Charging Your Leisure Battery
If you own a caravan or motorhome, then it’s important to get to grips with your leisure battery. Understanding how to maintain your leisure battery will ensure a longer service life of your battery, which in turn will help reduce the costs of running your caravan or motorhome.
The service life of a leisure battery will very much depend on how frequently it’s discharged, how deeply it’s been discharged and how soon after, being discharged, has it been recharged. A leisure battery kept in a good state of charge will last much longer than one left for prolonged periods of time in a low state of charge. You really want to avoid having your battery in a low state of charge for weeks or months.
A leisure battery is used as a source of power to run varies appliances you may have, either in your caravan, motorhome or perhaps whilst your camping. Leisure battery’s being used in caravans and motorhomes etc are generally 12 volt, and should not be confused with a vehicles starting battery, which are designed to supply a surge of current in order to turn the vehicles engine over so it can start. In contrast, a leisure battery provides a moderate current constantly in order to power electrical equipment you would use whilst in your caravan, motorhome.
Traditional leisure battery’s were of a wet, flooded lead-acid type but as technology has moved on we now see, AGM, Gel and Lithium LiFePO4 battery’s.
The chargers generally fitted in caravans and motorhomes are not really battery chargers but a way of providing a power to supply the 12 volt equipment onboard. For this reason they are not ideal for fully charging a leisure battery, although more modern ‘intelligent chargers’ are better in this respect.
Removing your leisure battery periodically and charging it with a good quality leisure battery charger will help to keep your leisure battery in excellent condition. The important factor with any rechargeable battery is to know when the battery needs recharging and for how long.
It is also important to know that leisure batteries that use lead-acid technology like wet lead-acid, AGM and Gel batteries over time lose charge, even when no load is applied. Some types of lead-acid technology like AGM are more resistant to this type of discharge but nevertheless it occurs, and as a rule of thumb, batteries in storage and not in service should be charged every three months or so.
Battery Removal
It is recommended to remove the battery from the caravan or motorhome when you want to charge the battery, but if this is difficult then it is important to disconnect it completely so as to remove the possibility of something interfering with the charging process.
- Always make sure you are wearing safety protection glasses for your eyes and gloves for your hands. Latex gloves can provide the dexterity that you need whilst protecting your hands.
- Firstly, you will need to locate the battery, please check the user manual that came with the caravan or motorhome to locate it.
- Once you have located the battery, make sure you have the correct tools to remove the battery.
- Locate the battery’s black negative terminal, using a spanner or socket (usually either 13mm or 10mm) loosen the nut and once the terminal is loose free the negative terminal from the battery. IMPORTANT – always remove the black negative battery cable first.
- Locate the battery’s red positive terminal, using the spanner or socket, loosen the nut and once the terminal is loose free the positive terminal from the battery.
- Lastly, remove any hold-down bracket or strap securing the leisure battery in place by undoing the bolts, the battery can then be removed safely.
Battery Charging
- Once the battery has been removed then make sure the battery and the battery terminals are clean and dry.
- Make sure your battery charger is the correct power for your battery, in most cases your charger should be approximately 10% capacity of your battery. Example: if your battery was a 100Ah battery, then your charger would ideally be a 10 amp charger. Leisure batteries can range between 60 and 200 Ah, this mean you can happily use a 6 to 20 Amp battery charger.
- Connect your intelligent battery charger to your battery by connecting the positive (Red) lead first to the positive terminal on your battery.
- Connect the negative (Black) lead to the negative terminal on your battery.
- Then you can plug your intelligent battery charger into the mains power and turn on the battery charger. If you have various modes on your intelligent battery charger then select the correct mode for your battery. If you are unsure, please refer to your owners manual.
- With intelligent battery chargers, once they have charged the battery fully they will switch to a float charge, meaning this just keeps a pulse charge going into the battery until you’re ready to take it off charge and use it. With this type of charger you can leave you battery charger on for 12 to 24 hours or so and then your battery should be fully charged.
How long you charge a leisure battery for will depend on its level of discharge and the type of technology of the battery. If a leisure battery has been subject to extremely deep discharge, you may find that it’s ability to recover has been significantly impaired, if this occurs it will never regain its former performance.
Sulphation
As your lead-acid battery’s voltage drops to around 12.4 volts you see the acid stratification process start to take effect, and as the process increases lead sulphur builds up on the plates. In order to reverse this process you need to charge the battery, the chemical reaction in the charging process reverses the effects of the acid stratification, and the battery should return to a fully charged state.
However it is IMPORTANT to point out that if the stratification process has been left to build up over a longer period of time (i.e.many weeks or months) without the battery being recharged then the lead sulphur will begin to crystallise, this is bad news as it is extremely difficult to reverse and almost always leads to permanent damage and reduction in the capacity of the battery. This effect is know as sulphation and some battery chargers have modes that can avoid this and in some cases maybe able to recover minimal sulphation damage.
Disconnecting Your Battery Charger
- When your battery is fully charged and you want to disconnect the battery charger, make sure you turn the power to the charger off at the wall (the mains power outlet).
- Remove the negative (Black) battery lead first.
- Remove the positive (Red) battery lead.
- At this point it would be a good idea to test the battery with a battery tester, if you have one, or take it to a professional who’ll test it for you.
- Once you’ve had your battery tested and it has passed, you’ll be ready to install the battery back into your caravan or motorhome.
Useful Tips For Leisure Battery Charging
- Check the state of charge of your leisure battery at least once a month.
- Once you have used the leisure battery, recharge it as soon as possible. This not only maintains good battery health, it also means that the battery will be in a ready state when you need to use it the next time.
- Once in every six weeks or so, remove the battery and charge it with the manufacturer-provided (or recommended) leisure battery charger.
- If using a non-sealed battery which requires electrolyte top-up, always use distilled or de-ionised water for topping up, never use tap water as it may contain minerals to contaminate the electrolyte.
Checking The Charge Level
Most modern caravans or motorhomes have a built-in battery monitor, however some of the older models may not. We recommend checking your battery charge levels with a voltmeter or multi-meter, below we have a quick reference chart to assist your checks.
Prior to taking the readings, ensure all electrical appliances and systems are switched off.
Meter Reading Approximate Charge Level
12.7V or above 100%
12.5V 75%
12.4V 50%
12.2V 25%
12V or less Discharged
Glossary
AGM – (Absorbed Glass Mat) A type of battery technology where the electrolyte is soaked into glass fibre mats and tightly packed between the lead plates.
Ah – Ampere hours. A unit of measurement based on current in amps (A), multiplied by time in hours (h). This measurement can be used to compare the capacity of different batteries.
Boiling dry – A result of the water content of the batteries electrolyte is lost through gassing, such that the plates of the battery become exposed to the air. This will usually occur when a battery has been over charged.
Cycle life – The total number of charge and discharge cycles a battery can maintain during its service life.
Deep cycle – A battery which is designed to be discharged to 50% of its capacity before being recharged.
Electrolyte – A liquid or gel substance inside a battery which allows electricity to flow between the positive and negative terminals by carrying ions (charged particles).
Float charge or charging – A type of charging where the battery has already been fully charged and switches to a float mode, a constant voltage supply pulsing to maintain a battery in a fully charged state.
Gassing – This occurs during the charging phase of a battery when it nears fully charged and any extra current starts electrolysis of the water in the electrolyte.
Gel battery – A type of battery technology used in VRLA batteries where the electrolyte consists of a gel, which is resistant to spillage and has its own set of strengths and quirks.
Self discharge – A process where by a battery slowly discharges even without a load applied to it.
Trickle charge – A type of charge which is a very slow and steady method of charging a battery, typically at the same rate the battery self-discharges, so it stays fully charged without overcharging.
VRLA – Stands for (Valve Regulated Lead Acid) battery. These batteries are low maintenance where any charging gasses should recombine into water and can be safely vented if they do not.
