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By Jon Winge
Caravan and Caravan magazine, No. 1 February 2022

Here's what you need to know: The ideal camping battery

It is no longer necessary to carry around an excess of lead to get current in the rolling arc. More than we are used to too! Abra kadabra – hocus pocus – sim salabim. For 120 years, the world has been waiting for new technology to store electrical energy - and then it happened, almost as if by magic.

The element lithium with atomic number 3 is a very light metal that is more than happy to react chemically. It is found in large quantities, is not toxic and is therefore particularly suitable as anode material in rechargeable batteries. There, lithium ions move back and forth between the negative electrode (anode) through an electrolyte (a conductive medium) and the positive electrode (cathode). This is how we can store or extract electrical energy. The great advantage of this chemistry is that the components are light, unlike lead, but above all that the reaction is powerful and (almost) stable. Lithium-ion batteries (LIB) are a giant leap in energy storage and suddenly make battery operation highly topical in a number of new areas of use. The closest thing is electric cars, but consumer electronics have also made great leaps thanks to LIB.

Then there was the environment, then…

Lithium in batteries is not without problems either. Let's get back to it and rather start with the good: Lithium is found in large quantities, it is not toxic, and extraction and processing are significantly more environmentally friendly. The disadvantages appear in the elements used in the cathode material (the other "pole" in the battery). They have an unfortunate environmental footprint. LIB batteries in consumer electronics and in electric cars use, among other things, cobalt, nickel and manganese.

  • LCObatteries (LiCoO2) with cobalt oxide is used in cheaper consumer electronics.
  • NMC-batteries (LiNiMnCoO2) with nickel, manganese and cobalt oxide is used in most electric cars and is also taking over in smart phones and laptops etc.
  • NCAbatteries (LiNiCoAlO2) with nickel, cobalt and aluminum oxide are currently the best in terms of energy density and fast charging/power output (Tesla), but they are the most expensive.

More types will no doubt come as the requirement for range (amount of energy) increases.

Fire hazard

At the time of writing, firefighters are complaining about the many fires that occur in electric bicycle batteries. If the battery in, for example, a Tesla burns, it cannot be extinguished until the process has finished, and the smoke is toxic. However, the probability of this is minimal if the correct management systems are used. So it is not the lithium itself, but the metals "on the other side" of the battery that are scary. But there are several roads that lead to Rome – and there are several substances that can be used in conjunction with lithium. The latest big thing (which we've had for a few years, but which is now really breaking through) is the combination of iron (ferrum – Fe) and phosphorus (P), i.e. lithium-iron phosphate LiFePo4. The cathode in such batteries is usually porous carbon (graphite). This battery chemistry is called LFP

Safer and cheaper

LFP is almost as efficient as the rest (marginally lower energy density and output), but the big advantage is that the process is much, much safer and more environmentally friendly. The price of the batteries will also be lower over time. Today you can get LFP batteries for about the same price as the most expensive and best lead-acid (AGM) batteries. However, the advantages are several: The LFP battery weighs around half of lead batteries. While you only have access to half the capacity of the lead battery, you can enjoy almost 100% from the LFP.

High current can be a problem

The oldest LFP batteries were thus unusually efficient. They were therefore viewed with some skepticism, especially by manufacturers and retailers of rolling camping homes. That is in itself logical, because the new batteries actually require more of the electrical installation. The LFP battery has little internal resistance and can therefore receive more current (amps) than the lead battery. This can cause problems in electrical systems that are not designed for this. Undersized components can overheat and even burn. The same applies to thin wires.

Particularly vulnerable are old couplings which may not be tight enough, or which have even become corroded/worn. Old dynamos of the "not smart type" can also have problems because the battery requires so much power. The result may be overheating, but I have not heard of alternator fires for that reason. In newer motorhomes and caravans, however, most of this is already OK.

Plug and play?

In modern camping vehicles, it is mostly just a matter of replacing the old lead battery with a modern LFP battery. They come in many versions, and many of them have "drop in dimensions". The most common household battery is around 100 Ah (ampere-hours), and you have plenty of room for that. And it will also give you twice as much power as you are used to - with half the weight. If, on the other hand, you want more power and less weight, you should consult a professional.

LFP requires reliable monitoring

The battery monitors itself with (Battery Monitoring System). An LFP battery happily handles 150 A current, maybe more - both in and out. That means a full battery in less than one hour. However, fast charging is not healthy for any battery. It is best if a charging current does not exceed 50 – 70% of the capacity continuously. With a normal LFP residential battery, that means 50 – 70 amps, and that's still a lot! This is a rule of thumb. The values ​​vary, so check the specifications of the individual brands. In any case, such a large current requires thick wires and good connections. The residential battery is usually connected to the starter battery by a charging relay or a battery isolator that prevents the starter battery from being discharged. A charger relay should now be able to withstand 120 A. If the motorhome or caravan has a normal 35 A relay, it should be replaced. The old one must be disconnected completely.

From lead to lithium?

It is usually easy to change, but you should know this: the LFP battery must have monitoring - BMS - preferably with Bluetooth. Then you can read how much power you use and how much you have left on the battery with an app, as described in the previous edition of Teknikkhjørnet. Make sure your new battery has this. LFP differs from lead-acid in that the battery maintains a constant voltage during discharge (see more about the smart dynamo below). If the charger cannot handle this, the battery will not be fully charged as we should expect. The almost constant voltage over the entire course means that we can no longer use a voltmeter to see how much current is left on the LFP battery.

Have to trick the dynamo

"Antli-sulphating chargers" with "equalization mode" use voltage spikes to release sulphate ions from the lead plates (a dubious solution, because what remains on the plates is usually already crystallized sulphur, and then nothing helps). This happens at a voltage above 14,6 volts. It may damage the LFP battery. Older motorhomes and caravans that have chargers from Italian CB - e.g. The CBE5xx needs an additional charger, according to Skanbatt. Old battery chargers do not work well. Most Euro 6 engines have a so-called smart dynamo, which is not really very smart. It delivers variable voltage instead of constant current. It is a good fit for the starter battery, for which it is intended, and it is a bad fit for the living room battery. The voltage at start-up is indeed high, but it drops quickly, and it runs out of charge.

The DC-DC charger

The residential battery must therefore have a high enough voltage to be fully charged, but the smart dynamo does not offer that. The battery is starved and weakened. Ultimately, it will be damaged. We solve this problem with a modern DC-DC charger (direct voltage to direct voltage). It monitors the living room battery, compensates for any voltage variations and ensures fast and safe charging. It therefore stabilizes the charging voltage and protects the battery, electronics and other electrical equipment. Traditional solutions for charging consumer batteries often need a few seconds to activate. The DC-DC charger starts immediately. This is particularly important in a car that has both a smart dynamo and a start/stop function. The DC-DC charger is therefore the battery's best friend. It maximizes battery life and ensures that it is always fully charged. It is standard in newer camping vehicles. Check in your own and retrofit if it has an old-fashioned charger.

Voltage suppressor

Some electronic equipment requires a high starting current. In some cases, this can cause the BMS function to switch off. Certain batteries (e.g. Skanbatt) are therefore supplied with a function that prevents the battery from being "switched off" at a high short-term current (peak). The new "peak damper" should allow the batteries to handle significantly higher, short-term current draws without the BMS shutting down. I myself have never experienced this problem with my increasingly old LFP battery, but you never know...

HEAT function

Older lithium batteries can hardly withstand charging in the cold. If it approaches freezing, LFP batteries only tolerate a charging current of up to 5 amps. (See previous issue of Teknikkhjørnet).

However, new versions have an integrated heating element. When the battery requires a lot of current due to low capacity, most of the charging current goes to the heating foil at the start. The battery heats up before it gets a full charge. This is controlled by the battery's BMS. The foil does not draw power from the battery, only from the charger. The heat function varies somewhat from battery to battery. Some have a BMS that activates the heating foil at the same time as they receive full charging current. Then it is still risky to charge in freezing temperatures, for example if you start the engine and the alternator gives full power.

LFP battery life?

Good lead-acid batteries should have a lifespan of at least six to eight years, depending on the type. However, most only live for three or four years, according to users of motorhomes and caravans. It is due to nothing but incorrect installation and, above all, poor living conditions. My own experience over five years with one and the same LFP battery of 150 Ah with BMS, but without Heat, is that it is exactly as robust. I expect it to continue like this for at least another ten years! A lead-acid battery can withstand perhaps 500 cycles, good types significantly more. This means that it has received and emitted its full capacity (number of ampere-hours – Ah) ​​so and so many times. In good condition! The LFP battery has an expected life of 3000 cycles. In practice, it means far more than you will experience, almost regardless of how much you use the camping vehicle. In addition to much more power and significantly less weight! It's good economics, that.

Why not lithium as a starter battery?

The large current – ​​both ways – should make the LFP an excellent starter battery, but no; After all, the BMS monitors the current both out and in, and it is limited to 100 - 150 A. The starter motor can quickly draw 2-400 A at the moment of starting. Then there will be too little "puppet" for the self-starter, unfortunately. Otherwise we would see a revolution there too.

What do the dealers say?

We are in the midst of a technological shift, and that leads to healthy skepticism among importers and retailers. The fear of ending up in a warranty liability is naturally present. Several dealers, however, retrofit LFP batteries without further ado - there are thousands of such batteries on Norwegian roads today, some also offer LFP in new motorhomes and caravans. This is how a selection of players in the caravan industry answer questions about retrofitting lithium batteries:

Leisure farm, Bergen, Polar, Solifer, Pössl, have retrofitted lithium batteries and know of no problems.

The camping farm, Lierstranda, Rapido, Adria, Itineo, do not install LFP batteries without approval from the manufacturer, who correctly points out that the wire cross-section and charging system must match - which is not always the case in older models. They have, however, done two trial installations and are following along well.

commuter car, Stavanger, Banimar, Autostar, Malibu, Auramobil, Pössl, say that their brands are currently not supplied with LFP batteries, but that this is not due to technology, but costs, and that some motorhomes even come without a residential battery. Then it is up to the customers to decide. They very often supply LFP batteries, and on the Autostar Prestige this is standard. They have not experienced any problems.

Solar Car, Sola, Pössl, Aura Mobil supply the vast majority of cars with LFP batteries. For Pössl, they strongly recommend LPF.

Ferda, various dealers of, among others, Dethlef, Kabe and Sunlight, are exclusively positive and say that Dethlef and Kabe will come with LPF as an option in 2022. It currently looks as if Knaus will also launch this. Knaus has previously said that their models are not adapted to LPF, but here the development continues.

Solid Import, earlier Hook, has not responded to the inquiry. However, they have good knowledge and can therefore advise customers.

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