Lead v Lithium Leisure Batteries: A caravanner's guide
Lithium leisure batteries, although more expensive, are around half the weight of lead acid batteries and hold their voltage better
Words by Terry Owen
Lithium battery technology has come on in leaps and bounds over the last few years. They are still expensive compared to lead acid batteries – but they’re coming down in price all the time, making them a tempting consideration for those who spend a lot of time caravanning off grid.
How much are lithium leisure batteries?
Well, a Relion 100Ah lithium battery, for example, would cost around £925 – but only weighs 13 kg. Alternatively, a budget Xplorer lead acid battery with a 110 ampere hours (Ah) rating and weighing 23 kg costs around £95.
A more expensive lithium leisure battery, from RoadPro, would cost £140 and weigh 24 kg. Lithium batteries have several advantages over lead acid types but, aside from price, there are some downsides, too. You can dismiss the safety concerns about lithium batteries from a few years ago, as the technology has advanced and today’s batteries are safe. The technology we are talking about here is lithium iron phosphate (LiFePO4). All the leisure batteries of which I’m aware use this advanced technology.
Let’s start with the positive points for lithium leisure batteries
- For a given physical size, a lithium battery is less than half the weight of a lead acid one. Although it may have a similar capacity, say 100Ah, much more of that is usable, without damaging the battery. If a lead acid battery is discharged much below 50% of its capacity on a regular basis, it will suffer permanent damage. A lithium battery can be discharged right down to 20% without damage. The result is that you can get more power out of the battery before you need to recharge it. Furthermore, a lithium battery will hold its voltage much better as it discharges, whereas a lead acid one will start to tail off much sooner, particularly in cold weather.
- Lithium batteries can also be charged and discharged much more rapidly than lead acid types, without damage. A clear win for lithium, then? Not quite, especially if you’re looking for a ‘plug and play’ replacement for lead acid. To achieve a full charge, a lithium leisure battery needs a charging voltage of 14.6V. But the charging units fitted to caravans are set to 13.8V, although some will increase this to 14.4V under load. These levels are chosen for lead acid batteries and give a reasonable combination of charging without gassing.
- However, they will not charge a lithium battery to optimum performance. This means you'll have to charge the battery with a suitable charger before use. Alternatively, to charge a lithium battery in a caravan you would need a dedicated lithium battery charger. You would also need to protect against charging in freezing conditions. Correct charging is paramount for good battery life. This includes balancing the cells – the individual compartments within the battery, each of which produces about 3V – to an equal state of charge.
Lithium leisure battery challenges
- Lead acid batteries automatically balance the cells, but lithium batteries do not, and cells that are subjected to too much voltage can fail. This can be a problem when using solar panels with charge controllers. It’s important that lithium batteries for leisure use come with an in-built battery management system (BMS), as cell balancing is one function it should perform. Also, lithium batteries should not be charged in temperatures below 0°C, as this may result in permanent damage. It's the role of the integral BMS to prevent damage through issues such as those raised above.
- The electronics needed are complex and inevitably add to the cost, especially for the more comprehensive types. For example, cold weather charging can be facilitated by employing internal heaters to automatically warm the battery first. Of course, while this may be fine in some situations, it’s clearly less than ideal when caravanning off grid. The bottom line here is that, under load, a fully charged lithium battery will outperform a similar- capacity lead acid one any day; the challenge is in ensuring the full charge in the first place.