If you are looking for a way to provide power to your off-grid campsite, a 12v battery box could be what you are looking for.
A battery box is a container (usually plastic), with a lid, that you place a heavy-duty deep cycle battery inside, that keeps the battery safe for transportation and provides ports to both draw current from the battery (cigarette plug/USB, etc), and ports to feed charge into the battery.
Choosing A Battery Box
There are many different battery boxes on the market, and trying to find the best battery box for your situation can be a bit overwhelming.
There is no ‘perfect’ battery box, they all come with their own strengths and weaknesses and the best one for you will depend on the needs of your specific situation.
Battery boxes are an alternative to similar ‘all-in-one’ portable power packs, where the battery is sealed inside the unit.
The benefit of battery boxes over all-in-one units is that with a battery box you can change your battery if you want or need to, as opposed to having to discard the whole unit if the battery stops working or becomes problematic.
But as you look around there are certain themes that keep coming up, and things you should think through, as you decide on the best battery box for you.
This article looks at some of those themes and gives some suggestions of the things you should think through before making your decision.
There will be no mention of any specific products, just the overall characteristics, and qualities that different boxes may have.
Battery Box Price
Battery boxes come in all shapes and sizes and as a result, they are available at many different price points.
Cheaper ones can be found for around $70, and the more expensive ones can cost in excess of $500.
If price is not an issue for you then you just need to figure out your other requirements and find the best match for those, but if the price is important, start thinking now about your upper budget limit, and prioritizing the features and characteristics that are most important to you.
I don’t see this topic discussed explicitly in many forums or descriptions for products but to me, I think it’s really important to think about. Most battery boxes are rectangular in shape and have carry handles on each side of the box for carrying.
Due to the way some of these boxes are designed, this is the only way they can provide a safe enough way to hold the weight of the box and battery.
But some units are engineered in a way that they can offer a folding carry handle on top of the unit, to pick with one hand.
I’m not sure which method of carrying/lifting is best for your body overall, but all I can say is that my box has a side handle, and with a heavy battery in there it can be difficult to get around, and I find myself wishing it had a top handle.
This handle issue should not be your main consideration though.
The best battery box for you may have the side handles, and if so you should probably go with it, just be aware of this difference, and perhaps try a few of the different styles out to get a feel for the grips and see what you think you will be able to manage.
The nature and number of devices you hope to connect to your battery box are going to be a determining factor in the best box for you. Think about your minimum viable setup, and what you must have power for, no matter what, and work from there.
For us, our main power needs are 12v connections for our LED lights and USB ports for charging for phones and tablets, etc. But many others find a fridge to be the number one appliance, and lights and USB issues secondary.
It doesn’t matter what your preference is, just that you are clear on what type of ports you need, and how many of them you need.
Different types of 12v ports you come across on different boxes include cigarette plug, hella socket, and merit plug. Some units also include Anderson plug connections, and also USB connections.
Keep in mind that there are many ‘double adapters’ and converters available for 12v cigarette ports.
So if you have a single 12v cigarette port, but you really need two, it won’t cost you much to buy an adapter to give you additional outputs, as long as the overall power draw won’t exceed the port’s fuse.
Some of the high-end expensive battery boxes are equipped with pure sine wave inverters giving you the ability to plug in 240v appliances to your battery.
These inverters are usually capable of proving up to 300 watts of power which is enough to power a small 240v device, but won’t be suitable for high draw appliances like microwaves and power tools.
For most people an inverter is ‘nice to have not a ‘need to have’, but there may be a reason in your case that inverter is more critical, so make sure you think this through.
Type of Battery
There are many different types of battery technology available for you to choose from when picking a deep cycle battery from lead-acid batteries (wet cell, AGM, Gel Cell) to the more advanced (and expensive) lithium batteries.
If you don’t have any strong thoughts on this, then a default recommendation would be to consider AGM batteries.
They provide a lot of advantages over traditional wet cell batteries, in terms of power deliverability and safety, and are still reasonably affordable. AGM batteries should work fine in all battery boxes currently available.
However, if you are looking at more advanced technology (like lithium batteries), just double check that the box you are considering is able to charge that type of battery as some batteries are sensitive to the way they receive electrical current and need specialized circuitry.
When we talk about battery size we are referring to both the dimensions of the battery and also the battery capacity itself. These two characteristics are highly correlated in that greater battery capacity leads to a larger battery size.
When we talk about battery capacity we are talking about how much charge is inside the battery that you can draw to power your appliances.
Most battery boxes are designed to fit and work with a battery up to 100Ah, even 120Ah, in size.
Most deep cycle batteries you buy (apart from Lithium-based batteries) will provide you with 50% usable capacity meaning that for a 100Ah battery you will have 50Ah of usable power.
Battery Box Display
Keeping track of the level of charge in your battery is important to make sure you know when your battery is getting flat and can charge it, and also to make sure you can monitor and adjust your consumption if you find it is going down a lot quicker than you expected.
Most battery boxes include a voltmeter, which gives you a constant reading of the level of charge in your battery and this information will guide you on when to re-charge and when to slow your consumption.
But some of the cheapest units don’t have this, Some only have LED’s that light up to give you high-level information like ‘fully charged’, ‘flat’, ‘nearly flat’, ‘charging’ etc.
This LED setup is not a deal-breaker, but for a few more dollars you could get a box with the voltmeter indicator which is good information to have if you can get it.
More expensive boxes also include other types of battery level indicators and give you time estimates of how many hours and minutes your battery has to remain, taking into account current usage and the type of battery you have.
These again are ‘nice to have’, but as a minimum, I would recommend trying to have a voltmeter display included on your box.
All battery boxes are equipped with fuses and isolator switches that shut the unit down if too power flow exceeds certain levels.
The only thing to check here is that the ports you want to use allow sufficient flow for the device you want to plugin.
Nine times out of ten, it won’t be an issue, but it could be that your fridge draws more current than the 12v port it is plugged in to is designed to give, and you could keep tripping the isolator switch and cutting off power to your fridge.
So it is worth double-checking as this would be very frustrating.
Most battery boxes will be equipped with positive and negative power terminals that you can connect to multiple different battery chargers.
In my case, I just connect my 12v automotive battery charger to the ports, and that works fine, but you can also purchase dedicated additional chargers for this purpose that have variable voltage options and can adjust how much power they are feeding the battery based on its level of charge.
You can also hook up solar panels to these ports if you have alligator clip connections on your solar panel regulator.
Other boxes also provide an Anderson plug connection so you can plug your solar panel directly into the unit.
I personally prefer this method of solar panel connection, just because the clip connection is so sturdy, whereas the alligator clips are a bit more vulnerable to being knocked off by young kids or stray limbs.
Though it shouldn’t be your primary consideration, there are many different shapes and sizes, and colors you can choose from, so pay a little bit of attention to the box style and shape and whether is a good fit with the rest of your gear.
But don’t let this sway you too heavily, the core functionality and battery dimensions should be the key drivers in your decision making.
In summary, the amount of money you have to spend, the outputs you need, and the size of battery you are hoping for should be the main drivers of your decision when looking to purchase a battery box.
If you just want something to power your fridge when you are away, then a cheap unit could do this perfectly, but if there are multiple people with phones to charge, and fridges and lights, and more, then you might need to look at a mid-range box for $100-$200.
If you want an inverter then you need to be prepared to pay closer to $500, and at that price, you will get a lot more display options to help with monitoring battery usage and time remaining.