Know your battery types
When it comes to batteries, there's a lot of choice out there. But how do you know what's best for your needs? Allow us to help you choose...
Flooded lead acid batteries
The most common leisure battery is a lead acid unit, where lead plates are submerged in sulphuric acid (hence the term ‘flooded’). The acid acts as the electrolyte. Many of these batteries need topping up with ionised water, at least on an annual basis, but sealed batteries will offer a
low-maintenance alternative as they have an excess of electrolyte solution to compensate for any water loss.
In a gel battery a silica gel is added to the battery acid, which solidifies the electrolyte and prevents it from spilling. This makes a gel battery useful for applications such as jet skis where the battery may be upended (less of a risk in a caravan, but a nice-to-have feature all the same). Gel batteries generally cost more and offer a lower capacity than lead acid batteries.
On the plus side, however, they are typically sealed and therefore require no maintenance. Just beware that it is important not to exceed the maximum charge voltage when recharging.
Absorbed glass mat (AGM) batteries take their name from the glass-fibre mats which are impregnated with acid electrolyte and squeezed between lead plates in this type of battery. This reduces internal resistance and delivers more power and shorter recharging times. AGM units offer the same no-spill, anti-vibration advantages of gel batteries, but hold their charge better.
AGM batteries are more expensive than flooded batteries, but ought to deliver substantially more recharging cycles and therefore last longer.
The electrolyte in a lead crystal battery is, unsurprisingly, crystalised acid, which sits between the lead plates and cannot leak. This is still quite new and expensive technology, but their design makes them particularly forgiving of heavy discharge (down to zero volts) without any impact on their life cycle, and they can be recharged twice as fast as a regular battery.
Manufacturers claim they will last at least twice as long as standard lead acid batteries, so their total cost of ownership may be competitive.
The power technology behind mobile phones is now starting to appear in caravan leisure batteries. Lithium ion’s great advantage is its size and weight – with no lead, they are less than half the weight of a standard lead acid battery, and their high energy density means they occupy much less space.
These two factors make them highly attractive to caravanning, as does their ability to withstand discharges of more than 80% of their capacity (compared to 50% for lead acid batteries) before needing a recharge). Moreover, there’s a minimal decline in voltage as the battery discharges, and they can be recharged rapidly.
The downside is cost – lithium ion batteries can be up to 10 times as expensive as lead acid – close to £1000 for a 100Ah unit.