Technology

The correct battery for the camper expansion

Which is the correct battery for the camper extension? What are the differences, and what do you have to consider? In this article, we want to show you how to find the correct battery for your project and which aspects you should consider.

The correct battery for the camper expansion

Is there the correct battery for the camper extension? We believe there is no perfect battery unless your budget is unlimited. Every traveller has different ideas and demands for their trip and the consumers in the camper. The power requirements in the campervan can vary greatly. At the beginning of our world tour in Australia, we lived for two years without a refrigerator, solar and an extra battery. Our camper was very minimalistic and developed. To charge our laptops or camera batteries, we drove to a library and set up our cell phones while going or via a power bank. Nevertheless, we had an unforgettable time and experienced many adventures. It can be cheap!

But most of all, we missed a refrigerator or a cool electric box. Especially with the sometimes scorching temperatures in Australia, it was impossible to store cheese or yoghurt for a long. We don’t want to do without it almost seven years later. In New Zealand, we finally had a second battery and two portable solar panels for camping and were very happy to run a small fridge or charge our laptop.

When choosing a battery, ask yourself the following questions:

  • How long do I want to be on the road with my camper? Is it two shorter vacations a year, or do I want to travel by car and live in it for a more extended period?
  • Do I mostly want to be on campsites and use the electricity there, or would I rather be self-sufficient?
  • What is my power requirement? Do I want to be out and about in summer or winter?
  • How should the reserves be charged – employing solar modules while driving via the alternator or on campsites with shore power?
  • How much money am I willing to spend?
  • How much space do I have available, and what about the weight?

Power requirements in the campervan

First of all, you should calculate your electricity requirements. In connection with the desired time, which you want to be self-sufficient, this is decisive for the design of your system. We installed two 100 Ah AGM batteries in our Sprinter Van and thought this capacity would be sufficient for our project. In sunny weather, we had no problems. The solar modules on the roof constantly recharged our AGM batteries, and while driving, they were additionally charged via the alternator using a charging booster. But if it rained for a few days or we didn’t move for more than three days, we gradually ran out of electricity. Even if we drove for two hours, more was needed to recharge the empty batteries. This created a vicious circle that could only be broken by a long car ride or a day of sunshine.

Some campers install electrics in their van for €10,000, while others come out with less than €1,000. What matters most is how long you want to be on the road and which consumers are essential to you in the camper. A cheap and small battery is usually sufficient if you are primarily on campsites and use the shore power. If you want to stay away from camps and be on the road for more than a few weeks a year, then a 12V lithium battery (LiFePO4) can be worthwhile.

Our consumers in the campervan

  • 12V compressor fridge
  • pressure water pump
  • LED recessed ceiling lights
  • The mushroom fan in the shower cubicle
  • Diesel parking heater
  • 230V inverter for devices such as laptops, coffee machines, water heaters, mobile phones and camera batteries

Calculate power requirements

All electrical devices in the van consume a certain amount of electricity, also known as power consumption. This information can usually be found in the product description or on the back. This value is generally given in amperes (A) or watts (W). The electrical power (P) is calculated in the DC network from the voltage (U) times the current (I).

P = U *

Example: One of our LED recessed ceiling lights is specified with a power of 3 W.

Consequently, P = U * I becomes: I = P/U

So: 3 W / 12 V = 0.25 A

So the lamp draws 0.25 A per hour. Assuming that we use the light for around five hours a day, it has a theoretical consumption of 1.25 Ah per day; (5 hours * 0.25A). We have 10 LED recessed ceiling lights in total, but they are rarely all in use at the same time. Therefore we assume that we usually only use a maximum of 3 of them simultaneously, which means a total output of 0.75 A per hour, which then amounts to 3.75 Ah per day.

Of course, you don’t use the laptop for the same amount of time every day, but some consumers, such as the refrigerator, the water pump or the LED lights, have a similar daily consumption. Now follows a table in which we have inserted and listed our total daily electricity requirements. This makes it easy to maintain an overview and calculate different scenarios.

Only the 12V compressor refrigerator has a minor unique feature. This is specified with an output of 45 W, but the fridge does not usually run for a whole hour at a time, only for short on/off to cool down. We watched the refrigerator during our trip and noted how often it started up per hour on average. Of course, that also depends significantly on the outside temperature and how often it is opened. On average, the refrigerator’s compressor ran 1/4 of the time, so in an hour (60 minutes), it ran for 15 minutes. Therefore, its continuous output of 45 watts must be divided by a quarter. The compressor does not have a constant current consumption but, in the beginning, a very high one, which decreases after a short time (starting current). It is, therefore, difficult to state the actual consumption of the refrigerator.

For our calculation, we assume it is switched on 24 hours a day: 24 h * 0.25 = 6 h. Seen over a whole day, it runs for around 6 hours. Consequently, we calculate 45 W / 12 V = 3.75 A -> six h * 3.75 A = 22.5 Ah per day.

So we have a power requirement of around 73 Ah per day, which is quite a lot. To avoid lying to yourself when calculating, you should include the maximum helpful life. Otherwise, there will be a nasty surprise later. Our electricity requirements will probably be lower in normal everyday life and especially in summer. We use the laptops sparingly and usually only use the heater in winter or heat water.

This is what our wiring diagram for the electrics looks like. You can download our circuit diagrams here for free. Please note that despite careful planning, we cannot guarantee correctness.

Reduce power requirements

The power requirement table shows which components could be saved. The 230V devices usually have a very high current consumption via the inverter. On the one hand, this is because the consumers are generally more powerful and, on the other hand, to the efficiency of the voltage converter itself. When using the inverter, an additional 10% loss must be added. So you can save a lot of capacity by designing your consumers for 12V. For example, the espresso machine can be replaced with a gas-powered device such as a Bialetti espresso maker. There are also laptop chargers that can be operated directly via 12V. So you could save the inverter ultimately.

What types of batteries are there?

Wet battery (lead acid)

Wet batteries are among the cheapest, but they have many disadvantages. Gases are produced during the charging process, which must be routed out of the camper. The battery acid level needs to be checked and topped up regularly, and if misused, it can literally “boil” and leak. Due to its liquid acid, it may only be installed in an upright position. In addition, this type of battery can only be discharged up to 50% and has little cycle security.

Gel battery

With gel batteries, the electrolyte is bound in a gel, so they are leak-proof and primarily maintenance-free. In contrast to wet batteries, they can also be discharged more deeply. Otherwise, they are similar to a damp batteries in their characteristics.

AGM battery

AGM batteries are a further development of the gel battery and are often installed in campervans and mobile homes. Their sealed design means they are maintenance-free, spill and leak-proof. Nevertheless, attention must still be paid to the approved installation position.

They can handle slightly higher currents (like using a 230V inverter) and charge faster than gel batteries. However, they can only be discharged to around 50%, so you can never use their total capacity. However, when used correctly, AGMs have a long service life and high cycle stability.

Lithium battery / LiFePO4 battery

Lithium batteries are the new generation for campers, and apart from their high price, they have almost no disadvantages. You can compare them with a battery in a mobile phone. They have a high energy density with low weight and can theoretically be used up to the last ampere-hour. They easily tolerate high currents and are also maintenance-free. The battery can no longer be charged at temperatures below 0 degrees Celsius. LiFePO4 batteries are often equipped with a BMS (Battery Management System), a control unit. This control regulates all processes inside the battery and is usually also equipped with a Bluetooth interface, which allows you to keep an eye on the state of charge using an app. There are usually no restrictions on the installation position so that the battery can be perfectly integrated into the expansion.

We did a lot of research in advance and decided on the 300 Ah lithium battery from Wattstunden. On our next big trip, we don’t want to worry about our electricity anymore and still have enough capacity even on rainy days. At just 38 kilos, the battery weighs comparatively little. Theoretically, based on our calculated power requirements, we would be able to stand with the RV battery for at least four days without recharging. But since we usually don’t use that much and the battery is also recharged during the day via the solar system, we can certainly get by for a whole week.

It has a very high energy density – in the last self-build, we installed two 100 Ah AGM batteries. We could only use 50% of these, i.e. around 100 Ah, so we were often forced to charge the batteries after a few days. A 300 Ah lithium battery contains as much capacity as a comparatively 480 Ah AGM battery. So we more than doubled our battery power compared to the old build! Now we no longer have to do without the morning coffee from the espresso machine, and we don’t have to think twice whether we can fully charge the laptop battery today. The LIX300LT also has an integrated heating mat that heats the cells at temperatures below -5 degrees Celsius so that it can also be used on the coldest winter days. It can be removed when storing the vehicle over the winter.

Benefits of our 300 Ah lithium battery by watt-hour

  • High energy density with low weight
  • LIX300 LT – 300 Ah Lithium equivalent to conventional 480 Ah battery
  • One-to-one interchangeable with traditional lead-acid batteries
  • Up to 80% usable capacity without deep discharge
  • Built-in BMS with protection function for regulated energy flows
  • Integrated Bluetooth interface – keep an eye on the battery at all times
  • Number of cycles > 3000
  • Sealed maintenance-free battery

The only downside for us is the high price. LiFePO4 batteries tend to be very expensive, and you could buy a lot of lead-acid batteries for the money. But since we want to use our campervan full-time in the next few years, i.e. live in it all year round. Hopefully, this investment will be worth it for us. A lithium battery has a very high cycle stability so it can be used for more than ten years on average. On the other hand, an AGM RV battery is usually flat after two to three years. The bottom line is that investing in LiFePO4 can pay off with long-term use.

Conclusion on the battery when expanding a camper

There are many different batteries to suit all needs and budgets. The change in the camping industry is currently quite significant, and the offer is constantly growing. We look forward to testing our battery on the next big (world) trip starting next May and are sure that we will be able to travel flexibly and independently with it.

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