Stephen Ward
Caravan & Boats

Battery Type

There are two common battery power levels used in caravans: 85A & 110A. They should be designated as leisure batteries, normally sealed. Motor or vehicle batteries are not the same; they charge differently and should not be used.

 

There are three main categories when purchasing batteries

Type A

These are higher-powered batteries designed for more off-grid applications and running longer without being charged and hooked up to site power

 

Type B

These are the common batteries mostly used; they are for normal use and are designed to be regularly hooked up to site power to charge, and the battery capacity for motor mover, etc.

 

Type C

These are for users who require a lower-capacity battery to cover basic 12v operation of habitation equipment, with short periods away from hook-up and recharging. These are for small day campers or small van conversions.

This battery is designed for the average camper and will work perfectly well.

 

 

 Your battery should have a voltage between 12.75v and 13.4v to be fully charged. A fully discharged battery has a voltage of 12 volts (Twelve). So a battery at 12.5 volts is considered to have 50% power. A 12-volt battery will still power the appliances but may cause dim lights or a slow-running water pump. Motor movers will drain an insufficiently charged battery very quickly, and the mover will either not run or stop-start-stop.

 

To check if your battery charger is working, make sure mains power is on and your battery charger is switched on. If you have a voltage reading indicator, it should show 13.4v or be in the green. If you switch your mains off and the battery indicator drops to 12 volts, then switch on the charger again and observe the voltage indicator rise to 13.4 volts. This is a basic indicator of a working charger unit.

 

Most new caravans will supply a 12v feed to all 12v items even if the battery is flat. Be aware that your charger may overheat or fail if you keep using a battery that is flat or not taking a charge. A leisure battery has thicker lead plates that hold the charge; leaving it to lose voltage and go flat will produce sulphate gas and cause the battery to lose power.

 

IF YOUR BATTERY IS VERY HOT OR HAS A STRONG GAS-LIKE SMELL, DISCONNECT FROM THE CARAVAN AND REMOVE IT, STANDING IT WELL AWAY FROM ANYTHING OR ANYONE AND ALLOWING IT TO COOL. DO NOT USE IT. This battery will need to be replaced. 

 

Battery Care

Leisure batteries require trickle charging most of the time. Your built-in mains charger in your caravan or motorhome is designed to trickle charge at the optimal rate, keeping your battery topped up at the correct voltage.

 

If your caravan or motorhome is stored at your home, then keeping it plugged into the mains with the charger on is sensible. However, to save money when you are not using it, a plug-in timer can be set to charge for a few hours a day.  Just before you are going away I would recommend leaving the power and chargers on a full 24hrs.

 

If you are storing your motorhome or caravan, a good solar panel installed will keep your batteries topped up and prevent them from going flat. 

 

If you don't have a solar panel fitted and you're leaving the caravan or motorhome in storage for an extended period, or over the winter, I suggest you remove the leisure battery altogether. Purchase a specific leisure battery charger, store it in your garage, connect it, and maintain it. These leisure chargers trickle-charge and keep your battery at its optimal level without overcharging.

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DO NOT USE AN AUTOMOTIVE CHARGER FOR LEISURE BATTERIES

IT WILL DAMAGE THE LEISURE BATTERY

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Lithium Batteries

​Lithium batteries are the latest technology; follow the link on the Solar Panel and Battery page to learn more.

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CABLING

The correct cabling for battery charging is essential. Not only to provide efficient charging and electrical power, but also to prevent overheating. The Battery Charging cable should have a minimum 12-volt 16mm² 4AWG cable with 60-amp external fuse protection.

Minimum cable size for 12-volt appliances at different lengths

0.5 meters = 6mm²

1.0m = 10mm² 

2.0m = 10mm² 

5.0m = 16mm² 

10.0m = 16mm² 

The correct cable will also minimise voltage drop across the distance you are running the appliance from the battery. LED lights only require 1.5 mm² two-core cabling unless you have lights with built-in USB. 10 mm² cable will provide enough power for cigarette lighter sockets and USB sockets fused on 10-amp supplies. Remember that the direct voltage from the Solar panel MPPT to the batteries must have adequate-sized cabling. On larger vehicles and caravans, the solar panel connections may be located in the centre, and the batteries may be further away. The distance can be over 5 meters, taking into account the drop down to the floor, the run across, and the ascent to the batteries.

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NOTE

If you are using your home power or a leisure charger in the garage, be sure to check the battery periodically. In the caravan or motorhome, turn off the mains power and take a reading from the meter level or readout. This will ensure that the battery is charging and not failing.

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Battery 12-volt Voltage Calculations

Watts  ÷  Battery Voltage = Current (Amps)

So, example: 200 watts is 16amps

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Inverted Power

Current ÷ Inverter Efficiency = Actual Current (Amps)

An inverter from mains 230V to 12V is about 85% efficient

16amps ÷ 0.85 = 18.8 amps

Inverter specifications may list both continuous and surge wattage. Use Continuous Mode for the calculations, and be aware of the surge capacity when starting larger appliances. Running mains-powered appliances, such as heaters, fridges, TVs, air fryers, and kettles, can quickly drain batteries.

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New technologies are emerging, and battery efficiency is improving. However, using inverted power comes with its own set of problems. These include the number of batteries required to run the equipment efficiently, the wattage needed from the solar panels to recharge the batteries, and the operating losses incurred during use. Adding more battery capacity does not mean you can run all the appliances.

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