A separate inverter feed
Keep the inverter on its own heavy DC branch while solar charging and cabin lights share the same battery.
Follow the circuit
01
Keep the heavy branch short
The inverter has its own positive and return cables. It does not draw power through the lighting branch or the solar controller's load terminals.
02
Count the shared feeder
The battery-to-bus cables also carry inverter current. Increasing only the final inverter cables leaves the common feeder unchanged.
03
Separate cable protection from the inverter fuse
The battery-end fuse protects the cable leaving the battery. The inverter's internal fuse has a different job and does not replace that decision.
The source and this example
Victron's Phoenix VE.Direct manual documents the battery connections and cable requirements for its 800 VA inverter.
We show the legacy 12/800 DC feed, small solar circuit and central ground bond. AC distribution, neutral bonding and the cabin earth electrode need a separate site design.
- Victron Phoenix VE.Direct 250–1200 VA manual ↗
Battery connection section and model-specific cable table.
- Victron off-grid system grounding diagram ↗
Section 7.7: battery-negative and inverter-chassis connections to the central ground.
Before you build
- Confirm the exact inverter generation: 800 VA / 650 W here, not the newer 800 W model.
- Check surge demand, battery discharge capability, fuse behaviour and actual cable lengths.
- Design the AC protection, earthing and neutral arrangement separately before connecting appliances.
This is a planning example. Cable sizing uses Crimp’s ABYC-based method; the drawing does not certify an installation.
Cable sizes and connections · 14 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 | 2.5 mm²AWG 13 | 15 A | 20 A | 0.88% |
| C6 · Victron MPPT 75/15 BATT − → Negative Bus Bar 3 − | 1 m | 2.5 mm²AWG 13 | 15 A | — | 0.88% |
| C7 · 200 Ah AGM bank + → Positive Bus Bar + | 60 cm | 25 mm²AWG 4 | 62 A | — | 0.22% |
| C8 · 200 Ah AGM bank − → Negative Bus Bar − | 60 cm | 25 mm²AWG 4 | 62 A | — | 0.22% |
| 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% |
| C11 · Positive Bus Bar 3 + → Victron Phoenix Inverter 12/800 DC + | 80 cm | 25 mm²AWG 4 | 60 A | 100 A | 0.28% |
| C12 · Victron Phoenix Inverter 12/800 DC − → Negative Bus Bar 1 − | 80 cm | 25 mm²AWG 4 | 60 A | — | 0.28% |
| C13 · Victron Phoenix Inverter 12/800 Chassis PE − → Cabin earth connection 1 − | 1 m | 16 mm²AWG 6 | 0 A | — | 0.00% |
| C14 · Cabin earth connection − → 200 Ah AGM bank − | 30 cm | 25 mm²AWG 4 | 0 A | — | 0.00% |
A dash means no fuse is assigned to that conductor; upstream protection may apply. Recheck the exact device, holder and placement after edits.
Equipment · 9 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.
- 200 Ah AGM bank
12 V · 200 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.
- Victron Phoenix Inverter 12/800
60 A load allowance · 650 W
Legacy Phoenix 12/800: 800 VA / 650 W model. Dedicated DC branch; AC distribution and neutral bonding are outside this drawing. The chassis ground and battery-negative bond follow Wiring Unlimited section 7.7; the cabin earth electrode still needs site design. Battery-end fuse is an example cable-protection choice, not the internal inverter fuse.
- Cabin earth connection
Central grounding connection per Victron Wiring Unlimited section 7.7. Earth electrode, PV frame bonding and AC protection require the site-specific installation design.
Crimp checks · 2 findings 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: 200 Ah AGM bank
- info: Check inverter disconnection
More off-grid cabin examples
View all five →Solar lighting for a small cabin
Follow one solar panel through a controller and battery to a separately fused lighting circuit.
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.
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