Solar, Batteries & Power Systems for Boats and Campervans: A Buyer's & Installation Guide
Whether you are fitting out a campervan for long weekends or keeping the lights, fridge and instruments running on a boat at anchor, the principles are the same. This guide walks through how the four core components fit together, how to size them for your usage, and what to look out for during installation.
At Galway Maritime we supply and support both Victron Energy and Mastervolt equipment — two of the most trusted names in marine and mobile power. Victron's BlueSolar and SmartSolar range covers panels, MPPT charge controllers, inverters and lithium batteries, while Mastervolt's ChargeMaster and EasyCharge units are proven shore-power and onboard chargers.
The products linked throughout this guide are a small sample of what we stock — many more sizes, models and accessories are available. If you are unsure what suits your boat or van, talk to us before you buy.
1. How an Off-Grid 12V / 24V System Fits Together
Every onboard or campervan power system is built from the same core blocks. On a boat especially, the strength is in how they work together — Victron has built marine systems on this approach for over 50 years:
- Solar panels — convert daylight into DC current. Sized in watts (W).
- Charge controller (MPPT) — regulates panel output, charging the battery safely and harvesting the most power.
- Battery bank — stores energy for use after dark or under cloud. Sized in amp-hours (Ah) or kilowatt-hours (kWh).
- Inverter / inverter-charger — converts stored DC into 230V mains for appliances; an inverter/charger also recharges from shore power.
Most boats and vans add one or more top-up charging sources for when solar falls short — a shore-power or onboard charger (Mastervolt ChargeMaster or EasyCharge, or a Victron MultiPlus), a DC-DC charger to charge the house bank from the engine alternator while underway, and sometimes a generator. A system monitor such as the Victron Cerbo GX or all-in-one Ekrano GX — or simply the free VictronConnect app over Bluetooth — ties everything together and lets you see what's coming in and going out.
2. Step One: Work Out Your Energy Budget
What's a watt-hour? A watt-hour (Wh) is just a unit of energy — how much power a device uses multiplied by how long it runs. The sum is simple: watts × hours = watt-hours. A 5-watt LED cabin light left on for 4 hours uses 20Wh. Do that for everything aboard, add it up, and you have your daily energy budget.
Working in amps? Most boat and van gear is rated in amps at 12 volts. To turn amps into watts, multiply by the voltage: watts = amps × volts. So a water pump pulling 5A at 12V draws 60W — run it for half an hour and that's 30Wh.
And amp-hours? Batteries are often rated in amp-hours (Ah). At 12V, multiply Ah by 12 to get watt-hours — so a 100Ah battery holds roughly 1,200Wh. That's the bridge between how batteries are sold and how your usage is measured.
🔌 Daily Usage Estimator — tap to open or close
Set how many of each item you have and roughly how many hours a day you use it. We've pre-filled typical values for a small cruiser — adjust to suit. High-power 230V items only run for minutes, so enter a small fraction of an hour (0.1h ≈ 6 minutes).
⚡ Power System Sizing Calculator
Recommends real Victron components and a buildable battery bank. Indicative only — contact us to confirm a final specification.
The calculator assumes around 2.5 peak-sun-hours (conservative for the west of Ireland) and typical system losses. You can safely oversize the solar array — the MPPT caps at its rated output — handy for winter. For an exact cold-weather voltage check on your chosen panels, use Victron's MPPT calculator.
3. Solar Panels
GenerateSolar is the workhorse of any off-grid system — silent, maintenance-free and your only "free" source of power once installed. Victron's BlueSolar panel range covers both monocrystalline rigid panels and slimline options to suit different mounting situations.
Choosing between panel types:
- Rigid / framed panels: highest efficiency and lifespan. Best for campervan roofs with a mounting frame, or boats with a dedicated arch, bimini or pushpit rail.
- Flexible / semi-flexible panels: lightweight and low-profile, can follow a gentle curve and be bonded directly to a surface. Slightly lower output and shorter life, but ideal where weight or windage matters.
Mounting notes: On a boat, keep panels clear of boom, sail and rigging shadow where possible — even partial shading sharply reduces output. On a campervan, leave an air gap beneath rigid panels for cooling, and seal all roof penetrations properly. Wire panels back to the controller with adequately-sized cable to minimise voltage drop.
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Price range: €45.95 through €116.95Select options This product has multiple variants. The options may be chosen on the product page
4. Charge Controllers (MPPT)
RegulateA solar charge controller protects your battery from over-charging and squeezes the most energy out of your panels. There are two technologies: PWM (basic, low cost) and MPPT (Maximum Power Point Tracking). For any system you care about, MPPT is the right choice.
Victron's MPPT range — the BlueSolar and Bluetooth-enabled SmartSolar controllers — are highly efficient, automatically detect 12V or 24V battery voltage, and use adaptive multi-stage charging tuned to your battery type. Smaller models connect by VE.Direct; larger models add a VE.Can port for bigger arrays. On a boat, splitting a large array across multiple MPPT controllers also helps manage shading from rig and superstructure.
Sizing rule: divide your total panel wattage by your battery voltage to find the minimum charge current — for example, 400W at 12V needs at least a 30A controller. Check the panel open-circuit voltage stays within the controller's PV input limit, and leave headroom. Victron's free online MPPT calculator (victronenergy.com/mppt-calculator) matches panels to the right controller.
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Price range: €59.95 through €146.95Select options This product has multiple variants. The options may be chosen on the product page
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Price range: €32.50 through €62.95Select options This product has multiple variants. The options may be chosen on the product page
5. Batteries
StoreYour battery bank is the heart of the system. Capacity is measured in amp-hours (Ah) or kilowatt-hours (kWh), but the figure that really matters is usable capacity, which depends on the chemistry — and on whether the battery is built for deep cycling or for starting.
- Lithium (LiFePO₄): ~80% usable depth of discharge, thousands of cycles, fast charging and light weight. Victron's Lithium Battery Smart range, or the all-in-one Lithium SuperPack with built-in management. Best value over the life of the install.
- AGM: sealed, maintenance-free lead-acid with low internal resistance — good for high-draw loads. Limited to ~50% usable capacity for good life.
- GEL: sealed, with excellent deep-cycle tolerance and vibration resistance; suits slower, gentler discharge.
- Deep-cycle leisure (flooded): rugged, cost-effective house batteries for caravans, motorhomes and boats — such as the Ampac marine & leisure range we keep in store.
- Dual-purpose & starting (flooded): high cranking power plus useful capacity — for engine starting and lighter house duty. We stock the DN Automotive M31-950 (below). Not intended for heavy daily cycling.
Two numbers worth knowing. Cold Cranking Amps (CCA) is how much punch a battery delivers to start an engine in the cold — the higher the better for a starter battery. Reserve Capacity is roughly how many minutes it can run house loads before it's flat. A starting battery has big CCA; a house battery prioritises capacity and deep-cycle life. A dual-purpose battery aims to do both.
Managing a lithium bank. Victron lithium batteries are designed to run with a battery management system — a Lynx Smart BMS or VE.Bus BMS controls charging and protects the cells. Pair it with a Smart BatteryProtect to stop DC loads accidentally over-discharging the battery, and the system looks after itself.
We don't list our marine batteries online — including the Ampac leisure range and DN Automotive dual-purpose batteries like the M31-950 — but we keep them in stock and are happy to advise on the right type and capacity for your boat or van. Call in or get in touch for current sizes and pricing.
Enquire About Batteries6. Inverters & Inverter/Chargers
DeliverIf you only run 12V/24V loads — LED lights, water pump, USB charging, a compressor fridge — you may not need an inverter at all. Add one when you want to run 230V appliances such as a kettle, microwave, induction hob or power tools.
- Standalone inverter (e.g. Victron Phoenix): converts DC to AC. Choose a pure sine wave model for sensitive electronics — Victron's deliver roughly twice their continuous rating in short bursts, for trouble-free motor and pump start-up.
- Inverter/charger (e.g. Victron MultiPlus, or Quattro): combines an inverter, a powerful battery charger and an automatic mains transfer switch in one unit, and works as a UPS. Mastervolt also offer combined units for marine installations.
MultiPlus or Quattro? The MultiPlus handles one AC input (shore power). The Quattro accepts two AC inputs — for example shore power and a generator — and switches automatically to whichever is live. Both feature PowerControl (keeps the AC draw below your set shore/generator limit) and PowerAssist (instantly tops up an above-limit demand from the battery), so you won't trip a shore-side fuse or overload a generator — meaning you can often run a smaller generator and save weight.
Sizing: match the continuous rating to your largest expected load and check the peak/surge rating for motors and pumps. A 1,200–2,000VA unit covers most campervans; liveaboard boats often step up to 3,000VA. Victron units can be paralleled or set up in split/three-phase to scale from around 500VA right up to very large banks if your needs grow.
7. Shore-Power, Alternator & Onboard Charging
Top UpShore-power and onboard chargers. Whenever 230V is available, a dedicated charger brings the batteries back to full quickly and correctly:
- Mastervolt ChargeMaster Plus: professional automatic charger in outputs such as 12V/35A, 12V/50A, 24V/20A and 24V/30A, with multiple isolated outputs to charge engine-start and service banks together.
- Mastervolt EasyCharge: compact, weather-resistant fixed-mount chargers (6A and 10A) for smaller boats, charging flooded, GEL and AGM batteries.
- Victron inverter/charger: if you fit a MultiPlus you already have a powerful charger built in (see the previous section).
Charging from your engine (DC-DC). While you motor, a DC-DC charger lets the engine alternator top up your service battery without flattening the starter battery. Victron's Orion XS and Orion-Tr Smart DC-DC chargers (isolated and non-isolated versions) take the alternator's variable output and deliver a stable, correct charge to a 12V or 24V house bank — including lithium. For high-output smart alternators, a Smart BuckBoost converter accepts a wide input range and prevents alternator overload. This is one of the most useful upgrades for any cruising boat or touring campervan.
Match a charger's output current to your bank — roughly 10–25% of the bank's Ah capacity is a sensible rate — and confirm it suits your battery chemistry, especially if you've moved to lithium.
8. Installation, Wiring & Monitoring
Safety CriticalA safe, reliable install comes down to a handful of fundamentals:
- Fusing & distribution: fit an appropriately-rated fuse or breaker in every positive conductor, as close to the battery as practical. A tidy, modular DC busbar and fuse system such as Victron's Lynx Power In and Lynx Distributor keeps a larger install safe and serviceable.
- Cable sizing: size cables for the current and run length to keep voltage drop low. High-current runs (battery to inverter, battery to charger) need substantial cable.
- Temperature-compensated charging: connect the temperature sensor supplied with Victron chargers and inverter/chargers; solar chargers then share that data automatically.
- Mounting: keep electronics dry, ventilated and away from heat, with airflow around inverters and chargers.
Monitoring. Knowing what your system is doing is what makes it reliable. Options range from a phone to a full glass-bridge dashboard:
- VictronConnect app — connects over Bluetooth to SmartSolar controllers, smart batteries and more, to check and configure from your phone.
- Battery monitor (SmartShunt or BMV-712 Smart) — shows state of charge, time-to-go and charge/discharge current, with alarms for excessive discharge.
- GX device — the Cerbo GX with a GX Touch 50/70 display, or the all-in-one waterproof Ekrano GX, gives full local control and remote monitoring through Victron's VRM portal (a GlobalLink 520 adds cellular VRM where there's no Wi-Fi).
- Chartplotter integration (boats): via a GX device and the Victron Marine MFD app, your power system can appear right on a compatible multi-function display from the major chartplotter brands — battery state of charge, shore/generator status, tank levels and more on one screen.
9. Two Example System Builds
Weekend campervan (~1,000 Wh/day, 12V):
- 300–400W of roof-mounted solar feeding a Victron SmartSolar MPPT (30A class).
- 100–150Ah of 12.8V lithium for two to three nights off-grid.
- A 1,200–1,600VA inverter (or MultiPlus inverter/charger if you use campsite hook-ups).
- VictronConnect on your phone for monitoring.
Coastal cruising boat (~2,500 Wh/day, 12V or 24V):
- 400–600W of solar across the arch or coachroof, on one or more MPPT controllers to manage shading.
- 300Ah+ of lithium service bank, sized for your fridge and electronics.
- A Victron MultiPlus inverter/charger for shore-power changeover, plus a Mastervolt ChargeMaster Plus where a dedicated multi-output charger suits the layout.
- A Cerbo GX system monitor for full local and remote oversight.
These are sample configurations using a small selection of our range — we stock many more sizes and models, and can tailor a system to your exact boat or van.
10. Safety, Legal & Regulatory Notes (Ireland)
Mains power is deadly230V AC mains (campervans and boats). In the Republic of Ireland, fixed electrical installations are governed by IS 10101:2020, the National Rules for Electrical Installations (which explicitly covers caravans). The 230V side of your installation — shore-power inlet, consumer unit, mains sockets and any inverter mains output — should be designed, installed and certified by a qualified electrician (a Registered Electrical Contractor under the Safe Electric scheme) working to IS 10101:2020. An RCD and an accessible means of isolation/disconnection must be fitted on the AC side.
DC wiring and fusing. Low-voltage DC work (12V/24V solar, batteries and charge controllers) is not a controlled electrical work, but it must still be installed correctly. Fit an appropriately-rated fuse or breaker in every positive conductor, as close to the battery as practical, and size all cable for the current and run length. A short circuit on a high-current DC system is a serious fire risk.
Lithium batteries. Use lithium (LiFePO₄) batteries with an integral or external Battery Management System (BMS), install them in a ventilated location, and make sure every charging source uses a lithium-appropriate charge profile. Do not charge lithium below freezing unless the battery has built-in low-temperature protection. Damaged cells can pose a fire risk.
Boats — Recreational Craft Directive. New recreational craft between 2.5 m and 24 m placed on the EU market must comply with the Recreational Craft Directive (2013/53/EU), with electrical work to EN ISO 13297. Retrofits to existing boats should follow the same standard as best practice. Be aware that significant modifications to a CE-marked boat can affect its conformity. Commercial fishing vessels are covered separately by the Code of Practice.
Solar panels. A single solar module can generate a DC voltage over 30 V in direct sunlight even when not connected, which is potentially hazardous. Never disconnect panels under load, do not disassemble modules, and follow all local, regional and national regulations. Installation should be carried out by qualified persons.
- Gas and combustion appliances (LPG, diesel heaters) are outside the scope of this guide and have their own regulations — have them fitted and checked by a registered installer.
- Insurance and warranty: a poor or undocumented installation may invalidate insurance or void product warranties. Keep records and use correctly-rated components.
- Always follow each manufacturer's manual for connection, polarity, fusing and torque settings.
Not Sure What You Need? Talk to the Galway Maritime Team
Choosing and sizing a power system is easier with someone who fits them every day. We supply and support the full Victron Energy and Mastervolt ranges for boats and campervans — backed by Victron's 50+ years of marine know-how, a worldwide network of authorised dealers and up to a 5-year warranty on many products. The items shown throughout this guide are just a sample of what we hold.
Tell us your daily usage and how you use your boat or van, and we'll spec the panels, controller, batteries, inverter, charger and alternator charging to match — and help arrange installation if you need it.
Get In TouchFrequently Asked Questions
The questions we're asked most often when helping boat owners and campervan builders choose a power system.
Do I legally need an electrician to install my system?
The 12V/24V DC side — solar panels, charge controller and batteries — is extra-low voltage and can be installed by a competent person, provided every positive cable is correctly fused and all cabling is properly sized. The 230V AC side is different: the shore-power inlet, any consumer unit, mains sockets and an inverter's mains output should be designed, installed and certified by a qualified electrician working to Ireland's IS 10101:2020 wiring rules, and must include RCD protection. If you're not confident, we can help arrange installation.
MPPT or PWM — does it really matter?
For any system you rely on, yes — choose MPPT. Victron's SmartSolar and BlueSolar MPPT controllers are up to around 30% more efficient than a basic PWM unit and charge your battery correctly through every stage. PWM only makes sense for tiny trickle-charge setups.
Lithium or AGM — which should I choose?
For regular off-grid use, lithium (LiFePO₄) wins — about 80% usable capacity, far more charge cycles, lighter weight and faster charging. AGM/GEL is cheaper up front but limited to roughly 50% usable capacity and a shorter life if cycled hard every day. Over the life of the install, lithium is usually the better value.
What size solar array and battery do I need?
Start with your daily energy use in watt-hours, then size the battery bank and solar array from that figure. Use the sizing calculator earlier in this guide for a starting specification, then contact us to confirm it for your specific boat or van.
Can I mix Victron and Mastervolt equipment?
Yes. We supply and support both brands and they work happily together — for example a Victron solar, MPPT and battery setup alongside a Mastervolt ChargeMaster shore-power charger. The important thing is that every charging source is set to the correct charge profile for your battery type, which we'll help you get right.
Will solar keep my batteries charged through an Irish winter?
Not on its own. Short, overcast winter days produce only a fraction of summer's harvest. Plan to top up from shore power — a Mastervolt charger or a Victron MultiPlus — or from your engine alternator during the darker months.
Do I actually need an inverter?
Only if you want to run 230V mains appliances such as a kettle, microwave or laptop charger. If everything aboard runs on 12V/24V DC — LED lighting, water pump, compressor fridge, USB charging — you may not need an inverter at all.
Does the Recreational Craft Directive apply to my boat?
New recreational craft between 2.5 m and 24 m placed on the EU market must comply with the Recreational Craft Directive (2013/53/EU), which covers electrical installation and protection; the relevant standard is EN ISO 13297. Retrofitting an existing boat is not directly governed by the Directive, but following ISO 13297 is strongly recommended as best practice. Commercial fishing vessels are covered separately under the Code of Practice.
Could a new system affect my insurance or warranty?
It can. A poor or undocumented installation may invalidate your boat or vehicle insurance, and incorrect wiring can void product warranties. Keep your receipts and documentation, use correctly-rated components, and have the 230V side installed and certified by a qualified electrician.
Can you help me choose the right kit, or install it?
Yes — that's what we're here for. Tell us your daily usage and how you use your boat or van, and we'll specify the panels, controller, batteries, inverter and charger to match, and help arrange installation where you need it.
Disclaimer: This guide is general information only and is current at the time of writing. It is not a substitute for professional design, installation, electrical or legal advice. Regulations and standards change over time — always verify the current requirements before you build. Sizing figures are indicative starting points only. Regulated electrical work should be carried out by a suitably qualified person, and all equipment installed in accordance with the manufacturer's instructions. Galway Maritime accepts no liability for any installation carried out on the basis of this guide.