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Your guide to buying a leisure battery for your caravan or motorhome

Carlton Boyce / 01 April 2015 ( 24 March 2021 )

An auxiliary, or leisure, battery is a must for anyone taking their caravan, motorhome or campervan on the road while enjoying all the comforts of home.

Retired couple enjoying a motorhome holiday
A leisure battery allows caravan and motorhome users to get off the beaten track and really enjoy life on the road

While you might think the days of the leisure battery are long gone thanks to the widespread availability of EHU (Electric Hook Up) points at almost every campsite, they’re still an essential component if you’re fond of off-the-beaten track, back-to-basics sites - or if your EHU point fails through a fault or a power cut!

What does the leisure battery power?

Your oven ignition, fridge, heater, and internal lights, for example, will all be powered by the battery if you’re not at an EHU-friendly site. Don’t forget that you’ll need to charge your phone, laptops, tablet and camera batteries, too. It’s easy to forget that the world has moved on since we all went camping 20 years ago and the height of electrical sophistication was a battery powered lantern…

And yet, despite their many advantages, not every newly built caravan and motorhome will have one fitted, which is just one more thing to add to the budget if you need to get one installed yourself.

And if your existing outfit doesn’t have one then few upgrades will make such a difference to your quality of life as a decent power source.

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The difference between a car battery and a leisure battery

Car batteries and leisure batteries are very different, so please don’t try to save money by fitting a car battery for caravan power. This is because a car battery is designed to give an instance jolt of big power to start and engine, while a leisure battery is designed to provide a constant, steady power source over a long period. 

But, just like the good old starter battery, a leisure battery’s power is measured in Ah (ampere hours); the greater the Ah, the longer it will last and the fewer times you’ll have to recharge it. 

The downside is that the more power, the bigger the physical size of the battery and the greater the weight – and both are a concern when space is tight and weight-load is an issue.

So, you will need to trade one off against the other, depending on your priorities; emergency and infrequent use will let you get away with buying a smaller, lighter and cheaper battery compared to someone who spends most of their time camping in the wild off the grid.

Read our guide to caravan accessories

The different types of leisure battery available

There are four types of leisure battery in common use: ‘wet’ lead acid batteries; gel batteries; AGM (Absorbed Glass Mat) batteries; and the Enhanced Flooded Battery. All have their pros and cons. 

The traditional ‘wet’ lead acid battery is the best known and use well-proven, straightforward technology. They are the most common type and are usually the cheapest to buy. They are also very simple to maintain but they do have to be fixed securely in an upright position to prevent the acid spilling out - and if it does it will make a dreadful mess.

Gel batteries are liquid-free and so you needn’t worry about acid spillage; though, like all sealed batteries, you must be aware of not overcharging them. They are more expensive than ‘wet’ batteries to buy and so you may have to spend a little bit more to get a suitable on-board charger to prevent overcharging. Like the AGM batteries you will read about in the next paragraph, they can be fitted on their side and are well-suited to applications where they may be jiggled around a lot, such as in off-road vehicles.

AGM, or Absorbent Glass Mat, batteries have become well established as an effective leisure and caravan battery. Overcharging can lead to battery failure and they are more costly to buy than ‘wet’ batteries. However, they are much safer and more environmentally friendly, and can be fitted lying on their side, which helps you to be able to squeeze them into nooks and crannies that might overwise be wasted.

New technology is helping the caravan leisure battery market, and we are starting to see some new names being offered. One is the Enhanced Flooded Battery (EFB), which was originally designed to be fitted to cars fitted with stop-start systems. Engineered to be able to withstand severe use - and a certain amount of abuse - they are ideally suited for use in caravans and motorhomes.

Lead-crystal batteries are staring to make an appearance, as are lithium. Both are expensive and a bit of a specialist application, so are outside the scope of this article.

For what it's worth, I’m just about to install an auxiliary battery set-up in a campervan and I will be using AGM batteries.

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It's all a bit complicated, isn’t it?

The National Caravan Council (NCC) has introduced a Leisure Battery Verification Scheme to try and make things a bit easier.

It classifies leisure batteries in one of three ways. These are:

Category A batteries are for those who frequently use their caravans or motorhomes away from electrical hook-ups, and so rely on their leisure batteries to provide all their power while they are in their caravan or motorhome.

Category B batteries are aimed at those who will generally use campsites with hook-up facilities, but who might need a greater battery capacity to operate high-draw devices such as motor movers.

Category C the lowest category, and is aimed at those who will generally site their caravans where they can plug into a 240V supply  and so only require a low capacity battery to cover basic stuff when they aren’t plugged in to the mains.

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Topping your leisure battery up

A lead acid battery will need to be kept topped up, and you must only use deionised water to do so.

None of the others need any regular maintenance other than to keep the battery terminals clean and the leads tight.

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Keeping your leisure battery charged

There are two ways to keep your leisure batteries charged. The first is via a 240V battery charger. Places like Halfords sell chargers that will charge both car and leisure batteries automatically, tailoring the output to ensure the best longevity. >

You should check your battery charge levels on a regular basis and you really shouldn’t let it drop below 50%, something that can be a problem if your caravan or motorhome isn’t used very often.

If you fail to maintain the charge in a lead acid battery then it will almost certainly lead to sulphation. If this happens then you can almost certainly say goodbye to the battery and will have to fork out for a new one. A trickle charger, which gives the battery a very low but constant charge, can be the answer here but do check with whoever sold you the battery as to which charger they would recommend.

If you have an electrical multimeter (or have one fitted as standard in your caravan – many do) then you can measure the battery voltage, which will tell you whether it is charged, and if so, how much. Anything over 12.7V is fully charged, while 12.5V is about 75% full, and 12.4V is 50% discharged.

A reading of 12.2V is about 25% charged, while 12V and under is discharged and may well indicate that the battery is too flat to be successfully revived.

Oh, and don’t forget to loosen the filler caps on a lead acid battery when you charge it, will you? Charging a lead acid battery produces an explosive gas, and an exploding battery can be lethal, so wearing eye protection – and possibly some cheap, disposable rubber or latex gloves too - when you are anywhere near a battery being charged is a very good idea.

The Camping and Caravanning Club has some good advice on how to charge your lead acid battery.

The other three types of battery – AGM, gel and EFB – all need better (read ‘more expensive’) battery chargers. Your battery dealer can give you advice – and you should take it if you want to keep your expensive new battery operating at peak performance.

The second way of charging the leisure battery is via your car’s electrical system. This is done via a split-charge wiring harness, which diverts power from your car’s alternator from the car battery to the leisure battery. It gives your car’s starting battery priority so you are never stranded, and only starts to charge your leisure battery when the main battery is full.

The split-charge system also ensures that your caravan or motorhome cannot drain the car battery, no matter what. Modern split-charging systems are very efficient but can cost several hundred pounds to buy and have fitted. However, most will enable you to plug in a solar charging panel, which means you can keep the battery topped up automatically, even if the caravan is parked up for months at a time. This could save you a fortune on new batteries as they shouldn’t ever fully discharge, something that can damage them irreparably.

Power packs

A portable power pack can be a useful way of adding an auxiliary battery without the hassle and expense of wiring one in permanently.

The simplest are just a plastic box with a battery inside and connectors on the outside, while more sophisticated ones contain a split-charge charging system and have a number of different plugs and connectors on the outside to enable you to use it to power a number of different appliances.

I used one to keep a 12V coolbox chilled in The Sahara Desert because I’d borrowed the Jeep and so couldn’t wire in a permanent system. It worked very well indeed, being able to have a cold beer and ice cubes for the evening G&T made it worth every penny!

Prices vary, but a cheap one that you can use to start your car in an emergency too will be about £100, while a heavy duty one with all the bells and whistles including its own charging system will be about £400.

If you have any doubts or queries about the battery or electrical system on your caravan or motorhome then please consult an expert or an auto electrician.

Over 50? Saga Caravan Insurance can offer excellent benefits
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The opinions expressed are those of the author and are not held by Saga unless specifically stated. The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.