- Jimmy Sutjak
What size and type of batteries for you camper van build
Determining the size of your solar system is an important first step in building your off-the-grid adventure rig. The limited available space and weight capacity of vans is just one factor in determining the size of the solar system. Cost, for most people, is yet another limiting factor. The features of the system each have unique power requirements and also determine the amount of power that is entering the system.
Determine power requirements
The first thing that you have to decide is what features you want to have on your camper van. This includes refrigerator, water system, water heaters, cabin heaters, fans, lights, and anything else that you want to add that will require electricity to operate. This is an important first step because you will then build off of these energy consumption requirements.
You can start in two different ways. One way is to design your ideal build with the maximum amount of features that you want. In this way you will then be able to determine the maximum amount of energy that is required to power your system. If the system is too large and/or too expensive, then you can begin to cut the things that are nonessential. In this way you can also plan for upgrades in the future, without having to completely rebuild the system. The alternative is to start small and modest, only adding the features that you need or want the most. You can then incrementally add the features that you want until you reach your ideal size-to-price.
Next, you want to look at the power requirements for all of the devices that you plan on powering. Each device is unique, so you want to make sure that you lookup the specific power requirements of the devices that you will be using. This should include everything that uses electricity and should be estimated for the length of time that the device will be utilized. Ultimately, you will want to determine how many amp hours (AH) you will need to power your system.
During this step there is one equation that you will become intimately familiar with in order to determine your power requirements for your system. Amps = watts / volts or Watts = Amps x volts. You can then multiply amps or watts by the amount of time that the device is running in order to get an estimate of the amount of amp-hours or watt-hours being used over time. Typically, batteries used for solar system builds will list the amount of amp-hours (AH) stored in the battery.
How do you use this formula to determine the amount of power that you need in you solar system?
Suppose you are looking at mini-fridges and you are trying to determine which refrigerator you should use in your system. You can go out and look at the energy rating of the refrigerators in order to compare the usage. They will tell you their energy usage in one of two ways, watts or amps. A 2.4 cu. ft. refrigerator such as the ones that we use in our van builds use approximately 100 watts to operate. The fridge will typically run for about 8 hours per day. 100 watts x 8 hours = 800 watt-hours. For this particular type of fridge the voltage is 115 vac, or the normal wall power in the USA. This can be translated into amp hours with, 800 WH/ 115vac = 6.9 AH
Alternatively, some manufacturers will tell you the amount of amps. For this size refrigerator the amps is approximately .8 amps. Again, this will be running over approximately 8 hours, .8 amps x 8 hours = 6.4 AH
6.4-6.9 AH is the estimated energy usage of this refrigerator over 24 hours. A few things to consider is that the refrigerator draws much more power for a few seconds when the compressor kicks on. Preventing the compressor from repeatedly kicking on and off will reduce the energy usage. This can be achieved by keeping the back of the fridge well ventilated as well as keeping the door closed as much as possible.
In a camper van solar system, the majority of components are 12v dc power. Anything that is run on 110v needs to run through am inverter which changes the 12v power to 110v. In this process, energy is lost. As a result, running any 110v device will inevitably draw slightly more power than is listed on the device. This should be considered while deciding between110v or 12v as well as when you are calculating the size of your system.
The 24 hour energy usage should be determined for each device in order to come up with your basic battery size. This total number is only an estimate and the power usage can differ depending on the climate, time of year, hours of daylight and much more. Additionally, if you are planning to travel in areas where your solar panels will not receive enough sunlight everyday to fully power your system, then you will have to add stored power to your system to get you through those rainy days. Larger batteries will in turn require more solar panels or another source to fully charge the added capacity.
Differences in batteries
The two different types of batteries that are commonly used in camper van solar systems are Lithium batteries or ABS deep cycle gel batteries. The major differences are price, efficiency, and longevity. The Lithium batteries cost much more than an ABS battery, but they last longer. Additionally, lithium batteries can use almost 100% of the amp-hours whereas ABS batteries only use half. This means that a 100 AH lithium battery is equivalent to a 200 AH ABS battery. A 200 AH ABS battery only has 100 AH of useable energy.
Maybe this is a good point to reassess what things you want to run off of power as opposed to what things you can replace with a mechanical system that does not require electricity. There are hand or foot-powered water pumps, for example, that do not use any electricity and work perfectly fine for washing dishes. The downside is that they do not offer the same comfort and added ability to shower or rinse off your gear.
Battery power is what will run all of your devices unless you add some sort of shore power in order to connect directly to the power grid. In all of our builds at Alpinvan we use 200 AH ABS batteries for the basic build. These systems have adequate power to energize all of the devices and even has enough stored power to get you through rainy days, especially in the Pacific Northwest. Your next step in building your solar system is to design your solar array and any additional methods of charging. Solar panels are an inevitable first step in getting your system recharged off-the-grid. but these can also be supplemented with other things to recharge your system. Read our next post in order to complete the perfect solar system for your camper van.