Solar lighting for a small cabin
Follow one solar panel through a controller and battery to a separately fused lighting circuit.
Follow the circuit
01
Separate charging from lighting
The controller and lights meet at the battery buses. Opening the lighting branch leaves the solar charging path connected.
02
Protect each branch
The terminal fuse protects the battery feeder. A separate 20 A fuse serves the controller; the smaller lighting wire has its own 3 A fuse.
03
Try a longer cable
Open the example and increase both lighting cable lengths. Compare voltage drop before choosing where to put the battery cabinet.
The source and this example
Victron's MPPT connection diagram shows a solar charger, battery and separately fused DC loads.
We use a smaller 75/15 controller, a 175 W panel, a 110 Ah AGM battery and a 2 A lighting allowance. The controller's LOAD terminals are unused.
- Victron MPPT electrical connection diagram ↗
Section 4.6: basic solar, battery and DC-load circuit.
- 75/15 installation and fuse requirements ↗
Before you build
- Check panel cold-weather voltage and select a DC-rated PV disconnect.
- Set the AGM charging profile; connect and verify the battery before connecting PV.
- Cable sizing uses Crimp's marine tables. Building grounding and local wiring requirements need a separate design.
This is a planning example. Cable sizing uses Crimp’s ABYC-based method; the drawing does not certify an installation.
Cable sizes and connections · 10 conductors
Lengths are one way. Sizes and currents come from the same Crimp model as the drawing. Each drop value covers one drawn conductor; the full circuit includes its supply and return. AWG values are approximate counterparts to the metric areas.
| Connection | Length | Wire | Design current | Fuse | Drop |
|---|---|---|---|---|---|
| C1 · Victron 175W Mono + → Solar DP Isolator IN + | 3 m | 2.5 mm²AWG 13 | 9 A | — | 0.98% |
| C2 · Victron 175W Mono − → Solar DP Isolator IN − | 3 m | 2.5 mm²AWG 13 | 9 A | — | 0.98% |
| C3 · Solar DP Isolator OUT + → Victron MPPT 75/15 PV + | 30 cm | 1.5 mm²AWG 16 | 9 A | — | 0.16% |
| C4 · Solar DP Isolator OUT − → Victron MPPT 75/15 PV − | 30 cm | 1.5 mm²AWG 16 | 9 A | — | 0.16% |
| C5 · Victron MPPT 75/15 BATT + → Positive Bus Bar 1 + | 1 m | 4 mm²AWG 11 | 15 A | 20 A | 0.55% |
| C6 · Victron MPPT 75/15 BATT − → Negative Bus Bar 3 − | 1 m | 2.5 mm²AWG 13 | 15 A | — | 0.88% |
| C7 · Victron AGM Deep Cycle 12V/110Ah + → Positive Bus Bar + | 60 cm | 4 mm²AWG 11 | 15 A | — | 0.33% |
| C8 · Victron AGM Deep Cycle 12V/110Ah − → Negative Bus Bar − | 60 cm | 2.5 mm²AWG 13 | 15 A | — | 0.53% |
| C9 · Positive Bus Bar 2 + → Cabin lighting · 2 A + | 3 m | 1.5 mm²AWG 16 | 2 A | 3 A | 0.58% |
| C10 · Cabin lighting · 2 A − → Negative Bus Bar 2 − | 3 m | 1.5 mm²AWG 16 | 2 A | — | 0.58% |
A dash means no fuse is assigned to that conductor; upstream protection may apply. Recheck the exact device, holder and placement after edits.
Equipment · 7 components
- Victron 175W Mono
19.4 V · 9.03 A rated / planning output · 175 W · 23.7 V STC Voc
175W rigid mono panel, 12V nominal (Vmp 19.4V, Voc 23.7V) — works with PWM or MPPT controllers. 1485×668×30mm, 11kg, MC4 connectors.
- Solar DP Isolator
Illustrative two-pole PV disconnect. Select an actual DC-rated device for the array's cold open-circuit voltage and short-circuit current.
- Victron MPPT 75/15
15 A rated / planning output
75/15 battery circuit: 20 A fuse, within Victron's 20–25 A range. The controller's LOAD terminals are unused; the lighting branch is battery-fed.
- Victron AGM Deep Cycle 12V/110Ah
12 V · 110 Ah
40 A terminal fuse is this example's cable-protection choice. Verify the selected fuse, holder and interrupt capacity against the actual battery. Ah does not establish fault current.
- Positive Bus Bar
Positive bus bar — common feed with multiple output studs.
- Cabin lighting · 2 A
2 A load allowance · 24 W
Generic 2 A lighting allowance. Replace it with the actual lamps and hours used before relying on the energy budget.
- Negative Bus Bar
Negative bus bar — common return with multiple output studs.
Crimp checks · 1 finding to review
These are the current engine findings for the saved example. They remain visible when you open it in Crimp.
- warning: Check fuse suitability: AGM 110Ah
More off-grid cabin examples
View all five →Monitor the cabin battery
Add a SmartShunt so both solar charging and cabin lighting pass through the battery monitor.
Protect the cabin battery
Put a BatteryProtect in the lighting branch while leaving the solar charging path available to recover the battery.
Two roof faces, two solar controllers
Give each solar array its own controller, then combine their battery outputs at the cabin's DC buses.
A separate inverter feed
Keep the inverter on its own heavy DC branch while solar charging and cabin lights share the same battery.
Crimp for AI agents · public beta
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