The architecture
Panels mount on a dock roof, pole or nearby sunny bank. The battery/controller live in a ventilated weatherproof locker above flood/splash level. A fused DC bus distributes to lighting, USB-C, 12V socket, small fridge and battery-charging leads.
Load and sizing math
The refrigerator dominates. If you omit it, the same build can shrink to a 50Ah battery and 100–200W panel.
| Load | Watts | Hours/day | Daily Wh | Notes |
|---|---|---|---|---|
| 12V compressor fridge | 35 | 10 | 350 | Duty-cycle equivalent |
| Dock LEDs | 20 | 5 | 100 | Under-rail + task light |
| USB-C / phones | 25 | 2 | 50 | Mixed devices |
| Fish-finder battery charge | 50 | 2 | 100 | After a day on water |
| Illustrative total | 600 Wh/day | Before system margin | ||
Around 600Wh/day is a robust estimate. A 100Ah battery stores ~1.28kWh nominal, giving comfortable overnight reserve. 300W of panel can replenish the day in a few strong sun hours.
Full parts list
This is a shopping architecture, not a demand that you buy one exact brand. Match voltage, current and connectors before ordering. Budget ranges reflect the class of hardware rather than a live quote.
300W solar array
Target spec: Rigid panels on shade roof or pole
Enough energy for refrigeration and charging.
Budget: $160–$400 each
100Ah LiFePO4 battery
Target spec: IP-rated case or protected locker
High cycle life and light weight.
Budget: $150–$300 each
30A MPPT controller
Target spec: LFP profile, Bluetooth optional
Efficient charging and monitoring.
Budget: $80–$180 each
Marine fuse block
Target spec: Tinned-copper, covered, negative bus
Marine hardware tolerates wet/corrosive environments better.
Budget: $30–$80 each
12V compressor fridge
Target spec: 35–55L class
The major convenience load.
Budget: $250–$650 each
Waterproof USB-C / 12V outlets
Target spec: PD USB-C and marine sockets
Charge phones, speakers, lights and boat electronics.
Budget: $20–$70 each
Wiring map
Use tinned copper, adhesive heat-shrink and drip loops. Elevate battery/electronics above expected flood or wave splash.
[300W PV]-->[MPPT]-->[100Ah LFP]-->[MARINE FUSE BLOCK]
| | | |
Fridge LEDs USB-C 12V charge lead
Step-by-step build
Decide whether the dock or shore holds the battery
Shore mounting is easier to keep dry; dock mounting shortens load wiring. Avoid any location that can be submerged.
Mount panels for sun and wind
A roof panel can double as shade, but verify structure and wind uplift.
Install the electrical locker
Mount controller, fuse block and battery with drainage/ventilation appropriate to the hardware.
Use marine-grade cable
Crimp tinned lugs, seal with adhesive heat-shrink and support wire so wave movement does not flex terminals.
Wire fridge and lighting branches
Give the fridge its own fuse and avoid skinny cigarette-lighter extensions.
Add charging outlets
Install USB-C and 12V outlets under cover where plugs are not exposed directly to rain.
Load-test at dusk
Run fridge, all lights and charging at once while watching battery voltage.
Inspect after the first storm
Check water intrusion, cable strain and panel fasteners after real weather.
Commission it before you trust it
The project is not finished when the LED comes on. Run it through a controlled test so the first real failure is not in the field.
- Electronics above flood level
- Marine/tinned cable used
- All penetrations sealed
- Battery restrained
- Fridge voltage drop checked
- Lighting glare aimed away from water navigation
- GFCI used for any AC additions
- Panel wind load checked
- Emergency disconnect labeled
Mistakes to avoid
Undersizing the battery because the panel is large
Panels make energy only when conditions cooperate. The battery has to carry the load through night, cloud and short high-demand events. Size energy storage from watt-hours, not panel watts.
Ignoring standby loads
Controllers, routers, cameras, inverters and cellular hardware can consume power 24/7. On small projects, a 5W always-on device is 120Wh per day—sometimes more than the 'main' load.
Using one fuse for the entire project
Fuse each branch according to its conductor and load. The fuse protects wire, not the gadget. A downstream short should not require an oversized main fuse to clear.
Mounting the panel where the project is instead of where the sun is
The load can sit in shade. The panel cannot. Use a cable run, pole or remote mount to put the collector in the best solar window.
Skipping a low-voltage disconnect
Deep-discharge protection is cheap insurance. Many charge controllers or smart battery systems can disconnect noncritical loads before the battery is abused.
Upgrade path
Add a livewell/aerator circuit
A fused 12V branch can run bait or fish aeration.
Add a small inverter only when necessary
Keep core loads DC; add a switched pure-sine inverter for an occasional AC tool.
Add shore-power charging
A waterproof AC charger can top the battery when utility power is available without changing the solar architecture.
Frequently asked questions
Can I put the battery under the dock?
Not where it can flood or be repeatedly splashed. Keep it above water in a protected enclosure.
Do I need an inverter?
No for the core build; every listed load has a native 12V option.
Will 300W run the fridge year-round?
It depends on climate, shading and fridge duty cycle; measure/estimate winter sun if the dock remains active year-round.
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