What’s The Difference Between A Leisure Battery And A Car Battery?

Leisure Battery vs. Car Battery Comparison

Let’s look at the differences between the two battery types in more detail.

Type of power output (discharge)

Leisure batteries are built specifically for a slower, steadier discharge.

That means the power output of the battery is relatively small but it’s over a longer time.

Think about what you use a leisure battery for. It’s normally to power electrical devices like fridges, TVs and lights. Those things require a constant stream of relatively low power.

A leisure battery is constructed to provide for that type of power.

A car battery on the other hand, is built to provide an extremely large burst of power for a short period of time.

In this case, think about the primary job of a car battery. It’s job is to start the engine.

A car’s engine needs a huge amount of energy given to the spark plug to start the engine, but only for a very short time.

So a car battery is built to be able to deliver a high Amperage boost that provides enough energy to crank the starter motor.

Ability to cope with deep discharge

A leisure battery’s internal components are designed for coping with the battery being deeply discharged. A high quality one (like those in the Superbatt Silver 9000 range of leisure batteries), in particular, can cope very well.

We’ll get into more detail on that in the Inner construction section but basically the inner design means that a leisure battery can be discharged to 40, 50, 60% Depth of Discharge (DoD) and it will be fine. This won’t harm the battery (though to maximise battery lifespan, it’s better not to go above 50% DoD too often).

The best Lithium leisure batteries, however, can be discharged to 90-100% with no issues.

A car battery will be damaged much more easily if you discharge it to 50% DoD and beyond.

This higher level of discharge is likely to result, over time, in desulfation of a car battery. That’s when lead sulfate develops on the lead battery plates, and effectively choke the battery’s ability to store charge and give power to your appliances.

This is the main reason why long-term use of a car battery as a leisure battery will result in a very short lifespan.

Sulfation doesn’t develop instantly, the first time you discharge the battery to a high level. Rather, it’s a process that happens over time.

If you continue to use a car battery over several weeks and months, more and more lead sulfate crystals will gather and harden on the battery terminals. Soon enough, the battery will be dead.

When considering the points of difference between a leisure battery and a car battery, the ability to handle high discharge is a very significant one.

Ideal charge cycle

A leisure battery is designed typically for a discharge level of 50% DoD. Many caravan, motorhome and campervan users will go above this level quite regularly.

Lead-acid leisure battery manufacturers, though, design the battery with this 50% DoD in mind and often give the expected lifespan of the battery as x number of cycles at that level of discharge. For example, they may say you’ll get 3000 life cycles at 50% Depth of Discharge.

Leisure batteries, then are built with this type of usage in mind, they’re ideally structured for that level of discharge.

As with any lead-acid battery, it should then be charged back to 100%. That way, the battery will last longer, and it staves away sulfation (which happens as a natural chemical process to all lead-acid batteries).

Gel batteries have their own particular charging needs. Here’s all there is to know about gel battery charging.

Car batteries, however, are designed with the primary purpose of starting the engine.

Car battery manufacturers do not design their 12V batteries to deal with a high level of discharge.

They design them for a large, short discharge of power. Following that, the charge should be immediately topped up with power from the car’s alternator. That’s what happens when you drive – the alternator sends charge to the battery.

For best health practices, a car should be driven long enough that the battery charge is returned to 100% charge. If not, and the person uses the car only for short journeys, then a car battery charger should be used to get the charge back up to 100%, ready for the next time a big boost is needed to start the vehicle.

A car battery also provides slow, steady power for electronics, but these tend to be very small current draws, and will only majorly affect the battery if it’s not getting enough charge from the alternator.

Inner construction

This is the core of the difference between a leisure battery and a car battery.

All lead-acid batteries have lead plates inside them, which make contact with an electrolyte solution. This electrolyte is a mixture of sulphuric acid and distilled water. For most typical lead-acid batteries, known as Flooded or Wet, the electrolyte is in liquid form and flows around the lead plates.

In the case of AGM batteries, the electrolyte is absorbed on fibre glass mat separators. This has several advantages, such as preventing acid stratification (when the sulphuric acid and distilled water become poorly mixing, meaning less chemical reactions and therefore less power in the battery). Gel batteries, meanwhile, have the electrolyte is mixed with silica (sand) and this forms a gel-like substance.

Leisure batteries have thicker plates, and fewer of them.

Why? Because thicker plates release their energy more slowly. That suits leisure applications better, since appliances need a relatively low amount of power over a longer time.

The lead plates have relatively small surface area, compare to car batteries, so the electrolyte has less contact with the plates. That means less chemical reactions can take place. That’s perfectly fine for leisure batteries, since there’s no need for a sudden, major burst of power all at once.

Leisure batteries are built for better cyclic durability. That means it copes better with higher discharge levels as we said earlier. The reason is the nature of the lead plates. The thicker plates, and fewer of them, means that less sulfation will occur. There’s less contact between the lead plates and the electrolyte, and so less sulfate crystals will develop when the battery is in a discharged state. As a result, leisure batteries are not damaged by relatively deep discharge levels.

Car batteries have a higher number of lead plates, and they’re thinner.

Why? Because it allows for more contact between the electrolyte and the lead plates. As a result, more of the chemical reactions between the lead and the electrolyte take place, and it’s these chemical reactions that produce the electrical power. Therefore, much larger amounts of power can be produced.

That’s very suited to car batteries, which need a significant boost of power to start the engine.

The higher surface area allowing more contact between the plates and the electrolyte also means car batteries have relatively poor cyclic durability. They don’t cope well with higher levels of discharge.

That’s because the higher surface area means that more lead sulfate crystals can develop on the battery plates, when the battery is discharged to high levels, and when it’s left in a discharged state. The longer it’s in a discharged state, the harder the sulfate crystals become and the more attached they get. This blocks the battery from storing and delivering power.

As a result, a car battery will quickly die if it’s used as a leisure battery, with deep discharge and longer discharge cycles.

Lifespan

If you’re using each battery in its correct mode of usage, lifespan is not hugely different between car batteries and leisure batteries.

3-5 years is most common for a car battery, depending on your climate. In the UK, it tends to more towards 5 years.

If you treat your battery how it wants to be treated, it can be longer. That means longer journeys, or using a car battery charger, to make sure it’s getting a 100% charge as often as possible. And as little time as possible in a discharged state. A desulfator charger or desulfator can extend its lifespan by several years, since they remove sulfation.

If you use a car battery as a leisure battery, it will die fast, for the reasons we’ve mentioned. 6 months? A year if you’re lucky?

Leisure batteries can last a similar amount of time, and maybe a little longer.

With them, it depends on your charge cycles. Are you consistently discharging it to 50% and then recharging fully?

If so, you can get 7-8 years or even more. In the case of AGM batteries (here are the top AGM leisure batteries in the UK) this is quite realistic, and in the case of Lithium batteries, you can get 10 years easily, and 15 years is not out of the question. Here’s how long a leisure battery lasts.

You may consider using a leisure battery tester to keep an eye on charge and health levels.

If you have a lead-acid leisure battery, using a desulfator-charger or desulfator can be a great way to extend its lifespan, even by several years, just like it does for car batteries.

A DC-DC charger can also ensure you much more effectively charge leisure batteries while you drive (which makes them last longer!). The CTEK D250SE is the best DC to DC charger.

Typical Size

This is a major point of distinction for a leisure battery vs car battery.

With leisure batteries, there’s quite a wide range of sizes that people use.

If you just use your motorhome or caravan for the odd couple of days away, even an 80-90Ah leisure battery can be enough for you.

While those who want to really go for off-grid living might have a battery bank of 3 100Ah batteries, making 300Ah in total.

The advent of Lithium batteries, and their now-affordable cost, has allowed many people to reduce the size of their battery bank. For example, they may have needed 3 100Ah lead-acid batteries, but now a 200Ah Lithium battery provides all the power they need, and with a massive weight saving.

Car batteries are different, they don’t vary so much in size. A typical car battery is around 50Ah, but they can be as small as 40Ah for a small car and 70-80Ah for a larger vehicle.

Car batteries are much smaller because their only major power expense is that initial burst of power. It doesn’t require a large capacity battery to produce that power because it’s for a very short time. Then the battery should be charged constantly while you drive, via the vehicle alternator. So the power is quickly topped up back to 100%.

Leisure batteries need to be much bigger, for most people, since they are for providing sustained power over a longer time, and will only be occasionally recharged.