The rule of thumb says that Lithium needs about 50% of the capacity compared to lead-acid batteries. So I took 180Ah for GEL, AGM, and wet batteries because these are common battery sizes. However, there is no 180Ah LiFePo4, so I took the 160Ah.

• GEL cheapest, 2x 180Ah, $ 430
• The GEL of higher quality, 2x 180Ah, $ 750
• AGM cheapest, 2x 180Ah, $ 450
• AGM of higher quality, 2x 180Ah, $ 800
• Lithium homemade 160Ah (incl. BMS), $ 1700
• Lithium from Renogy Energy 160Ah (incl. BMS), $ 2350

Lead-acid cheapest 2x180Ah, $ 400 (from Exide, haven't found anything significantly cheaper from the cheap supplier)

Save money and build a lithium battery for the camper yourself

They exist, lithium kits. You can build one with some electronic talent and equipment and save a few bucks.

However, there are downsides. Balancers and BMS must be integrated into your motorhome electrical system. Chargers must be separated from consumers. With the dead LiFePo lithium batteries (at least from Renogy Energy), you have a BMS (BMS 12-200), which can control chargers and consumers bidirectionally via a single connection.

Incidentally, the question arises whether a self-made lipo has an E marking at all.

E mark (e-mark): This mark states that the device may be operated on land and in water in vehicles.

My main reason, however, is why I don't really deal with this topic in more detail: firstly, the cost savings are not that great. Secondly: if the mobile home catches fire and the self-made mobile home battery is the cause of the fire, your insurance company will pour you a Prosecco before laughing at you.

And anyway: In such a battery, quite high currents flow. As a layman, I've reached a point where I'd rather not tinker around with it. Even with my AGM RV batteries, I used pre-assembled cables, etc.

Of course, all calculations are very theoretical - it's just a standardized comparison, for a traditional mobile home, for standard mobile home residents, etc. In addition, it must be clearly stated that there is a lack of long-term experience with lithium iron phosphate as a mobile home supply battery. They have been running in our home for over three years. Nobody knows what will happen in ten years.

More Lithium, less solar power: 90% energy efficiency

The energy efficiency of GEL-acid batteries is at most 80%; usually, it is even lower. Especially when it comes to the last percent until full charge, it drops to maybe only 50%. It's completely different with the LiFePo4 battery: we're still at 90%. In plain language, this means: with a LiFePo4 battery. With alternator charging, you need fewer portable solar panels for RV.

Charge RV battery

• Solar system: a lot helps a lot - but it also weighs accordingly, and thanks to thousands of roof hatches, there is often no space for a lot of solar power on the mobile home. Your solar system should be calculated so that the built-in batteries (GEL or AGM) are fully charged by midday when the sun is shining. Then they can complete the absorption charge in the afternoon. With solar power calculator, you can calculate the optimal size of your mobile home solar system. The rule of thumb for lithium batteries is: the built-in solar modules should meet daily needs. With a lithium iron phosphate battery, you need about 1/3 fewer solar modules on the motorhome than GEL batteries.

• Battery charger: 220V from shore power - depending on how high this is secured and what the charger can do, your motorhome battery can be recharged more or less quickly. But, there is a but. GEL batteries should be charged to a maximum of 10% and AGM batteries to 20% of their total capacity. They can only tolerate more for a very short time. If the charging current is too high for these batteries, they also become confused more quickly - and do not become full because they think they are already full but are not. Lithium, on the other hand, can handle the more charging current. 50% is recommended. Here you can charge a 200Ah battery with 100A - until it is jam-packed. A 200Ah GEL battery requires at least 10-12 hours of charging time from 50% state of charge to 100% - and the regularly required absorption charging time again costs energy + time. A 200Ah lithium battery is charged from 50% to 100% in 1 hour.

• Alternator: A cut-off relay is installed in every mobile home to charge the built-in supply batteries while driving. However, this standard solution often does not bring much performance. Because in many vehicles, the alternator's voltage is too low, the charging current is more homeopathic thanks to long, thin cables. A charging booster can help. Charge the battery while driving with 45A. Depending on your travel behavior, this should already be a sufficient energy supply for your mobile home battery. So if you continue to drive 1-2 hours a day, you could even get by without shore power and solar power. At least if a lithium battery is installed - because the absorption time for lead batteries is longer, the AGM or GEL battery in the mobile home would never get full.

• Moppel, pinwheel, bicycle dynamo, mini thermal power station: Getting herrings into the mobile home battery will always be an issue. An interesting thing, especially for the tech-savvy hobbyist who is reluctant to drive to sockets. Do you often stand in a windy area? I have already seen some wind turbines on mobile homes. While solar naturally only supplies herringbones during the day, such a wind turbine could run overnight - and especially when the weather is a little bad, there is often wind, but no sun shines. And anyway, what exciting things will technical developments make possible? Lithium RV battery is relatively new. Graphene could be the next big thing, especially in solar technology - or something else entirely. It remains exciting.

Fast battery facts

GEL:
Charging characteristic: 14.4V
Overwintering/storage: fully charge, disconnect, every 1-2 months a charger for trickle charging
Quiescent voltage reached after approx. 5 hours
Maximum recommended charging current: up to 10% of the battery capacity

AGM:
Charging characteristic: 14.6V (Caution, not every (older) charger can handle this charging voltage)
Overwintering/storage: full charge, preferably a charger for trickle charging
Quiescent voltage reached after approx. 5 hours
Maximum recommended charging current: up to 20% of the battery capacity (from 10%, a temperature sensor is warmly recommended)

LITHIUM:
Charging characteristic: 14-15V
Hibernate/store: 50% full. Disconnect from all consumers and the BMS!
Quiescent voltage reached after 24 hours.
Maximum recommended charging current: Max. 50% of the battery capacity. No temperature sensor is required.

Which board battery should i buy now?

If money doesn't play a big role, you live in your mobile home for a large part of the year and want to have peace of mind regarding electricity for the next 10 years: Lithium.

If your budget is manageable, your travel and consumption behavior does not require an expensive auxiliary battery: GEL / AGM. For those on a tight budget: Search Google AND eBay for cheap no-name offers! For better quality, brands like Exide or Renogy Energy are recommended.

Even if it is a wet battery: mobile home batteries should always be sealed, cycle-resistant, and maintenance-free.

I would be suspicious of offers labeled as "solar batteries." There are no solar batteries in that sense. It's purely a marketing term. Especially here, you should pay close attention to the weight of a battery.

Benefits of LiFePo:
• More economical for "intensive" motorhome use
• Significantly longer service life compared to AGM / GEL batteries
• Less prone to handling errors (deep discharge, sulfation)
• Faster charging: tolerates significantly higher charging currents (alternator, shore power)
• The higher degree of energy efficiency: requires less solar power and charges fully quickly even when (almost) fully charged.

Advantages AGM / GEL:
• Lower purchase price
• More economical for "average" motorhome use
• Standard technology - can be installed/exchanged by any motorhome company, if necessary, even by yourself.

Power supply in camper vans: what is possible in 5-15 years

Automakers are starting to build battery factories - to mass-produce lithium batteries. An interesting development also concerns the supply battery in the mobile home. Will it become cheaper, or will there be more competition? Will the alkali metal lithium be mined on a large scale, making it more available and cheaper? Or an expensive, scarce resource? Batteries, in particular, are a hot topic worldwide. Research and development are being carried out, and billions are being invested - it's actually about storing electricity for electric cars and renewable energies on a large scale, but mobile homes can benefit from it. Energy efficiency, energy recovery, power generation, and storage - if we look at the development of the past 15 years, it will be interesting to see what is to come.

The self-sufficient mobile home is already no longer a vision of the future – but it is also not a bargain. A lot of solar power plus lithium batteries plus heating with a wood stove - a gas-independent energy supply for life in a mobile home is already feasible today. Well, fossil fuels will not be gone any time soon. The mobile home that runs on solar power is still a vision of the future. But wait, it's coming.