Batteries do two essential things for your campervan electrical system. The first is that they store energy when you aren’t generating any. The second thing batteries do is smooth out energy delivery.
In some situations you’re getting a constant supply of power. Being connected to shore power or electrical hookups is an example of this. But most times the power you’re collecting is coming in chunky waves. If you didn’t have batteries, your lights would go dim when the sun went behind a cloud or get too bright when you rev your motor and alternator.
What Is A Battery?
Batteries use chemistry to take the power you collect and store it as potential energy, ready to be used later. Batteries come in different voltages (2V, 6V, 12V, 24V) which is essentially a measure of how fast they can push electricity through your campervan system. A 6V battery doesn’t have enough “speed” to make a 12V light turn on. Similarly, a 24V battery connected to a 12V light will likely blow it out.
Batteries have a positive (+) and neutral (-) post. Energy wants to travel from the (+) to the (-) and will do so at every opportunity through conductive materials. When we let the energy through in a controlled way (through wires) it powers our devices as it moves itself.
This can be visualized as a dammed up creek with a small exit water pipe that passes through a water wheel, making it spin. If the dam has too much pressure, it will break the wheel.
Batteries should never be punctured or dropped. You should also never touch both (+) and (-) posts at the same time with a conductive material such as a metal wrench. They should not be in extreme temperatures or charged too quickly or with the wrong voltage.
If you have never worked with vehicle batteries before, it is wise to grab a mentor to look over your shoulder as you get more familiar with them. 12V DC systems are relatively safe compared to 110V AC household wiring, but there are still plenty of things that can go wrong.
There are four common types of batteries for vehicles and they each operate a little bit differently. They are:
- Starter batteries
- Deep-cycle batteries*
- Hybrid batteries (AKA Marine or Golf Cart batteries)
- Jumper batteries
Starter batteries do exactly what it sounds like; they start your motor! Starter batteries (also known as cranking batteries) are designed to push out a large amount of power in a short period of time to turn over all the moving parts of your engine. They are usually rated in CCA (Cold Cranking Amps), which is a measure of how much instant power they can deliver to the starter.
Although starter batteries can be used to power household electronics like refrigerators and televisions they are not designed for this purpose. If you discharge and recharge them on a frequent basis, their lifespan will be shortened significantly. They won’t even last a year before they die.
Starter batteries shouldn’t be used for anything other than starting the car
Deep-cycle batteries are the workhorse of the battery world. These have thicker internal plates that provide power for long periods of time and can be discharged and recharged frequently. The consistency of a deep-cycle battery makes it the ideal solution for long-term use. Deep cycle batteries work well as secondary batteries or as a backup for other power sources such as a generator. Because of their build, they are not able to provide as much instantaneous power as starter batteries.
Deep-cycle batteries are rated in Ah (Amp-hours). Amp-hours are a measure of how much electricity the battery can hold. More Ah means more power storage. For instance, a 50Ah battery will keep a light on for twice as long as a 25Ah battery. You can read more about Amp-hours in our post on calculating energy needs.
Deep cycle batteries are the ideal choice for most van setups
Hybrid batteries (Golf Cart, Marine, Dual-purpose, etc.)
These are the jack of all trades. Their internal makeup can handle quicker discharge but they are more resilient in frequent charge cycle situations.
You can envision why this type of battery was developed: boats need to start the gas motor but also be able to power electronics such as radios, trolling motors, and sound systems when the motor is off. Golf carts require a lot of power at full throttle but need to be able to run for a long period of time.
Hybrid batteries work fine in a campervan. They won’t last as long as a deep-cycle, but are often cheaper and in the case of some electronic requirements might even be the best choice.
Hybrid batteries also work well, particularly if you need quick discharging capabilities
These are batteries designed for emergencies that can deliver enough juice to jump your starter battery if it’s dead. They often come with USB ports so some people are tempted to use them to charge their devices, but they are not designed for regular use and store a relatively small amount of power. Jumper batteries are best for extremely small electrical requirements such as a cell phone or camera.
Not only do batteries come with different uses, there are also different chemistry makeups that affect function and battery performance. The two main vehicle battery designs that you will encounter are lead acid and lithium.
Starter batteries, deep-cycle batteries, and hybrid batteries can all be bought as either lead acid or lithium.
Lead Acid Batteries
Lead acid batteries have four internal parts: a positive plate, a negative plate, a separator and an electrode all contained within a case. The battery functions when a chemical reaction occurs between the two charging plates.
Flooded lead acid batteries (FLA): These are the most affordable battery type, but they also require the most maintenance. Flooded batteries use a standard liquid electrode which needs to stay topped off in order to operate properly. When purchased, these batteries are dry and come with removable caps so the casing can be filled with distilled water. The liquid level should be checked on a monthly basis and filled accordingly. Check out this website for details on how much to fill the battery and maintenance instructions.
Because flooded lead acid batteries are liquid they must be stored upright to prevent leaking their acidic electrode solution. They also have valves in place for off gassing. Flooded lead acid batteries release explosive and toxic gases as they charge so they need to be properly ventilated.
FLA batteries have a relatively long lifespan.
|FLA Pros||FLA Cons|
|Affordable||Monthly maintenance required|
|Long Lasting||Must be stored upright|
|Fast Charging||Needs ventilation|
|Works with most chargers|
Absorbed Glass Matt batteries (AGM): These batteries work in a similar way to FLA; as the name implies they use a glass matt instead of liquid electrode to separate the plates. AGM batteries hold their charge very well and are less sensitive to overcharging. These batteries are do not require dedicated ventilation because they have sealed valves that hold the gas inside unless severely overcharged. They were developed for the military so are quite robust.
AGM batteries are usually about twice the cost FLA batteries and generally don’t last as long. They are able to discharge and charge more quickly than FLA, making them more applicable in situations where quick discharge is needed in a deep-cycle application or taking input from a high amperage alternator.
Because of the design of AGM batteries, they do not need to be stored upright to continue to operate efficiently. In addition, these batteries require little to no maintenance. AGM batteries have many different nicknames and can be sold as dry cell batteries, non-spillable, or valve-regulated lead acid.
|AGM Pros||AGM Cons|
|No dedicated ventilation required||Shorter lifespan than FLA or Lithium|
|Holds charge well||More sensitive to overcharging|
|Robust (can operate at an angle)||Expensive compared to FLA|
|No monthly watering|
|Usually higher discharge rate|
Gel batteries: These work similarly to AGM batteries. They don’t leak because they use a gel instead of liquid electrode. Gel batteries are generally more expensive and more finicky than the other two chemistries. The gel inside can dry out and crack. They do have some characteristics that make them good for long term backup batteries and applications exposed to more extreme temperatures. For the most part we don’t recommend them for vandwellers.
|GEL Pros||GEL Cons|
|No dedicated ventilation required||Gel can dry out and crack|
|Handles extreme temps better||More expensive than FLA and AGM|
|No monthly watering|
When it comes to lithium batteries, there are a number of different types. The Lithium-ion batteries which are the little ones powering your cell phone (Lithium-cobalt) are different from lithium-ion batteries commonly used for deep-cycle applications. The ones we are specifically referring to are Lithium-iron phosphate (LiFePO4 or LFP).
LFP batteries break all the rules of lead adic. They can produce more electric power for a fraction of the weight and can be stored sideways or on a tilted surface because there is no liquid to leak. They are generally safe batteries, do not off-gas and are resistant to heat so you won’t see them blowing up like the type of lithium-ion battery powering the Samsung Galaxy Note 7.
|Lithium Pros||Lithium Cons|
|More power for a fraction of the weight||Expensive up-front|
|Can operate sideways or tilted||Newer tech leads to less options|
|Safe, no ventilation required||Charge controller needs to be programmed|
|Very low DOD (up to 95%)||Harder to find or replace|
|Faster charge than any other battery type|
Lithium batteries are advantageous because they can be discharged and stored almost completely empty without long-term damage. This means that instead of a 50% DOD limit (remember, that means using 50% of the total Ah capacity), you can design around a 90% DOD. They can also be charged quicker than lead acid batteries. Because of the way LFP batteries can discharge quickly but also deeply, they do have a specific type such as starter or deep-cycle.
Lithium batteries are the most expensive but also the most efficient battery type. They are one of the longest-lasting batteries on the market in both shelf life and charge cycles. If you have the money up front, they are more economical long term than Gel or AGM batteries.
LFP batteries also contain no heavy metals or acids and so are more environmentally friendly over their life cycle. It is possible to build your own custom lithium batteries which would decrease the price significantly. If you have the time and are feeling confident in your electronic skills, check out this article on custom building a lithium battery pack.
Overview of Battery Types
|Battery||Price||Maintenance||Ventilation||Healthy Discharge Limit|
(DoD - Depth of Discharge)
|Flooded Lead-Acid||$||Yes||Yes||50%||~500 cycles (2-4 years)|
|Gel Lead-Acid||$$$||No||Yes||50%||~1000 cycles (5 years)|
|AGM||$$||No||No||50%||~800 cycles (4 years)|
|Lithium Phosphate||$$$$$||No||No||95%||~2000 cycles (10 years)|
It is necessary to ventilate FLA batteries within confined spaces. Batteries will offgas while they are being charged. Be sure to keep this in mind when laying out your van build. The main design feature is to have a vent near the top of your battery compartment. This allows the lightweight hydrogen gas to float to the outside. Sulfuric-acid is the other main gas being released and is harmful to breathe. You don’t want the batteries to be off gassing under your bed as the sun is charging.
Some un-ventilated designs won’t ever have issues, and you may see some functioning designs without it, but it still should be done. You don’t want to be the lucky person who creates a spectacular battery fire!
Gel and AGM batteries are sealed and contain most of the gases inside so an external vent is not usually necessary; they just need atmospheric ventilation. This just means to not put them in a sealed container. We still would recommend not storing these batteries next to your head.
Continue reading to our battery maintenance post.
- Economical choice: Flooded lead acid. We like combining a pair of 6V Trojan brand batteries for optimum lifetime. They come in many sizes so often 6V is best. If you want to go bigger, get six 2V Trojan batteries for a huge bank!
- Low maintenance mid-range: AGM battery. This is what we’ve done because learning to maintain FLA batteries seemed like a good task to put off while we tackled other van building projects.
- Premium choice: Lithium batteries are just around the corner from taking over AGM in usefulness, but because they’re still fairly new they are harder to match components to and and source, plus the high up front cost is a barrier to many.
If you have specific questions for your setup we highly recommend joining an electrical forum to get more advice. We’re fond of the experts at www.solarpaneltalk.com and find they’re quite active in engaging discussion.