What is the difference between a starter battery and a leisure battery?

A starter (cranking) battery is designed to deliver a very high current for a short time to start the vehicle engine. It is not designed to be deeply discharged. A leisure battery is designed for repeated, slow, deep discharge and recharge cycles — supplying current to lights, water pump, heating controls, and other 12V loads over many hours. Using a starter battery as a leisure battery will shorten its life dramatically. Leisure batteries are typically rated in amp-hours (Ah) for a 20-hour discharge rate.

What type of leisure battery is best for a caravan or motorhome?

Lead-acid leisure batteries are the traditional choice and are available in flooded, sealed (VRLA), and AGM (absorbent glass mat) formats. AGM batteries tolerate deeper discharge and vibration better than flooded lead-acid and are maintenance-free. Lithium iron phosphate (LiFePO4) batteries offer the best performance — deeper discharge (80% vs 50% for lead-acid), lighter weight, longer cycle life, and faster charging — but at a higher initial cost. For motorhomes and caravans used frequently or for extended off-grid periods, lithium batteries often represent better long-term value.

What is an MPPT solar charge controller and why does it matter?

An MPPT (Maximum Power Point Tracking) solar charge controller electronically adjusts the operating point of the solar panel to extract the maximum available power, then converts it to the correct voltage to charge the battery. A PWM (Pulse Width Modulation) controller simply connects the panel to the battery when the panel voltage is sufficient. MPPT controllers typically harvest 10–30% more energy than PWM controllers, especially in partly cloudy conditions or when the panel is not perfectly oriented. For panels rated above 80–100W, MPPT controllers are strongly recommended.

Is a caravan electric hookup connection safe to use?

Yes, provided the hookup cable is in good condition, the site supply is properly installed to BS 7671 Section 708, and the caravan's mains socket inlet is in good condition. Before connecting, visually inspect the EHU cable for cuts, damaged insulation, or a damaged plug. Ensure the cable is fully uncoiled to prevent overheating. The RCD at the caravan park pitch supply unit provides earth fault protection, but the caravan may also have an internal RCD. If the RCD trips on connection, disconnect immediately and investigate before reconnecting.

What is a galvanic isolator and do I need one?

A galvanic isolator is a device fitted in series with the shore power earth conductor that blocks low-level DC galvanic currents while passing AC fault currents safely. Without a galvanic isolator, DC galvanic currents from adjacent boats or caravans connected to the same site earth can flow through the water or ground, causing corrosion of aluminium chassis components, steel frames, and other metalwork over time. A galvanic isolator is strongly recommended for all caravans and motorhomes that regularly use shore power, particularly at marinas. It should comply with BS 8444.

Do I need a pure sine wave inverter?

It depends on what you want to power from it. Modified sine wave (MSW) inverters produce a stepped approximation of a sine wave and are adequate for simple resistive loads (incandescent lights, basic heating elements). However, MSW inverters can cause problems with motor-driven appliances (fridges, fans, air conditioning), sensitive electronics (laptops, medical equipment, CPAP machines), and appliances with complex power supplies. Pure sine wave (PSW) inverters produce a true sine wave output identical to the mains supply and are compatible with all appliances. For a motorhome or caravan, a PSW inverter is almost always the correct choice.

How often should a caravan or motorhome electrical system be checked?

An annual electrical safety check is strongly recommended for all caravans and motorhomes. The check should include: visual inspection of all 12V wiring for chafing, damage, or corrosion; battery condition test (voltage, capacity, and internal resistance); leisure battery charging system check (converter/charger, solar controller); test of the 230V shore power socket and EHU cable condition; RCD functional test on any internal RCD; inspection of the gas and electrical interface for CO detector and smoke alarm function. For leisure vehicles used frequently or for extended periods, more frequent checks may be appropriate.

ELECTRICAL GUIDE

Caravan & Motorhome Electrical Guide UK: 12V & 230V Systems

Everything you need to know about caravan and motorhome electrical systems — leisure batteries, solar charging with MPPT controllers, mains shore power hookup, pure sine wave inverters, 12V DC wiring, shore power safety, and annual maintenance.

Start 7-day free trial

Free for 7 days · No charge until day 8 · Cancel anytime · Used by 1,000+ UK electricians

13 min readUpdated 2026-05-18Andrew Moore, Founder of Elec-Mate

Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.

ShareX in W

1,000+

UK electricians

“Replaced three separate apps with Elec-Mate. Certs, quotes, and scheduling all in one place.”

Daniel Palmer — DP Electrical

Key Takeaways

1Caravans and motorhomes typically have two separate electrical systems: a 12V DC system (powered by the leisure battery) for lighting, water pump, and controls; and a 230V AC mains system powered from shore power (electric hookup, EHU) or an inverter.
2The leisure battery is separate from the vehicle starter battery and is designed for repeated deep discharge. AGM and lithium (LiFePO4) leisure batteries offer advantages over standard lead-acid in terms of depth of discharge and service life.
3Solar panels charge the leisure battery via a solar charge controller (MPPT or PWM). MPPT controllers are more efficient — typically 10–30% more energy harvested — and are recommended for panels rated above 100W.
4Shore power connections use the blue 16A IEC 60309 (CEE) connector. The connection provides 230V AC at up to 3.68 kW for mains appliances on board. A galvanic isolator fitted to the earth conductor protects against galvanic corrosion of metalwork.
5Inverters convert the 12V DC battery supply to 230V AC, allowing mains appliances to be used off-grid. Pure sine wave inverters are required for sensitive electronics and motorised appliances. Modified sine wave inverters are only suitable for simple resistive loads.
6Annual electrical safety checks by a competent person — covering the leisure battery condition, 12V wiring, mains hookup socket and cable, RCD operation, and solar system performance — are strongly recommended.

01 · Electrical Guide

Caravan & Motorhome Electrical Systems: An Overview

Modern caravans and motorhomes contain sophisticated electrical systems that combine 12V DC and 230V AC technology to provide comfort and convenience whether connected to mains shore power or operating off-grid. Understanding how these systems work together is essential for safe and effective use — and for the growing number of electricians who work on leisure vehicle electrical systems.

12V DC system — the backbone of the leisure vehicle electrical system. Powered from the leisure battery, the 12V system supplies internal lighting (typically LED throughout modern vehicles), the water pump, the heating system controls, the fridge (12V compressor or absorption cooling), ventilation fans, and all 12V sockets and USB charging points.
230V AC system — provided when connected to shore power (EHU) or when using an inverter. The 230V system supplies mains socket outlets for appliances such as kettles, microwaves, hairdryers, and laptop chargers. In motorhomes, the 230V system also typically supplies the mains charger (converter) that charges the leisure battery from the EHU.
Charging sources — the leisure battery can be charged from multiple sources: the vehicle's alternator via a battery-to-battery (B2B) charger while driving; a solar panel via a solar charge controller; from the EHU via the mains converter/charger; or from a portable generator via a mains charger. Modern energy management systems (EMS) coordinate these sources automatically.

The internal electrical installation of leisure vehicles is not covered by BS 7671. It is governed by BS EN 1648-1 (touring caravans) and BS EN 1648-2 (motorhomes), which specify the requirements for 12V DC and 230V AC systems within the vehicle. The shore power installation at the caravan park is covered by BS 7671 Section 708.

Free download

Get the BS 7671 A4:2026 Cheat Sheet — free

Every key change in the 2026 amendment on one page. AFDDs, TN-C-S protection, new schedule columns, model forms. Pinned on your van dash.

Every regulation change summarised
New model forms (EIC + MEIWC)
Free PDF — no subscription

02 · Electrical Guide

Leisure Battery Systems

The leisure battery is the heart of the 12V electrical system. Choosing the right battery type, sizing it correctly for your power requirements, and maintaining it properly will determine how many hours of off-grid power you have available.

Lead-acid (flooded) — the traditional leisure battery. Relatively low cost, widely available, and recyclable. Should not be discharged below 50% of capacity (to around 12.0 V under load). Requires periodic topping-up with distilled water if the cell caps are accessible. Produces hydrogen gas during charging — must be used in a ventilated locker.
AGM (Absorbent Glass Mat) — a sealed lead-acid variant where the electrolyte is held in glass fibre mats rather than free liquid. Tolerates deeper discharge (down to 50% recommended, 80% maximum), handles vibration better, requires no maintenance, and can be mounted in any orientation. Higher cost than flooded lead-acid but recommended for motorhomes due to vibration tolerance.
Lithium iron phosphate (LiFePO4) — the premium option. Can be discharged to 80% depth of discharge (compared to 50% for lead-acid) giving effectively 1.6× the usable capacity from the same nominal Ah rating. Significantly lighter, charges faster, and lasts 3–5× as many cycles as lead-acid. Requires a lithium-compatible charger and BMS (battery management system) and cannot be charged below 0°C without a self-heating version.
Battery sizing — calculate daily 12V consumption (sum of each load in amps × hours of use). Double this figure for lead-acid (to stay above 50% depth of discharge) or divide by 0.8 for lithium. The result is the minimum battery capacity in amp-hours required. Add margin for cloudy solar days or reduced alternator charging time.

03 · Electrical Guide

Solar Charging for Caravans and Motorhomes

Solar panels are now almost universal on touring motorhomes and increasingly fitted to static caravans. A well-designed solar system provides free battery charging and extends the time between EHU hookups.

Panel types — monocrystalline panels offer the highest efficiency (typically 20–23%) and are best for roof installations where space is limited. Flexible (thin-film) panels conform to curved roofs but are less efficient (10–15%) and have shorter service lives. Semi-flexible panels (monocrystalline cells on a thin backing) offer a compromise.
MPPT vs. PWM controllers — an MPPT (Maximum Power Point Tracking) solar charge controller extracts maximum power from the panels by electronically optimising the operating point. A PWM controller applies simple pulse-width modulation charging. MPPT controllers are 10–30% more efficient and are recommended for any system with panels rated above 80–100W. MPPT controllers also allow panels with a higher open-circuit voltage than the battery voltage, giving more flexibility in panel selection.
Wiring and cable sizing — solar panel wiring must be rated for the short-circuit current of the panel array (typically 1.25× the rated short-circuit current). Minimise cable length and use appropriately sized cable to limit voltage drop between the panel and the controller. All connections must be weatherproof and suitable for outdoor UV exposure. MC4 connectors are the industry standard for solar panel wiring.

04 · Electrical Guide

Mains Shore Power (Electric Hookup) Connections

Shore power (electric hookup, EHU) provides 230V AC mains electricity to the caravan or motorhome from the site supply. Understanding how the hookup system works and how to use it safely is essential for all leisure vehicle owners.

IEC 60309 (CEE) connectors — shore power uses the blue 16A IEC 60309 connector (the same as at caravan parks and marinas). The blue colour indicates 230V single-phase. The earth pin engages first when connecting and last when disconnecting. EHU cables are typically 10–25 m long and rated at 16A. The cable must not be used above its rated current.
Power limitation — most UK caravan park pitches provide a 16A supply (maximum 3.68 kW). Be aware that running multiple high-load appliances simultaneously (kettle, microwave, fan heater, battery charger) can exceed this limit and trip the pitch RCD or MCB. A caravan energy management system (EMS) automatically disconnects lower-priority loads to prevent overload.
Reverse polarity — some older or poorly maintained sites have reversed polarity on the pitch supply (live and neutral conductors swapped). This is a safety hazard as it means switches in the appliance interrupt the neutral rather than the live. A simple polarity tester plugged in after hookup will detect this immediately. Do not use the supply if reverse polarity is indicated — inform the site office.

05 · Electrical Guide

Inverters: Converting 12V DC to 230V AC

An inverter converts 12V DC battery power to 230V AC, allowing mains appliances to be used when not connected to shore power. Choosing the right type and size of inverter is critical for reliable performance.

Pure sine wave vs. modified sine wave — pure sine wave (PSW) inverters produce a smooth 230V AC output identical to the mains supply. They are compatible with all appliances. Modified sine wave (MSW) inverters produce a stepped approximation that works with simple resistive loads but can damage or fail to operate sensitive electronics, variable-speed motors, and appliances with switched-mode power supplies.
Inverter sizing — the inverter must be rated to handle the peak power demand of all appliances that may be run simultaneously. Inductive loads (motors, compressors) have a startup surge of 2–3× their running power. As a rule, size the inverter at 1.5–2× the expected running load. Allow for inverter efficiency (typically 85–90%) when calculating battery drain.
Inverter-charger (combi units) — a combined inverter-charger automatically switches from inverter mode (off-grid) to charger mode (on EHU) when shore power is connected. This simplifies the system and provides uninterruptible supply transition. Most modern motorhome installations use an inverter-charger as the central power management device.

Try Elec-Mate free for 7 days

16 certificate types, 70+ calculators, RAMS, quoting, invoicing, AI agents, and 46+ training courses — from £6.99/mo.

Start free trial

06 · Electrical Guide

12V DC Systems: Wiring and Components

The 12V DC system is the most complex and varied part of a leisure vehicle's electrical installation. Poor 12V wiring — undersized cables, poor connections, inadequate fusing — is a common cause of fires in caravans and motorhomes.

Cable sizing — 12V DC systems operate at low voltage, which means current is high for a given power load. A 60W load at 12V draws 5A; the same load at 230V draws only 0.26A. All 12V cables must be sized for the maximum current they will carry, accounting for volt drop (typically limited to 0.5V or 4% of 12V in leisure vehicle standards) and for continuous rather than intermittent duty.
Fusing and circuit protection — every 12V circuit must be individually fused or protected by a circuit breaker as close to the battery as practicable. The fuse or circuit breaker rating must not exceed the current rating of the cable it protects. A fuse sized to protect the load rather than the cable is a common and dangerous mistake in DIY 12V installations.
Battery-to-battery (B2B) chargers — a B2B charger (also called a DC-DC charger) efficiently charges the leisure battery from the vehicle's alternator while driving. Unlike a simple split-charge relay, a B2B charger provides a controlled multi-stage charge profile suitable for AGM and lithium batteries without risk of damaging the alternator or starter battery. Essential for lithium battery systems.

07 · Electrical Guide

Shore Power Safety: Key Precautions

Shore power provides a convenient mains supply but introduces electrical hazards that must be managed correctly. These are the most important safety practices for using shore power at caravan parks, campsites, and marinas.

Inspect the EHU cable before use — check the entire cable for cuts, abrasions, or damage to the outer sheath. Check the plug and socket faces for damage, discolouration from heat, or bent pins. A damaged EHU cable must be taken out of service. Do not repair EHU cable insulation with tape — replace the cable.
Check for reverse polarity — use a simple plug-in polarity tester after every hookup connection. Reverse polarity is a fault condition, not a minor inconvenience. It causes switches to interrupt the neutral rather than the live, leaving appliance parts live when they appear switched off. Do not use the supply if reverse polarity is detected.
Do not exceed the pitch current rating — most pitches are rated at 16A (3.68 kW). Running a fan heater (2 kW), a kettle (2 kW), and a microwave (1 kW) simultaneously will trip the pitch supply. Be aware of the total connected load and manage it within the pitch rating.
Galvanic isolator — at marinas and motorhome stopovers where multiple vehicles share a common earth, fit a galvanic isolator to the shore power earth conductor. This protects against galvanic corrosion of chassis metalwork caused by DC currents flowing through the common earth.

08 · Electrical Guide

Electrical Maintenance for Caravans and Motorhomes

Regular electrical maintenance extends the life of the electrical system, prevents failures at inconvenient times, and most importantly maintains safety. These are the key maintenance tasks for caravan and motorhome owners.

Annual Pre-Season Check

Before the first outing of the season, carry out or commission an annual electrical check covering: leisure battery capacity and condition; all 12V connections for corrosion; solar panel output; EHU cable and inlet socket condition; RCD functional test (press the test button — the RCD must trip); smoke detector and CO alarm battery replacement.

Winter Storage Battery Care

Lead-acid leisure batteries must not be left in a discharged state during winter storage — sulphation will permanently reduce capacity. Either keep the battery connected to a maintenance charger throughout winter, or remove the battery and store it on a maintenance charger in a frost-free location. Lithium batteries should be stored at approximately 50% charge in a cool, dry location.

Professional Annual Inspection

An annual professional electrical inspection by a qualified electrician experienced in leisure vehicle electrics provides peace of mind and may be a requirement of some insurance policies. The inspection should cover both the 12V DC and 230V AC systems and result in a written report. Use the Elec-Mate certificate app to generate professional inspection reports on site.

Caravan & motorhome electrical checks made simple with

Join 1,000+ UK electricians using Elec-Mate for on-site inspection reporting, test result recording, and instant PDF export.

Try it free for 7 days

Frequently Asked Questions About Caravan and Motorhome Electrical Systems

What electricians say

Verified reviews from the UK App Store.

One App for Everything!

Elec-Mate is my go to app for business and electrical work. It's feature rich without feeling cluttered. A true all in one app for quotes, certs, calculations, RAMS, EICRs, and more. I use it every day without fail, and it makes my workflow much smoother since I'm not jumping between apps anymore. The price-to-feature ratio is excellent. Any issues I've had, the developer responds within the hour and usually fixes them the same day. 100% recommend.

Fantastic app for electricians

I've used the app and the web based version for a while now and it's well worth the investment. If you're an apprentice or experienced Spark give it a go, you won't be disappointed.

Absolutely amazing

I've been using Elec-Mate for a while now, and honestly, it's one of the best apps I've ever downloaded. Every aspect of it feels thoughtfully designed, from the clean and intuitive interface to the powerful features that make everything so easy to manage. It's clear that a lot of care and attention went into building this app, and it shows in every detail.

Trusted by electricians across the UK

Real feedback from real sparks

“Replaced three separate apps with Elec-Mate. Certs, quotes, and scheduling all in one place.”

Daniel Palmer

Sole Trader · DP Electrical

“I've won two contracts this month because I could turn quotes around same-day with the AI cost engineer.”

Nathan Perry

Electrician · NP Electrical Services

“The study centre got me through my AM2. Mock exams and flashcards are brilliant.”

Jake Pizey

3rd Year Apprentice · Apprentice

7-Day Free Trial — Cancel Anytime, No Hassle

Complete Leisure Vehicle Electrical Inspections on Your Phone

Join 1,000+ UK electricians using Elec-Mate for on-site inspection reporting, test result recording, and instant PDF export. Perfect for caravan and motorhome annual electrical checks. 7-day free trial.

“Replaced three separate apps with Elec-Mate. Certs, quotes, and scheduling all in one place.”

Daniel Palmer, DP Electrical

From £6.99/mo after trial — less than a coffee a week

or download the app

7 days free, then from £6.99/moCancel in one tap — no calls, no hassleiOS, Android & WebBS 7671 compliant

Caravan & Motorhome Electrical Guide UK: 12V & 230V Systems

Key Takeaways

Caravan & Motorhome Electrical Systems: An Overview

Get the BS 7671 A4:2026 Cheat Sheet — free

Leisure Battery Systems

Solar Charging for Caravans and Motorhomes

Mains Shore Power (Electric Hookup) Connections

Inverters: Converting 12V DC to 230V AC

Try Elec-Mate free for 7 days

12V DC Systems: Wiring and Components

Shore Power Safety: Key Precautions

Electrical Maintenance for Caravans and Motorhomes

Annual Pre-Season Check

Winter Storage Battery Care

Professional Annual Inspection

Caravan & motorhome electrical checks made simple with

Frequently Asked Questions About Caravan and Motorhome Electrical Systems

What is the difference between a starter battery and a leisure battery?

What type of leisure battery is best for a caravan or motorhome?

What is an MPPT solar charge controller and why does it matter?

Is a caravan electric hookup connection safe to use?

What is a galvanic isolator and do I need one?

Do I need a pure sine wave inverter?

How often should a caravan or motorhome electrical system be checked?

Continue reading

Caravan Park Electrical (BS 7671 Section 708)

Battery Storage Systems Guide

Solar Panel Installation Guide

EICR Certificate App

What electricians say

One App for Everything!

Fantastic app for electricians

Absolutely amazing

Trusted by electricians across the UK

Complete Leisure Vehicle Electrical Inspections on Your Phone