use correct sealant, and test everything before final assembly, it’s actually difficult to cock it up badly.

I’ve made every mistake you can make: forgotten to prime bolt holes (rust developed), used bathroom silicone instead of marine sealant (failed after 8 months), didn’t test before sealing (had to reopen everything), and mounted panels in stupid locations (shade from roof vent). Learnt from my failures.

This is a complete, step-by-step guide to installing campervan solar system: the planning nobody does properly, the tools you actually need, the techniques that prevent leaks, and the testing procedures that catch problems before they’re sealed forever.

---

Table of Contents

1. Planning Your Installation
2. Tools and Materials
3. Pre-Installation Testing
4. Roof Preparation
5. Panel Mounting
6. Cable Entry and Routing
7. Controller Installation
8. Battery Connections
9. System Testing
10. Troubleshooting
11. Maintenance

---

Planning Your Installation

Don’t skip this. Seriously. I’ve watched people start drilling before measuring properly. It always ends badly.

Step 1: Measure Your Roof Space

You’ll need:

• Tape measure
• Paper and pencil
• Masking tape

Process:

1. Measure total roof dimensions (length × width)
2. Mark obstacles with masking tape:
   • Roof vents (measure their footprint)
   • Roof rack mounting points
   • Antenna mounts
   • Anything protruding from roof
3. Identify curved areas (edges where roof curves down). These are unusable for rigid panels.
4. Measure usable flat area remaining after obstacles
5. Draw to scale on paper (1:20 scale works well)
   • Example: 1cm on paper = 20cm on roof

My van example (VW Transporter):

• Total roof: 4.9m × 1.9m
• Roof vents: Two vents (60cm × 50cm each)
• Roof bars: Four mounting points
• Curved edges: ~25cm around perimeter
• Usable area: 6.8m² approximately

Step 2: Plan Panel Layout

Cut paper rectangles to scale representing your panels.

Standard 100W panel: ~120cm × 55cm Standard 150W panel: ~150cm × 67cm

Considerations:

1. Shadow mapping: Will roof vent cast shadow? At what times of year? Low winter sun creates longer shadows—stand back and visualize sun angles.
2. Cable routing: Panels need to connect. Plan which panels wire together and where cables run.
3. Cable entry point: Where do cables enter van? Near which panel? This determines layout.
4. Access for maintenance: Can you reach all junction boxes for future maintenance?
5. Airflow: Leave some gaps between panels and roof (mounting brackets provide this).

My layout (2× 100W panels):

• Both panels landscape orientation
• 10cm gap between panels (cable routing)
• Positioned to minimize shade from front roof vent
• Cable entry through rear roof vent
• Junction boxes face inward (accessible from gap)

I spent 2 hours playing with paper rectangles. This prevented mounting panels in locations that would’ve been shaded or had difficult cable routing.

Step 3: Mark Panel Positions

Once layout is finalized:

1. Transfer measurements to roof using masking tape
   • Mark panel corners
   • Mark mounting bracket positions
   • Mark cable routing paths
2. Double-check shadows in late afternoon (low sun angle simulates winter)
3. Verify roof vent clearance (measure twice)
4. Check mounting bracket positions don’t hit roof structure
   • Feel underneath headliner
   • Ensure brackets mount to solid roof, not just skin
5. Take photos of marked layout (reference during installation)

Step 4: Identify Cable Entry Point

Three main options:

Option A: Through existing roof vent

• Advantages: No new holes, easy routing
• Disadvantages: Limited by vent location
• Best for: Most people

Option B: New cable gland

• Advantages: Place cables wherever needed
• Disadvantages: Extra hole to drill and seal
• Best for: Professional installations or when vent routing impossible

Option C: Through existing penetrations (antenna holes, etc.)

• Advantages: No new holes
• Disadvantages: Limited locations, may require removing fixtures
• Best for: Specific circumstances

I use Option A (through roof vent). It’s the easiest and least risky method.

Step 5: Plan Wiring Route Inside Van

Before you start:

1. Trace path from cable entry to controller location
   • How do cables run?
   • Through walls? Along roof liner?
   • Behind panels?
2. Measure cable length needed
   • Actual route length (not straight line)
   • Add 1m extra for connections and mistakes
   • Round up to next whole metre
3. Plan controller location
   • Near battery (minimize high-current cable runs)
   • Accessible for monitoring
   • Protected from moisture
   • Visible if controller has display
4. Plan battery location (if not already installed)
   • Low in van (weight distribution)
   • Ventilated space (especially lead-acid)
   • Accessible for maintenance
   • Protected from damage

My setup:

• Cables enter through rear roof vent
• Run along roof liner edge (hidden)
• Drop down rear wall behind furniture
• Controller mounted on rear wall
• 0.5m cable run from controller to battery
• Total cable run: 6m from panels to controller

Safety Planning

Before touching tools:

1. Check weather forecast (dry day for installation—moisture kills sealant adhesion)
2. Plan for leaks (have tarp ready if weather turns)
3. Disconnect battery during electrical work (prevents shorts)
4. Have fire extinguisher accessible (lithium battery safety)
5. Work with someone if possible (passing tools to roof, safety spotter)

---

Tools and Materials

Here’s what you actually need. I’ve listed essentials vs nice-to-have.

Essential Tools

Drilling and mounting:

• Cordless drill (12V+ minimum, 18V better)
• Drill bit set: 2mm, 3mm, pilot sizes, final bolt sizes (6mm, 8mm typical)
• Step drill bit (optional but brilliant for clean holes)
• Deburring tool or round file
• Tape measure
• Spirit level
• Pencil/marker
• Masking tape
• Centre punch (marks drill locations accurately)

Electrical:

• Wire strippers (essential for clean cable prep)
• Crimping tool (for cable terminals)
• Soldering iron + solder (optional, but I prefer soldered connections)
• Multimeter (absolutely essential for testing)
• Screwdrivers (Phillips and flathead, various sizes)
• Spanner set (for bolt tightening)
• Cable cutters (for thick solar cable)

Sealant application:

• Sealant gun (for Sikaflex tubes)
• Disposable gloves (sealant is sticky and difficult to clean)
• Paper towels/rags
• Isopropyl alcohol (90%+, for cleaning)
• White spirit (for cleaning uncured Sikaflex)

Essential Materials

Mounting hardware:

• Mounting brackets (depends on panel and mounting method)
• Stainless steel bolts (M6 or M8 typical, 30-40mm length)
• Stainless steel washers (large diameter for load spreading)
• Stainless steel nylock nuts (prevent loosening from vibration)
• Backing plates (aluminum or stainless, for inside roof)

Sealant:

• Sikaflex 252 or 521UV (proper marine sealant, £15-20 per tube)
• NOT bathroom silicone (will fail)
• NOT cheap sealant (will fail)
• Buy 2-3 tubes (you’ll use more than expected)

Cables:

• Solar cable: 4-6mm² for most systems (buy 10-20% extra)
• Battery cable: 16-25mm² for controller to battery (high current)
• Cable glands (if drilling new holes)
• MC4 connectors (for panel connections)
• Cable ties (UV-resistant)
• Heat shrink tubing (various sizes)

Electrical:

• Inline fuses + holders (solar: 15-20A, battery: 30-60A depending on system)
• Cable lugs (for battery connections)
• Junction box (if splitting solar array)

Protection:

• Primer (rust prevention for drilled holes)
• Touch-up paint (match van color)
• Cable sleeve/loom (protects cables from chafing)

Nice-to-Have Tools

• Torque wrench (proper bolt tensioning)
• Right-angle drill attachment (tight spaces)
• Inspection mirror (see behind panels)
• Endoscope camera (check roof structure before drilling)
• Cable tracer (for routing inside walls)

What I Actually Use

My essential toolkit:

• DeWalt 18V drill (overkill, but I own it)
• Basic drill bit set
• Step drill bit (makes clean holes easily)
• Klein wire strippers
• Engineer PA-09 crimping tool
• Fluke multimeter (cheaper ones are fine)
• Wera screwdriver set
• Sikaflex 252 (3 tubes for complete installation)
• Standard socket set

Total tool cost (if buying new): £150-250 If you own basic tools already: £50-80 for solar-specific items

---

Pre-Installation Testing

Test everything before mounting. I learned this the hard way.

Test 1: Panel Output Verification

Before mounting panels:

1. Connect multimeter to panel output
   • Red probe to positive (usually marked red wire)
   • Black probe to negative (usually black wire)
   • Set meter to DC voltage
2. Measure open-circuit voltage (Voc)
   • In bright sunlight
   • Panel disconnected from everything
   • Should read 18-22V for “12V” panel (this is normal)
   • Should read 36-44V for two 100W panels in series
3. Check current output
   • Set meter to DC amps (10A+ range)
   • Connect meter in series with panel and a load (or short circuit briefly)
   • Should read close to panel rating (5-6A for 100W panel)
   • Do this quickly (under 5 seconds—sustained short circuit can damage cells)
4. Verify polarity
   • Positive should be positive
   • Negative should be negative
   • Mark with tape if not clearly labeled

If panels don’t produce expected voltage/current:

• Check in full sun (not cloudy)
• Ensure panel isn’t shaded at all
• Verify multimeter is working (test on known voltage)
• If still wrong, panel may be faulty (return before installation)

Test 2: Controller Function Test

Before mounting controller:

1. Connect controller to battery
   • Follow polarity carefully (wrong polarity kills controllers)
   • Use appropriate cable size (see controller manual)
   • Include inline fuse on positive cable
2. Controller should power up
   • Display lights up (if it has display)
   • LEDs indicate status
   • No error codes
3. Connect panel to controller
   • Verify correct polarity
   • Controller should detect panel voltage
   • Should show “charging” or “waiting” status
4. Monitor charging current
   • Should show amps flowing to battery
   • Verify current matches expectations (panel rating minus losses)

If controller doesn’t work:

• Verify battery voltage (should be 11-14V for 12V system)
• Check all connections are tight
• Verify fuses aren’t blown
• Check polarity (triple check)
• Consult controller manual troubleshooting section

Test 3: Cable Continuity Test

For each cable before installation:

1. Set multimeter to continuity mode (beep setting)
2. Touch probes to both ends of same conductor
3. Should beep (indicating continuous circuit)
4. Test both positive and negative
5. Test for shorts between positive and negative (should NOT beep)

This catches damaged cables before installation. I’ve had cables with internal breaks that looked fine externally—continuity testing found them.

---

Roof Preparation

This is critical. Surface prep determines whether your installation lasts 2 months or 20 years.

Step 1: Clean Roof Thoroughly

You need:

• Degreaser or strong detergent
• Scrubbing brush
• Hose or buckets of water
• Isopropyl alcohol 90%+
• Clean rags/cloths

Process:

1. Wash entire roof with degreaser
   • Remove all dirt, dust, debris
   • Pay attention to mounting areas
   • Rinse thoroughly
2. Dry completely
   • Chamois or microfiber cloths
   • Ensure no water remains
   • Wait 1-2 hours in sun if necessary
3. Final clean with isopropyl alcohol
   • Wipe mounting areas only
   • This removes any remaining oils/residues
   • Let evaporate completely (2-3 minutes)

Critical: Don’t install if roof is damp. Sealant won’t adhere properly. I’ve had sealant fail because I rushed this step—installed same day as washing. Bad move.

Step 2: Mark Hole Locations

Transfer your planned layout to roof:

1. Place brackets in planned positions
2. Mark mounting holes with pencil
   • Through bracket holes
   • Mark center of each hole clearly
   • Double-check measurements
3. Verify positions with tape measure
   • Check distances match plan
   • Ensure brackets are square
   • Confirm clearance from roof furniture
4. Use centre punch to mark hole centers
   • Creates small dimple
   • Prevents drill bit wandering
   • Mark all holes before drilling any

Step 3: Verify No Obstructions

Before drilling, check underneath:

1. Feel inside van at marked locations
   • Is there solid roof structure?
   • Any wiring/pipes in the way?
   • Enough space for backing plates?
2. Use endoscope camera if available
   • Check roof structure
   • Identify any hidden obstacles
   • Confirm thickness of roof material
3. Check for double-skinned areas
   • Some vans have double-layer roofs
   • Mark if you’ll drill through two layers
   • May need longer bolts

My mistake: Drilled into double-layer roof with too-short bolts. Had to buy longer bolts and redrill slightly offset. Check first.

Step 4: Prepare Paint/Primer

You’ll need:

• Rust-preventative primer (Rustoleum or similar)
• Touch-up paint matching van color (optional)
• Small brush

Have these ready before drilling. You want to prime holes immediately after drilling to prevent rust starting.

---

Panel Mounting

This is where you commit. Deep breath. You’ve planned properly. It’ll be fine.

Step 1: Drill Pilot Holes

Start small:

1. Select 2-3mm drill bit
2. Drill first pilot hole
   • Start perpendicular to surface
   • Drill slowly at first (prevents bit wandering)
   • Feel for any changes in resistance (might indicate hitting structure)
   • Drill through completely
3. Check from inside
   • Verify hole is where expected
   • Ensure no damage to interior
   • Confirm spacing
4. If first hole is good, drill remaining pilots

Why pilot holes?

• Easier to correct mistakes (small holes are easier to seal than large ones)
• Prevents bit wandering on final drilling
• Lets you verify positioning before committing

Step 2: Drill Final Holes

Enlarge to bolt size:

1. Select correct size bit for your bolts
   • M6 bolts: 6.5mm hole
   • M8 bolts: 8.5mm hole
   • Slightly oversized allows bolt insertion
2. Drill slowly
   • Let drill do the work
   • Don’t force it
   • Keep bit perpendicular
3. Deburr holes immediately
   • Use deburring tool or round file
   • Remove sharp edges (prevents cable damage and corrosion)
   • Both inside and outside

Step drill bit alternative:

• Creates cleaner holes with less effort
• Self-deburrs as it cuts
• More expensive (£15-25) but worth it
• I use step bits for all roof drilling now

Step 3: Prime and Seal Holes

Immediately after drilling:

1. Blow out metal shavings (compressed air or breath)
2. Apply rust-preventative primer to bare metal
   • Inside hole edges
   • Let dry 5-10 minutes
   • Essential for preventing rust
3. Optional: touch-up paint on exterior
   • Matches van appearance
   • Additional rust protection
   • Purely cosmetic but nice

I learned this the hard way. Didn’t prime bolt holes on first installation. After 10 months, visible rust around bolts. Had to remove panels, clean rust, reprime, reinstall.

Step 4: Apply Sealant to Brackets

This is critical:

1. Put on disposable gloves (Sikaflex is sticky)
2. Apply sealant to bracket underside
   • Continuous bead around perimeter
   • Cover all edges
   • Don’t skimp (excess will squeeze out—this is good)
3. Apply sealant to bolt threads
   • Each bolt gets coating
   • This seals bolt shaft
   • Prevents water wicking down threads

Sikaflex 252 vs 521UV:

• 252: General marine sealant, excellent adhesion
• 521UV: Better UV resistance, same adhesion
• Both work excellently
• I use 252 (slightly cheaper)

Step 5: Mount Brackets

Work quickly (Sikaflex skins over in 10-30 minutes):

1. Position bracket over holes
2. Insert bolts from outside
   • Through bracket
   • Through roof
   • Sealant on threads will seal as you insert
3. Inside van: add backing plate
   • Spreads load
   • Prevents roof crushing
   • Large washer works if no backing plate
4. Add washer and nylock nut
5. Tighten bolts
   • Snug, not crushing
   • Excess sealant should squeeze out (good sign)
   • Uniform tightness on all bolts

Tightening sequence (for 4-bolt bracket):

• Tighten opposite corners first (1, then 3, then 2, then 4)
• This prevents bracket warping
• Final tighten in same sequence

Step 6: Clean Excess Sealant

While still wet:

1. Remove excess squeezed-out sealant
   • Paper towel for bulk
   • White spirit on rag for cleanup
   • Don’t remove all—leave slight bead at edges
2. Clean bolt heads and bracket surfaces
3. Inspect seal
   • Should be continuous around bracket
   • No gaps
   • Slight bead of sealant visible

Let cure 24-48 hours before mounting panels or driving. Sikaflex needs time to cure fully.

Step 7: Mount Panels to Brackets

After sealant has cured:

1. Position panel on brackets
   • Usually 4 bolts per panel (one per corner)
   • Align mounting holes
2. Insert bolts with washers
   • Stainless steel bolts
   • Washers prevent crushing panel frame
   • Spring washers prevent loosening
3. Tighten bolts
   • Snug, not excessive
   • Panels should be secure but not deformed
   • Check tightness periodically (vibration can loosen)

Panel orientation:

• Junction box accessible (for future maintenance)
• Cable routing direction considered
• Frame mounting holes aligned with brackets

---

Cable Entry and Routing

This determines how clean your installation looks and functions.

Method 1: Through Roof Vent (Recommended)

My preferred method:

1. Remove roof vent assembly
   • Usually 4-6 screws
   • Carefully lift out
   • Note how it reassembles
2. Identify cable routing path
   • Down vent housing
   • Or along edge of vent opening
   • Avoid moving parts (vent mechanism)
3. Drill small hole for cables
   • In vent housing or frame
   • 12-16mm hole for typical solar cables
   • Deburr thoroughly
4. Install cable gland
   • Proper watertight gland (£5-8)
   • Seal with small amount of Sikaflex
   • Tighten compression fitting
5. Route cables through gland
6. Reinstall roof vent
   • Check seal is intact
   • Test vent operation
   • Verify cables don’t interfere

Method 2: New Cable Gland

If vent routing isn’t feasible:

1. Select location for gland
   • Near panels
   • Accessible from inside
   • Solid roof structure
2. Drill hole (size depends on gland)
   • Usually 12-20mm
   • Deburr carefully
3. Prime hole (rust prevention)
4. Install cable gland
   • Apply Sikaflex to gland base
   • Insert from outside
   • Secure inside with nut
   • Tighten compression fitting around cables

Cable glands: Buy proper marine/automotive rated glands. Cheap ones leak.

Panel Wiring on Roof

Series connection (my setup):

1. Connect panel 1 positive to panel 2 negative
   • Use MC4 connectors (solar panels usually come with them)
   • Simply plug together
   • Verify connection is secure
2. Run remaining wires to cable entry
   • Panel 1 negative = array negative
   • Panel 2 positive = array positive
   • These run to controller

Parallel connection:

1. Use junction box on roof
   • All positives connect together
   • All negatives connect together
   • Weatherproof box essential
2. Single cable pair runs from junction box to controller

Cable Routing Inside Van

Best practices:

1. Use cable loom or sleeve
   • Protects cables from chafing
   • Professional appearance
   • UV protection
2. Secure every 30-50cm
   • UV-resistant cable ties
   • Avoid sharp bends (radius > 10× cable diameter)
   • Keep away from hot surfaces
3. Label cables
   • “Solar Positive”, “Solar Negative”
   • Future you will thank present you
4. Avoid high-traffic areas
   • Don’t route under carpets or panels that flex
   • Keep away from water sources
   • Protect from physical damage

My routing (VW Transporter):

• Entry through rear roof vent
• Along roof liner edge (behind trim)
• Down rear pillar (behind plastic panel)
• To controller on rear wall
• Total length: 6m

---

Controller Installation

Where you put the controller matters.

Choosing Controller Location

Ideal location:

• Near battery (minimize high-current cable length)
• Dry area (protected from moisture)
• Accessible for monitoring
• Visible if controller has display
• Ventilated (controllers generate heat)

My location: Rear wall of van, 0.8m from battery, protected by furniture.

Mounting Controller

Most controllers have mounting holes:

1. Mark mounting holes on wall
   • Use spirit level (controller should be level)
   • Mark with pencil
   • Verify clearance for cables
2. Drill pilot holes
   • Appropriate for your wall material
   • Wood: 2-3mm pilot
   • Metal: 3-4mm pilot
3. Mount controller with screws
   • Stainless steel screws
   • Washers for load spreading
   • Ensure controller is secure

Cable access:

• Cables enter from bottom (prevents drips entering controller)
• Leave slack for future service
• Don’t over-tighten cable glands (if controller has them)

Wiring Controller to Solar Panels

Always connect battery BEFORE solar panels (prevents voltage spike damage).

1. Route solar cables to controller
2. Strip cable ends (10-15mm of insulation)
3. Insert into controller solar terminals
   • Usually marked “SOLAR+” and “SOLAR-“
   • Polarity is critical (verify with multimeter if unsure)
   • Tighten terminal screws securely
4. Verify connection
   • Gentle tug test (should not pull out)
   • Check no bare wire exposed outside terminal

Installing Solar Fuse

Fuse goes on positive cable between panels and controller:

1. Calculate fuse rating
   • Panel short-circuit current × 1.25 = fuse rating
   • Example: 6A panel current × 1.25 = 7.5A, use 10A fuse
2. Install inline fuse holder
   • Within 30cm of panel connection
   • Accessible (you may need to replace fuse)
   • Waterproof fuse holder for roof installations
3. Insert fuse
   • Correct rating
   • Quality fuse (not cheap glass fuses that vibrate and break)

My setup: 15A blade fuse in waterproof holder, 20cm from cable entry point.

---

Battery Connections

High current connections. Take care here.

Safety First

Before connecting:

1. Verify all connections upstream are correct
   • Solar panels connected properly
   • Controller wired correctly
   • Fuses in place
2. Double-check polarity (wrong polarity damages controllers and batteries)
3. Disconnect any loads from battery temporarily
4. Wear eye protection (battery connections can spark)

Battery Cable Sizing

Controller to battery requires thick cable:

• 200W system: 16mm² cable minimum
• 300W system: 25mm² cable
• 400W+ system: 35mm² cable

Why so thick?

Solar controllers can deliver 30-60A to batteries (MPPT controllers especially). Thin cables overheat and drop voltage.

My setup: 200W system, 25mm² cable (0.5m run from controller to battery). Overkill but safe.

Cable Preparation

1. Cut cables to length (measure actual route, add 0.5m slack)
2. Strip 15mm insulation from ends
3. Crimp cable lugs
   • Use proper crimping tool
   • Crimp is permanent (should be impossible to pull off)
   • Use correct size lug for cable
4. Heat shrink over connection
   • Seals moisture out
   • Professional appearance
   • Apply heat evenly
5. Label cables
   • “Solar Controller Positive”
   • “Solar Controller Negative”

Battery Fusing

Essential safety feature:

Fuse on positive cable:

• Between controller and battery
• Within 30cm of battery positive terminal
• Rating: 1.25× maximum controller current

Example: 30A controller × 1.25 = 37.5A, use 40A fuse

Fuse types:

• ANL fuse (best for high current)
• MIDI fuse (common in automotive)
• Blade fuse (okay for <30A)

I use ANL fuses (£3-5) with proper holders (£8-12). Rock solid.

Connecting to Battery

Connection sequence:

1. Connect negative cable FIRST
   • Attach to battery negative terminal
   • Tighten securely
   • No spark (negative is safer to connect first)
2. Connect positive cable LAST
   • Through fuse holder
   • To battery positive terminal
   • May spark slightly (normal)
   • Tighten securely

Why this sequence? If you drop a tool while connecting positive-first, it can short to ground. Connecting negative first makes this less likely to cause problems.

Controller Configuration

After battery connected:

1. Controller should power up
   • Display lights (if it has one)
   • LEDs indicate status
2. Configure battery type
   • Lithium, AGM, Gel, Flooded lead-acid
   • Incorrect setting damages batteries
   • Refer to battery manufacturer specs
3. Set charging voltages (if controller allows)
   • Bulk/absorption voltage
   • Float voltage
   • Some controllers have presets (easier)
4. Connect solar panels (final step)
   • Controller should detect panel voltage
   • Begin charging if battery isn’t full
   • Monitor current flow

---

System Testing

Don’t skip this. Testing catches problems while they’re still easy to fix.

Test 1: Voltage Verification

With multimeter:

1. Measure battery voltage
   • Should be 12.4-14.6V (12V system)
   • Note exact voltage
2. Measure solar panel voltage
   • At controller solar terminals
   • Should be 18-22V per panel (varies by series/parallel)
   • In full sun
3. Verify controller display matches multimeter
   • Within 0.1-0.2V is acceptable
   • Large discrepancies indicate issues

Test 2: Current Flow Test

On sunny day:

1. Check controller display for charging current
   • Should show amps flowing to battery
   • Should approach panel rating in full sun
   • Example: 2× 100W panels = ~10-11A in series
2. Monitor for 30 minutes
   • Current should be stable
   • May vary with clouds
   • No sudden drops to zero (would indicate fault)
3. Check battery voltage rise
   • Should increase gradually
   • Example: 12.4V → 12.8V over 1-2 hours
   • Indicates charging is working

Test 3: Load Test

Verify system powers loads:

1. Connect typical load (lights, fridge, etc.)
2. Monitor battery voltage
   • Should drop slightly under load (normal)
   • Should stabilize
   • Solar should reduce voltage drop (charging while under load)
3. Verify controller manages charging correctly
   • Doesn’t shut off under load
   • Maintains appropriate charging

Test 4: Shade Test

Check for wiring issues:

1. Shade one panel completely (cardboard over panel)
2. Monitor system response
   • Current should drop (expected)
   • Should not drop to zero (would indicate series wiring issue)
   • Should continue charging from unshaded panel (parallel only)
3. Remove shade, check recovery
   • Current should return to normal
   • Immediate response

Test 5: Overnight Monitor

Let system run overnight:

1. Note battery voltage at sunset
2. Check again at sunrise
   • Voltage should have dropped slightly (self-discharge and loads)
   • Controller should start charging when sun rises
   • Monitoring ensures controller sleeps/wakes correctly

Test 6: Leak Check

Critical after installation:

1. Wait for heavy rain (or use hose)
2. Check inside van around all mounting points
   • Feel for moisture
   • Look for water stains
   • Check immediately after rain
3. Inspect panel mounting bolts
   • Should be dry
   • No water pooling
   • Sealant should be intact

If leaks found:

• Don’t panic
• Identify exact entry point
• Remove bolt/bracket
• Clean old sealant
• Reapply fresh Sikaflex
• Reinstall

I found a small leak after first installation (bathroom silicone failed). Fixed with proper Sikaflex. No issues since.

---

Troubleshooting

Common problems and solutions.

Problem: No Charging Current

Symptoms:

• Controller shows 0A charging
• Battery voltage not rising
• Panels producing voltage but no current flow

Causes & Solutions:

1. Battery already fully charged
   • Solution: This is normal. Wait until battery discharges slightly.
   • Check: Battery voltage >14.4V = full, won’t accept charge
2. Panel not in sun
   • Solution: Wait for sunny conditions
   • Check: Panel voltage should be 18-22V per panel in sun
3. Faulty connection
   • Solution: Check all connections are tight
   • Wiggle wires while monitoring (loose connection will cause current fluctuation)
4. Blown fuse
   • Solution: Check solar fuse, replace if blown
   • Investigate what caused fuse to blow
5. Controller fault
   • Solution: Check controller display for error codes
   • Consult manual for troubleshooting

Problem: Low Charging Current

Symptoms:

• Charging, but much less than expected
• Example: 200W system producing 3-4A instead of 10-11A

Causes & Solutions:

1. Cloudy weather
   • Solution: This is normal. Expect 20-60% output on cloudy days
   • No fix needed
2. Shading
   • Solution: Reposition van to avoid shade
   • Even partial shade dramatically reduces output
3. Wrong wiring configuration
   • Solution: Verify series/parallel wiring matches controller setup
   • Check polarity
4. Dirty panels
   • Solution: Clean panels with water and soft cloth
   • Dust/dirt reduces output 10-20%
5. Hot panels
   • Solution: This is normal in summer
   • Panels lose ~10% efficiency when hot
   • No fix, just accept it
6. Cable voltage drop
   • Solution: Measure voltage at panels vs controller
   • Should be <0.3V difference
   • If higher, cables too thin or too long

Problem: Controller Error Codes

Common errors:

“Battery overvoltage”

• Cause: Charging voltage too high
• Solution: Adjust controller settings for battery type
• Check: Battery type setting correct?

“Battery undervoltage”

• Cause: Battery deeply discharged
• Solution: Charge battery from mains/alternator first
• Controller may not charge from very low voltage

“PV overvoltage”

• Cause: Solar panel voltage exceeds controller rating
• Solution: Check series wiring (too many panels in series?)
• Verify controller rated for panel voltage

“PV reverse polarity”

• Cause: Solar panel wires backwards
• Solution: Disconnect immediately, swap wires
• Check for controller damage (may need replacement)

“Temperature”

• Cause: Controller overheating
• Solution: Improve ventilation
• Reduce load or move controller to cooler location

Problem: Fluctuating Current

Symptoms:

• Current reading jumps around
• Not stable
• Varies second-to-second

Causes & Solutions:

1. Clouds passing
   • Solution: This is normal
   • Clouds vary panel output rapidly
   • No fix needed
2. Loose connection
   • Solution: Check and tighten all connections
   • Wiggle test each connection while monitoring
3. Faulty panel
   • Solution: Test each panel individually
   • Replace faulty panel
4. Controller MPPT tracking
   • Solution: Some fluctuation normal as MPPT seeks maximum power
   • If excessive (>20% variation in stable sun), controller may be faulty

Problem: Battery Not Reaching 100%

Symptoms:

• Battery charges to 90-95% then stops
• Never fully charged

Causes & Solutions:

1. Insufficient solar
   • Solution: Battery uses more power than solar generates
   • Reduce consumption or add more solar
2. Short charging time
   • Solution: Battery needs 4-6 hours of good sun to fully charge
   • Park in sun longer
3. Wrong absorption voltage
   • Solution: Check controller settings match battery requirements
   • Lithium typically needs 14.2-14.6V absorption
4. Battery degraded
   • Solution: Old batteries lose capacity
   • Test with load tester
   • May need replacement

Problem: Roof Leak

Symptoms:

• Water inside van after rain
• Wet around mounting bolts
• Staining on ceiling

Solutions:

1. Identify exact leak point
   • Feel around all bolts during/after rain
   • May need to remove interior panels to access
2. Remove bolt and bracket
   • Note orientation for reinstall
   • Let area dry completely
3. Clean old sealant
   • Remove all traces
   • Clean with isopropyl alcohol
4. Reapply Sikaflex 252
   • Generous amount
   • On bracket underside
   • On bolt threads
5. Reinstall and let cure 48 hours
   • Don’t drive until fully cured
   • Monitor after next rain

Prevention: Use proper marine sealant (Sikaflex), not bathroom silicone.

---

Maintenance

Solar systems are low-maintenance, but not no-maintenance.

Monthly Checks

5 minutes, once a month:

1. Clean panels if dusty/dirty
   • Water and soft cloth
   • Don’t use abrasive cleaners
   • Morning or evening (not hot panels)
2. Check mounting bolts for tightness
   • Vibration can loosen bolts over time
   • Quick visual and tactile check
3. Inspect cables for damage
   • Look for chafing, cuts, damage
   • Check UV damage on cable jacket
   • Resecure loose cables
4. Verify charging is working
   • Check controller display
   • Confirm current flow on sunny day

Annual Checks

30 minutes, once per year:

1. Deep clean panels
   • Remove accumulated grime
   • Check for physical damage (cracks, delamination)
2. Inspect all sealant
   • Look for cracks, gaps, or degradation
   • Reapply if necessary
   • Check bolt areas especially
3. Check connections
   • Tighten all electrical connections
   • Look for corrosion (green/white deposits)
   • Clean terminals if needed
4. Test full system
   • Verify charging current matches expectations
   • Check battery charging to 100%
   • Confirm controller settings haven’t changed
5. Inspect interior cable routing
   • Check for chafing where cables pass through holes
   • Verify cable ties are secure
   • Look for moisture ingress around cable entry

Long-Term Maintenance

Every 2-3 years:

1. Reseal mounting points
   • Sealant degrades over time
   • Remove bolts, clean, reapply fresh sealant
   • Preventative maintenance
2. Replace worn cables
   • UV degrades cable jackets
   • If cracking or brittleness visible, replace
3. Update controller firmware (if applicable)
   • Victron and some other brands offer updates
   • Improves performance and fixes bugs

Panel Cleaning Tips

Do:

• Clean with water and soft cloth
• Clean in morning/evening (cool panels)
• Use long brush for hard-to-reach panels
• Dry after cleaning (prevents water spots)

Don’t:

• Use abrasive cleaners (scratches glass)
• Clean hot panels (can crack from thermal shock)
• Use pressure washer (can damage seals)
• Walk on panels (will crack cells)

---

Final Thoughts

My first solar installation took 11 hours, involved two trips to buy forgotten parts, and resulted in a small leak that took a week to notice. My most recent installation took 6 hours with zero issues.

The difference? I learned that solar installation isn’t difficult—it’s methodical. The people who struggle are the ones who skip planning, rush through sealant application, or forget to test before sealing everything permanently.

If you take away one thing from this guide: test everything before making it permanent. Connect panels before mounting. Wire controller before sealing cables. Check for leaks before calling the job done. Problems found early are easy fixes. Problems found after everything’s sealed are expensive nightmares.

The most common mistake isn’t technical—it’s rushing. Take your time. Do proper surface prep. Use correct sealant. Test thoroughly. Your future self will thank you when the installation works flawlessly for years.

And please, use proper marine sealant. The £15 you save using bathroom silicone will cost you hours of remedial work when it fails after 6-12 months. Sikaflex 252 is expensive because it actually works. I’ve learned this the expensive way so you don’t have to.

My 200W system has been flawless for 22 months. Zero leaks, zero failures, zero regrets. It took 7 hours to install including multiple test cycles and proper sealant curing time. That 7 hours has saved me hundreds of hours of hookup dependency and given me freedom to camp anywhere.

Now go install some solar panels on your van, and actually read the Sikaflex application instructions before squeezing the trigger.

---

Where to Buy (UK Sources)

Solar panels:

• Amazon UK (wide selection)
• Renogy UK (www.renogy.com/uk)
• 12V Planet (www.12vplanet.co.uk)
• Bimble Solar (www.bimblesolar.com)

Controllers:

• Amazon UK (EPEver, Renogy)
• 12V Planet (premium brands)
• Victron dealers (victronenergy.co.uk)

Mounting hardware:

• Renogy UK (complete kits)
• Amazon UK (generic brackets)
• Van conversion specialists

Sealant (critical):

• Sikaflex 252: Marine chandleries, eBay, Amazon
• Sikaflex 521UV: Same sources
• Don’t buy from hardware shops (they stock bathroom silicone, not marine sealant)

Cables:

• 12V Planet (quality solar cable)
• Vehicle wiring specialists
• Amazon UK (verify specifications)

Tools:

• Screwfix (drills, tools)
• Toolstation (similar to Screwfix)
• Amazon UK (specialized tools)