Understanding Caravan Batteries: The Different Types + FAQ

Powering the appliances in your caravan requires the use of a caravan battery which unlike a car battery, isn’t meant to provide bursts of energy for the engine. Caravan batteries continuously send a low level of energy over a long period of time. This is because they are not constructed in the same way as car batteries which have different separators and thinner plates.

Types

AGM

The absorbent glass mat (AGM) battery got its name from the glass-fibre mats it has which are infused with acid electrolyte and squeezed between the lead plates. AGM caravan batteries can handle vibrations well, reduce internal resistance and deliver more power whilst having a shorter charging time. An AGM 12 volt battery can be mounted sideways as they have a sealed construction which prevents spills.

Although they have a shorter lifespan, they can go through a lot more charging cycles and can be used as both a car (starter) battery and as a caravan (leisure) battery. You can also discharge them below 50% without causing any damage to the cells.

Open Lead Acid

These were the first leisure batteries and they are still used today. Their inside consists of lead plates sitting in a liquid solution called sulphuric acid. These batteries need to be topped up to maintain their performance and they are also very heavy. Open lead acid batteries can suffer from irreversible damage if discharged below 50%.

Sealed Lead Acid

These 12v batteries cannot be topped, meaning that you can’t remove the caps and pour deionised water. This is actually a good thing and the reason why people call them maintenance-free and also why they are safer than old school lead acid batteries. Sealed lead acid caravan batteries are known as VRLA batteries which refers to valve regulated lead-acid since they let gasses escape when charging – this helps with internal pressure.

Gel

Instead of a liquid battery acid, a gel 12v battery makes use of a thick pasty gel which makes it lean proof and don’t need any maintenance whilst it also has VLRA to control internal pressure. Since these 12 volt batteries can be discharged below 80% without experiencing any damage, they are considered to be better than AGM. But you have to keep in mind that they are not ideal for high load motor movers and have poor performance on high discharge/charge rates whilst being more expensive.

Lead Crystal

Lead crystal batteries can be completely discharged and fully charged with no damage caused whatsoever. This battery technology is new although it’s using similar mat construction and electrolyte as AGM batteries. The lifespan of lead crystal batteries is triple than that of an AGM and they don’t suffer from sulphation damage. Of course, their price is double than that of a standard lead acid battery.

Can You Use a Car Battery in a Caravan?

Although technically you can use a wet cell lead acid car battery to power your caravan appliances but in practise this is not possible. Because, as I mentioned above, a lead acid car battery is not capable of delivering low charge levels for a prolonged time. Again, this is only possible with an AGM battery.

What Size Battery Do I Need for My Caravan?

To make sure you are capable of running basic appliances, most battery setups in caravans will consist of two 12amp batteries which are going to be re-chargeable through mains 240V power.

Calculating the Size of Your Battery

In order to select the right battery you’ll need to calculate the amps of each device and appliance in your caravan and see if the amps in your battery are going to be sufficient. The way to go about this is to divide the wattage and voltage of each device/ appliance. For example if your tablet uses 5W of energy on a 12V power source it will use 0.4 amps, so a 100Ah battery will be able to deliver power to it for 250 hours. Then just multiply the amps of every device/ appliance by the approximate number of hours or minutes you’ll use it a day. For example the 0.4 amp draw mentioned above when multiplied by a 3 hour use it will end up using 1.2 amps a day.

But you cannot actually use every amp of the battery unless you get a Lead Crystal caravan battery. For the rest of you who just want to spend a reasonable amount using a 12v battery, you’ll need to calculate the amp draw of every piece of technology that uses electricity. Separate the 12 volt and 240 volt devices and when you get the amp draw of one, multiply it by how many of these devices you have in the caravan and then multiply the outcome of that with the total number of hours a day. Stack that up to the amps of your batteries, the number of batteries, the allowed discharge percentage (depending on the type of battery) and the usable Ah.