Modern lifepo4 batteries are a game changer for camping vehicles due to their ability to store much more energy than classic AGM or GEL batteries. There is a lot of discussion about the proper way to install the new type of batteries: going from "just swap" to "rebuild the electric wiring completely". The "just swap" position is probably right as long as the ampere hours of the new battery are not too far away from the old one. E.g. swapping a 90Ah AGM for a 100AH lifepo should be OK - as long as the size (esp. the height), the mounting and the type of generator in the motor fit (problem "intelligent generator). Swapping with a new 300Ah lifepo4 will probably require more work. First, the new battery - especially when close to being empty - can charge at a huge rate. This might damage the generator or could cause problems when the cabling is to thin. Second: such a huge battery needs a lot of solar power to charge and this will probably require new chargers, cabling etc. And that means you are suddenly going from a rather simple architecture with one main switch to something with many generators and with the positive and negative bus-bar in the center. Scale changes everything. This has nothing to do with your plans. It is simply the result of choosing a huge battery. If you stick with a small new lifepo4, chances are that you don't have to change a lot. But you also won't gain a lot from the swap. That means before you start thinking about technicalities you should define your goals: what do you want to achieve by swapping in new and powerful batteries? Are you simply going for an increased time away from regular camp sites and their land lines? A bigger battery and more solar panels and a new solar controller might already be enough. Or do you want to run a 230v air condition unit full time? Or do you want to swap out your gas range and install an induction range running on a high power inverter that also drives some other 230V sockets? Or are you going to be an autonomous van lifer living in a gas free camper? Your cable gauges and wiring will certainly change with your requirements. But whatever your final goals are. The basic architecture will probably derive from this one: At the center of your "star" are the bus bars, connecting several different generators with consumers. Do not forget the switches! see: DIN VDE 0100-721.They are sometimes required by the VDE for campers and they come in extremely handy in case of low temperatures (you might want to stop charging the lifepo4s when the temperature gets below zero) and maintenance (e.g. of the solar panels etc.). There is no longer a "main switch" and that means that you will have to think about the order in which you turn of generators. It is a bad idea to turn off the battery switch but leave the MPPT solar controller running. This will cause a floating level of power in your system and might damage consumers. If you spend a long time at a camp site attached to the landline: some chargers can provide regular 12.x DC for all the consumers. In that case turn off the battery and the other generators/inverters and live off the land line.

A few words on special topics. The so called electro-block (EBL) contains a switch that is driven by the so called D+ signal from the engine generator when the engine is running. Only then will the EBL connect engine and camper battery to allow charging of the camper battery when the driving. But most people will install a so called booster for this purpose, to either protect the engine generator or wiring from overheating (chose the new configurable ones from Victron, they don't get so hot) or because their intelligent engine generator would otherwise not recharge the camper battery properly (newer vehicles only). The switch in the EBL needs to be disabled and a new pair of wires needs to be run between engine and camper battery for the booster.

Another topic that causes a lot of confusion is the use of an inverter or a power station. If you plan to install one, now is the time to read: PERSONENSCHUTZ IM IT- UND TN-NETZ and Fachbeitrag: Elektrische Sicherheit für mobile Stromerzeuger. As long as you do not require more than one socket behind the inverter, everything is quite easy: you are running an IT-network without a need for an RCD (FI) or ground wire. The reason is simply that your L and N wires are not connected to the ground. But with more sockets you need at least one RCD (if you convert your IT net to a NT net (like in most houses) or one RCD per socket if you stick to the IT net. In both cases you will need a ground/earth wire connecting all the sockets and the inverter. The conversion to an NT net is usually performed by splitting the N wire and using one part as an earth wire going to all sockets. The RCD comes then after the split. If the L wire touches the case of a device that is plugged in, the power will flow from there through the earth wire - bypassing the RCD which notices the missing power and shuts the L wire off. BUT: once the landline gets plugged in, the RCD that protects the landline will immediately notice that N and earth are connected and will turn off power. That means that there needs to be a relay that connects N and earth in case there is no land line and disconnects both wires when there is a land line. The land line gets priority (in german: "Netzvorrangschaltung"). The good news is that recent inverters for motor homes already include those features. Just follow the manual. If you think: what the heck, I don't need that crap. It's only 12V that drive the inverter - think again. 12V * 200Amps is 2400W. 2400W / 230V is a whopping 10 Amps!! Scale changes everything!

OK, one last word of caution: many cheap inverters from China have two sockets. In most cases you have no knowledge about the circuits inside. You can't even assume that the inverter has complete galvanic isolation (e.g. through a transformer). Some want an extra connection to the ground, some don't. You can only hope and assume as litte as possible. For now I'v decided to use just one socket.

For many people the correct selection of a MPPT controller (solar controller) is a problem. How many volts, ampere and watts are needed? Well, that clearly depends on how powerful your solar panels are AND the way you want to connect them. Please take a look at the Victron book below for some possible ways to do so. The book also explains the dependency between volts and ampere in you installation: a serial connection drives up the volts, a parallel the amperes. A parallel installation is better when there is a frequent chance for partial shadows on your panels because if one panel is in the shade, the other can still deliver power. BUT: your cables need to support the amperes!! the book will tell you how to calculate cables but it does not tell you a little trick: if you go for high voltage panels (e.g 36V and up) and connect them in parallel, your amperes will go up but not as much as with 12v panels. I have chosen the Victron 100/30 which would support 100V and delivers 30A to the battery. It supports 440W at that is exactly the power from my modules. The amperes from panels to the controller are roughly 10A and that still fits my cabling nicely. With low-voltage panels I would have had to upgrade my wiring.

Now it is time to get down and dirty with the installation. I urge you to read the book "Wiring unlimited" by Margreet Leeftink first. There is also a german edition available. It will tell you all about cable sizes, connections, tools etc. The higher you go with the amperes, the more critical becomes the wiring. For the really big motor homes the only reasonable choice is anyway to go to a 24V or 48V installation to reduce the danger. But stretching 12V systems to support 3000W inverters is a risky business. 3000/12V means 250A will flow through the wires. A rule of thumb (the book has more detailed formulas) says, that for short distances you can divide the amperes by 3 to get the mm2 needed. In this case we are around 85mm2 for the copper wires to the inverter. Assuming a distance no longer than 1 or 2m between battery and inverter. Keep distances as short as possible. In extreme cases the position of consumers and generators on a bus bar should be taken into account and kept as close together as possible. One last scare: lets assume 2m of copper cable 70mm2 and 250A. The resitance is 0,017 * 2 / 70 == 0.00048Ohm. The formula to calculate the power loss is P = Ohm * ampare squared. In this case we experience a loss of 30W just within the cable. Now imagine a bad connection at the bus-bar or at the inverter resulting in an extra 0,001 Ohm. The loss is now 0,00148Ohm and multiplicated with 250A squared we get 92.85W!! This is called a fire hazard! If you plan to build a gas-free camper with induction range etc. I would recommend at least a 24v installation.

A few words about the installation cost. You need decent crimping and measurement tools (hydraulic, with pliers etc.) and you should ABSOLUTELY not try to save money on the installation material. For the reasons given above. You should calculate for materials like cables etc. at least 500 Euro. And when you buy bus bars etc.: Go an measure the cross section! you will find stuff that says 250 amps on the package but comes with a very thin metal plate - often not even using copper. Forget your old crimping tool used to connect some wires on your car radio. It will not do. And watch out for the wiring sizes supported on your devices! Most smaller victron devices support max. 16mm2 cables!