The best battery for your battery box will depend on a number of factors, including your budget and your power needs.
Batteries come in all shapes and sizes, and types and are powered in multiple different ways. The first big decision is to decide what type of battery you think is best for you, and then worry about the size and the brand after that.
Choosing the best battery for your battery box: Types of Battery
Lithium Deep Cycle Battery
Heavy-duty deep cycle batteries are available in a variety of lead-acid and lithium configurations.
Lithium deep cycle batteries are more recent technology and come with many benefits, but also a higher price tag. Lithium batteries are lighter than lead-acid batteries and can be regularly discharged to a lower level than lead-acid batteries.
This is because deep cycle batteries have a limit to the amount of charge you can use before you need to recharge them, and if you go below that level you can cause damage to the battery and decrease its longevity.
Most lead-acid batteries are designed to manage a 50% depth of discharge (DoD) before you need to charge them again, however lithium batteries can handle an 80% depth of discharge on a regular basis without causing any damage to the battery.
So though they are more expensive than their lead-acid counterparts, they are much lighter (and thus easier to carry around), and you get more usable battery power, from an equivalently sized battery.
For a 100Ah lead-acid battery, you are going to get around 50Ah of usable charge before you need to recharge them.
However with a lithium 100Ah battery, you could get up to 80Ah’s of usable power before you need to recharge, and it can do this repeatedly without damage to the battery.
Lead Acid Batteries
There are a variety of different lead-acid batteries available for consideration including wet cell, absorbent glass matting (AGM), and Gel Cell.
Wet cell lead-acid batteries are the cheapest, and they have been around the longest but they come with some downsides when being used as deep cycle camping batteries.
Wet Cell batteries are filled with liquid which, for one, is dangerous if spilled, and two, needs occasional maintenance.
This potential spillage of this liquid means these batteries cannot be in the same spaces as humans and need to be somewhere separate and safe (i.e. engine bay, ute tray).
Further, the way these batteries behave is that they give off a large amount of power, to begin with, but then their ability to deliver power slowly wanes, making them less suitable for camping scenarios where you want a battery to deliver a steady slow charge over a long period of time.
Absorbent Glass Matt (AGM)
AGM batteries are a newer technology and utilize a matt material to contain the lead acid, as opposed to having a liquid that flows around inside the battery.
AGM batteries don’t need any maintenance as they are sealed units, so there is no safety concern like with wet cell batteries.
A further benefit of AGM batteries is that they can deliver a steady stream of power over a long period of time, and don’t suffer from the same performance issues as wet cell batteries.
They cope well in most temperatures and are not prone to damage from overcharging.
The other type of lead-acid battery is what is called ‘gel cell’ which converts the lead-acid into a gell-type substance.
Though this provides superior performance and resolves the same safety issues associated with wet cell batteries the gel is very sensitive to overheating so need a very specific charger.
And they also struggle to perform in colder temperatures, in comparison to AGM and wet cell batteries.
Overall, in terms of the type of battery, I personally went with an AGM battery, and have heard many other battery suppliers provide the same advice. Yes, Lithium has some advantages, but it comes at a significant cost.
An AGM battery resolves most of the main issues with wet cell batteries in that they are safer, and deliver a more consistent stream of current, and are still very affordable.
The right size battery for your battery box will depend on the space available inside the box. The majority of battery boxes are designed to fit a battery of between 100Ah – 120Ah in size.
A 100Ah to 120Ah size battery would suit most people well, and provide a consistent stream of power over a few days, and maybe longer depending on how many things you have plugged into it.
There are dozens of different brands to choose from, and for a comparable battery (e.h. 100Ah AGM battery), you will notice a significant price discrepancy.
This is often due to the quality and size of internal components used to build that battery.
For example, the Thumper Redback batteries use high-quality heavy-duty parts inside which means you can charge it much quicker, and get a high-quality flow of power, but you pay for this quality.
If you are an occasional camper heading away for a weekend every now and then, a cheap one will probably do you fine.
But if you go away regularly and have your battery as part of your core setup, then it may be worth spending the extra money on a high-quality battery.
In summary, I think the majority of people would be well served by a 100Ah AGM battery.
If you have the budget, you might want to think about Lithium, but a good quality AGM will give you great performance and be robust and reliable in many conditions.