Two roof faces, two solar controllers
Give each solar array its own controller, then combine their battery outputs at the cabin's DC buses.
Follow the circuit
01
Keep the PV inputs separate
Each panel has a controller and two-pole disconnect. Shade on one roof does not force the other panel into the same series string.
02
Combine after the controllers
The outputs join at the DC buses. Each controller has its own 20 A battery-side fuse; neither controller is wired through the other.
03
Check the combined charge
Both chargers can operate together. Compare their combined output with the battery's charge limit and use matching battery profiles.
The source and this example
Victron's Wiring Unlimited busbar diagrams connect multiple solar chargers to a common battery system.
We reduce the arrangement to two 175 W panels, two 75/15 controllers and one 200 Ah AGM battery. Separate roof faces are an example use case, not a measured installation.
- Victron Wiring Unlimited: large system busbars ↗
Section 4.10: multiple solar chargers connected to shared busbars.
- 75/15 controller installation ↗
Before you build
- Size the shared battery cables for both chargers operating together.
- Check each array's cold voltage and short-circuit current independently.
- The drawing does not simulate roof angle, shade patterns or communication between controllers.
This is a planning example. Cable sizing uses Crimp’s ABYC-based method; the drawing does not certify an installation.
Cable sizes and connections · 16 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 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 3 + | 60 cm | 10 mm²AWG 8 | 30 A | — | 0.26% |
| C8 · 200 Ah AGM bank − → Negative Bus Bar − | 60 cm | 6 mm²AWG 10 | 30 A | — | 0.44% |
| 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 1 − | 3 m | 1.5 mm²AWG 16 | 2 A | — | 0.58% |
| C11 · Second roof · 175 W + → Solar DP Isolator IN + | 3 m | 2.5 mm²AWG 13 | 9 A | — | 0.98% |
| C12 · Second roof · 175 W − → Solar DP Isolator IN − | 3 m | 2.5 mm²AWG 13 | 9 A | — | 0.98% |
| C13 · Solar DP Isolator OUT + → Victron MPPT 75/15 PV + | 30 cm | 1.5 mm²AWG 16 | 9 A | — | 0.16% |
| C14 · Solar DP Isolator OUT − → Victron MPPT 75/15 PV − | 30 cm | 1.5 mm²AWG 16 | 9 A | — | 0.16% |
| C15 · Victron MPPT 75/15 BATT + → Positive Bus Bar 1 + | 1 m | 2.5 mm²AWG 13 | 15 A | 20 A | 0.88% |
| C16 · Victron MPPT 75/15 BATT − → Negative Bus Bar 2 − | 1 m | 2.5 mm²AWG 13 | 15 A | — | 0.88% |
A dash means no fuse is assigned to that conductor; upstream protection may apply. Recheck the exact device, holder and placement after edits.
Equipment · 10 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.
- Second roof · 175 W
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
Double-pole isolator switch — breaks both the positive and negative solar legs simultaneously for safe panel disconnect.
- Victron MPPT 75/15
15 A rated / planning output
Separate PV input; battery outputs share the same bank. Match battery profiles and verify the combined charging limit.
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: 200 Ah AGM bank
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.
A separate inverter feed
Keep the inverter on its own heavy DC branch while solar charging and cabin lights share the same battery.
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