Monday, 22 September 2025

Lithium in the Classic Hymer in 2025 - no real reason not to - and busting the myths about Lithium.

First draft - Sep 2025

NOTE BEFORE READING. What follows may appear to be personal opinion, but I assure readers and owners that I have done a lot of research and had conversations with many others, both amateur and professional. I have also made many hours of actual physical experimentation and have installations out on the road in daily use. I have also made copious use of AI to check basic technical facts, and also to summarise and analyse years of social media and technical forum comment. I am happy to engage in friendly discourse, as always.

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You can now buy a 100ah smart Lifepo4 with Bluetooth for £200 or a bit less. This means that the price is now only about £50 above a good quality lead acid battery. 

For the extra £50 you get a battery that will last at least 10 times longer and will give you at least 50% more usable power. But most importantly, you will get a battery that will talk to you! This is the "smart" part of the name - unlike a traditional lead acid battery, smart lithium batteries have a brain which monitors the battery and it will talk to you via an app on your phone or tablet.

This is the most important and powerful feature for motorhome owners - information. But be warned that not all 12v lithium batteries are smart with Bluetooth, so make sure you see Bluetooth in the specification. 

Once you have a smart lithium battery in your van and an app in your hand, you then get to know everything that is going on in your battery system. The brain in the battery, known as a BMS - battery management system - tells you exactly what the voltage is, and how many amps are flowing in and out and how many you have left. For a motorhome owner, this information is invaluable because it puts you in control with no more nasty surprises. In the old days you never knew how much power you had left until the lights went dim. Now all you have to do is look at the app.

So why doesn't everybody rush out and buy one? 

The answer is complicated. It is a combination of fear of new technology, a belief that it is expensive, and whole raft of internet memes and stories preaching doom gloom and confusion.

Fear of new technology is reasonable - it has always been so. There is always an adoption curve with a new technology, and there are always geeks and early adopters who can't wait and get in first - they pave the way for the rest of us. In the case of lithium batteries for motorhomes, I now firmly believe that they are now in the mainstream, and that lead acid batteries are now "old technology".

It is the same for the money side. Lithium used to be 10 times the price, and now it is not. The reasons for this are simple - electric cars and China. The batteries are now being churned out in such huge quantities that the prices have plummeted. The lithium battery market is now even bigger than the old lead acid battery market, because the lithium batteries in electric vehicles are far bigger than the old fashioned starter batteries. 

But the doom gloom and confusion question is a lot harder to answer - harder, but certainly not impossible. I have been monitoring the situation for many years and my conclusion is quite simple - bad news travels fast on the internet, good news does not. What has happened is that a few stories from the early days have become internet memes, and the biggest of these is that "lithium batteries can't just be swapped for lead acid batteries", and worse, that they "will cause damage".

But these stories are not just made up out of thin air - there have been negative stories from the early days of lithium, but as with many other stories online, they have grown in the telling, been embellished, adopted by armchair experts, and then quoted as fact. The trade have also played their part, and adopted their arguments either to preserve their existing business by doing down new technology, or promoting it as "must only be installed by professionals". The rest has been a huge amount of confusion and hearsay - no wonder the average owner gets confused.

Unfortunately to explain all this away I now have to get into technical details, but I will try and keep it simple.

Let's take the damage side first - where did these stories come from? They came from the press coverage of several major incidents in recent history. The most famous of these were the battery fires in the new Boeing 787 in the first year of its life, the crash of a DHL cargo plane that was blamed on a consignment of lithium batteries and the famous case of the Samsung phones catching fire in your pocket. And we can all add to these the many stories we see online of electric cars on fire. There are plenty of other stories too and the collective belief has become - lithium is dangerous. And the actual truth is - yes it is! But only if badly handled. But you also have to remember that there are several types of lithium battery and they all have different characteristics. In response to the early problems, there was a scientific race to improve the safety of lithium batteries, and the result was Lifepo4. This stands for lithium iron phosphate and is the safest type of lithium battery ever made, and is the only type used in leisure vehicle applications. And it is very safe - safer than lead acid in most respects. But the old stories still linger that "lithium" is unsafe.

The other aspect of the "damage" memes, is two sided. Either that you will damage your old lead acid setup if you just drop a Lifepo4 battery into it, or that the battery itself will be damaged if you do.

Let's address the last one first. It is just wrong. A Lifepo4 battery has a BMS and the purpose of the BMS is to protect the battery. It does this by monitoring everything, non stop, in real time. If it detects anything outside of the ordinary, it simply shuts the battery down and isolates it. Overcharge it, it shuts down, over discharge it, it shuts down, too hot or cold? It shuts down. In fact it is just about impossible to damage a Lifpo4 battery with electricity or temperature - it just shuts down, and stays that way until the problem goes away. And helpfully, because it is smart, it will tell you via the app why it has done this, which is a great aid to troubleshooting. 

So why the myth? I believe it is because of the first aspect, that damage to an old setup can be caused, and that damage has just been expanded to mean any damage. So let's move on to the question of damaging an old lead acid setup by just changing the battery from lead acid to lifepo4, and nothing else. 

The maximum charging voltages of both battery types is 14.4 to 14.7v. In reality, charging systems in a classic motorhome are generally around 13.8v to 14.4v - so there is no danger there, and don't forget, if you did drop a Lifepo4 into a system that had a (faulty) charging voltage in excess of this - guess what! It would shut down - unlike a lead acid battery that would get hot and start to fizz and smell - and there are plenty of internet stories about that.

So there is no danger the a Lifepo4 battery it is protected. So what about the other components in a motorhome setup - the charge sources. There are 3 charge sources in a modern motorhome. The alternator, the 230v EHU charger, and solar, if fitted.

But before we progress to discussing each of these in turn, let's address the one area where a Lifepo4 battery is different to a lead acid battery - it has a lower internal resistance. This means in simple terms that it is capable of taking more charge and will take that charge until it is full - which means that it will charge quicker. In many respects this is a good thing for a motorhome owner. You want your battery to recharge in as short a drive as possible, or to take full advantage of sunny weather, or a quick plug in to EHU.

But while this is generally a good thing, it also has a down side, and this down side particularly manifests itself in old classic motorhomes, because in many instances, the equipment is old - the alternator, the EHU charger, the solar system - they could very easily be 30 or even 40 years old. So what happens is that sometimes, but it is by no means definite, when you swap a lead acid battery for a Lifpo4, some of the components might suddenly be asked to work a bit harder, and occasionally this extra work might be the final straw that pushes an already tired component over the edge and into failure. And what happens then? The latest change gets the blame - the new battery. And because bad news travels fast on the internet, before you know it - it's "lithium battery killed my charger", or alternator, or whatever.

But there is no technical reason behind this - all that happened was that the charger was ready to give up anyway. Or the alternator, or the split charge relay, or the main fuse that you didn't even know was there. But it wasn't the battery.

Everything is old in a classic motorhome. Long before lithium came along, these situations were common. Take chargers as an example - pre 95 Hymers left the factory with 10a chargers and 100ah lead acid leisure batteries. As the vans got to 25 years old these were famous for breaking, and many were replaced. In fact it is quite rare now to even find an original still installed. But they are perfectly capable of charging a Lifepo4. I have taken original chargers and put them on my workshop bench connected to Lifepo4 batteries and tested them for days and weeks. 

Same for alternator charging. The original classic Hymer split charge relay system is designed for 20 amps - that's why the Strom meter on the panel only goes up to this figure. And it is all that the cabling and relay system is capable of carrying. Hymer designed it this way. Most classic Hymer alternators were only about 60 amps or so, so you don't want too much additional load. With headlights on and the wipers going full tilt, pulling away from a festival on Monday morning with an empty leisure battery - that's when the 30 year old alternator finally gives in and shouts "enough!"

So the point I am trying to make is that these stories derive from old age and circumstance, and can be rarely if ever be blamed on the battery, whether it be Lifepo4 or lead acid. Nothing lasts for ever. 

So what to do? How can you be sure? The answer comes free with the Lifepo4 battery - it is in the box! When you have an app in your hand that tells you exactly what is going on you can identify potential problems in advance, and be ready for them. Here are some practical examples. Let's say you have the original 10a charger and you install a 100ah Lifepo4 battery. You can run a test - with nothing else connected, plug in the van and see how much power the charger delivers to the battery - the app will tell you exactly. In most cases you will not even see 10a - because the charger and cabling may be old and tired. Same goes for the alternator - you want to see about 20a - the app will tell you. Ditto for solar.

This information will inform you and enable you to make decisions. 

Finally I want to address the other online meme about Lifepo4 - that you have to change your charger, fit a 2b (battery to battery charger), or change your solar controller because the old one does not have a "lithium profile". A lot of this is based on the fact that when somebody goes online and asks the question, somebody has to answer. And the most plausible answer is the one that advises you to "upgrade". So people do! But for a basic installation it is usually not necessary.

However there is one instance where this advice is sound and that is when you want to install biggeer batteries. There is a lot of fun and pleasure to be had from messing with motorhome electrics. And one of the great advantages of lithium is that it is capable of packing a lot of power in a small space. 200ah, 300ah and even more, are now affordable and capable of being installed in classic motorhomes. This gives owners the chance to run high power stuff like hairdryers, coffee machines, toasters, kettles and air fryers ... and many do. But if you do increase the battery capacity of your motorhome beyond the original 100ah, you can, but then of course it follows that your charging systems also need to be upgraded - not for any technical reason, but for practical reasons. Every amp you take out has to be replaced, so you want to do this as fast as is practically possible. This is where the stories come from - it is not that you "have" to, it is that you "should" because it makes sense. You can in theory, safely charge big batteries with the old setups - but it would just be too slow!

But everything in an old classic is delicate, so when you are trying to get more power into a battery, these things have to be carefully considered. Some of the decisions are easy, such as installing a bigger charger. Same for solar - install bigger panels, and if you are upgrading panels, then you will be buying new modern controllers, and these will have lithium profiles - no brainers. And in the case of old alternators where you don't want to overload them, the advice is generally don't try to pull more than about 50% of the alternator power to charge a big leisure battery. And the easiest way to do this is to install a b2b of the required capacity - there are other ways, but a b2b is the easiest, and if you have just spent £600 on a big battery, you can afford a b2b at £120 ....

But if all you are doing is replacing an old 100ah battery with a new 100ah Lifepo4, you can, just make sure it is smart, with Bluetooth, and that after you install it, use the app to keep an eye on it. And in pure classic Hymer terms - the pre 95 models - there is no reason why the original charger and relays can't cope with a Lifpo4. If you do have problems, it won't be the battery's fault - they were bound to happen sooner or later anyway. You can't damage a Lifpo4, and Lifepo4 is a very safe battery technology. Any problems you do have are easily fixed. 

There does happen to be a "sweet spot" for a higher power classic Hymer lithium installation. In terms of the space available for the batteries, the space on the roof, the way the cabling is set up ... I call it a "quad 3" setup. Most roofs will take 300w of panels - the front part of the roof will take a 1500 x 1000 300w panel perfectly, unless there is already a small rooflight there, over the front bed. Victron make a lovely high quality 30a charger - also bluetooth, and I have fitted more of these than any other. And with most alternators being around 60 to 80a - then a 30a b2b charger is just right. And a 200a or 300a Lifepo4 battery can be made to fit in most vans. So all these numbers have a 3 - 300ah of Lifepo4, 300w of solar, 30a charger and 30a b2b. This makes for a well rounded and versatile system. It will support a 12v compressor fridge, which is becoming a popular upgrade. It will support an inverter that will power those desirable coffee machines and airfryers. It will make the most of the roof space, to maximise solar energy, and give you the most you can reasonably expect from your engine and each hour of driving, and a 30a charger will give you a full battery from empty on just an overnight charger, minimising the time that EHU is needed. Such a "quad 3" setup at 2025 prices should cost no more than £1000 (not including inverter) - and that is using all Victron. This can often be reduced considerably if existing or cheaper gear is used. 

And a final note for post 95 van owners who are saying "what about vans with a EBL?" .... the short answer is - pretty much the same - there is no reason for you not to have exactly what you want - a 100ah smart lithium will work with an EBL, and for bigger battery setups, the EBL can be bypassed and just used for 12v distribution. I have done many of these, but there are 3 or 4 different EBL models and each has different requirements, so to write an article that covers everything would be long and confusing. I have diags and ideas for most EBLs so best to contact me or ask on the group.



A typical smart battery app - information is power!











Tuesday, 19 August 2025

The Truth About Hymer Habitation Door Hinges: Myths, Fixes, and Simple Solutions


The Truth About Hymer Habitation Door Hinges: Myths, Fixes, and Simple Solutions

NOTE - This article is AI generated, but based on real world info, and edited and checked by me.

For owners of classic Hymer motorhomes made up until the mid‑1990s, one of the most common headaches is the habitation door hinge. These aluminium hinges, after decades of use (and often years without proper lubrication), are prone to seizing up or snapping outright.

For years, motorhome owners have shared stories of broken doors, expensive replacements, and various "solutions" ranging from plastic 3D‑printed hinges to hand‑machined aluminium reproductions. But Ron Bentham – a former metalworking engineer and long‑time Hymer owner – argues that none of these options are really necessary.

In fact, he insists the fix is simple, affordable, and reliable.


Why the Original Hinges Fail

Hymer’s habitation door hinges were originally aluminium extrusions. Over time, exposure to the elements and lack of lubrication leads to the hinge pin seizing in its socket. Once this happens, the huge leverage of the habitation door works against the seized joint, and the brittle alloy hinge body cracks or snaps.

Ron warns that many owners don’t even notice their hinge has seized until it’s too late:

“If your door moves, but stops dead when you stop pushing – instead of swinging freely – then a hinge has seized. That needs emergency attention.”

When a hinge does crack, most people choose replacement — but it isn’t the only option. Being aluminium, hinges can sometimes be repaired by a skilled metalworker with aluminium welding facilities (often a case of who you know rather than an everyday retail solution). In less severe cases, owners have managed to extend a hinge’s life by drilling extra screw holes for fresh fixings, or fitting a large washer to spread the load.

Different owners have different levels of skill, tools, and facilities — so while repairs are certainly possible, replacement remains the easier route for most.


The “Special Hymer Hinge” Myth

Because the originals are no longer manufactured, some suppliers stepped in with alternatives:

  • 3D printed plastic versions: Lightweight, usually promoted with great enthusiasm online, but rarely proven in the long term. As Ron dryly points out: “The originals were metal. Why replace them with plastic? That’s just pointless.”
  • Hand‑machined aluminium replacements: Beautifully made, but prohibitively expensive. Owners frequently report quotes of £100 or more per hinge – and with four hinges required per door, the total is extraordinary.

This inflated market is driven by the perception that Hymer hinges are “special” and cannot easily be replaced. But according to Ron, that simply isn’t true.

“It’s just a hinge. There’s zero reason to pay a hundred quid for it.”


The Common-Sense Fix: Ellbee Caravan Hinges

The closest near‑match for the originals is the humble Ellbee caravan door hinge. These are still readily available online and in caravan parts shops, typically costing under £40 for a full set of four.

What makes them so good?

  • They are almost identical in profile and function.
  • At most, they require minor modification (a little drilling or adjustment of screw spacing).
  • They’re made from metal, just like the Hymer originals.

Some owners report that no modification at all is necessary for a direct swap. Ron himself advises simply buying a spare set at today’s low price, given how cheaply they can be sourced compared to custom-made options.

“At £7 each it’s a no‑brainer,” he says.


Beyond Ellbee – Other Practical Options

While Ellbee hinges are the closest direct replacement, it’s worth noting that many Hymer owners have solved the problem simply by browsing hardware shops and picking from the thousands of different hinges available. As long as the replacement is sturdy enough and allows proper door alignment, there is no magic “Hymer‑only” specification.

One owner even recounts replacing his broken hinge with a simple steel one found in a Moroccan hardware shop. It wasn’t elegant, but it worked.


Preventative Maintenance: Don’t Let It Happen Again

The cheapest solution of all is to avoid hinge failure in the first place. Regular lubrication prevents seizing, which in turn prevents the stress that causes alloy to crack.

Hymer specialist Chris Womble stresses the importance of checking and maintaining hinges before they fail. His top maintenance tips are:

  • Check movement: If the door doesn’t swing freely when pushed, at least one hinge is binding.
  • Lubricate annually: Remove the hinge pin if possible, clean thoroughly, and lubricate with appropriate grease or penetrating oil.
  • If seized: Unhang the door and free the hinge with penetrating fluid. In stubborn cases, use a vice and hammer to work it loose – or even gentle heat with a blowtorch if all else fails.

Conclusion

The Hymer habitation door hinge problem has been overcomplicated for too long. While 3D‑printing enthusiasts and specialist machinists have pushed expensive or experimental solutions, the reality is simple:

  • A set of Ellbee caravan door hinges is almost identical to the originals.
  • They cost a fraction of custom parts and only require minor tweaks (if any).
  • Repairs can be possible for those with access to welding or DIY ingenuity.
  • Preventative lubrication and care will ensure many more years of reliable service.

As Ron – who has hands‑on experience and an engineering background – says plainly:

“Don’t pay silly money. Buy Ellbee hinges, modify if necessary, and get on with enjoying your van.”

 


PHOTO GALLERY - COLLECTED FROM VARIOUS SOURCES 

An original hinge - how is it attached? It has claws on the back!



The following photos are of an Ellbee conversion.












end of Ellbee photos

A hinge is a hinge! This unknown owner went his own way .... but it works.







A selection of hardware store steel hinges 


3D printed hinge - not enough info to recommend or criticise ...






Sunday, 3 August 2025

The Classic Hymer Electric Step

 The Classic Hymer Electric Step

The classic Hymer electric step is a powered platform located under the habitation door of the motorhome. It extends and retracts at the push of a button, making entry and exit easier. This article mainly concerns pre-1995 vans but also applies to a few post-1995 models.

Core Components

  • Step Motor and Cog Assembly:
    A 12V electric motor drives a toothed cog engaging a matching toothed quadrant, which moves the step smoothly in and out.

  • 12V Power:
    The motor receives its 12V power directly from the motorhome’s battery to operate the step. The warning light and buzzer circuit are powered by the battery but only when the ignition key is turned on. This prevents unnecessary battery drain when the vehicle is off.

  • Step Operation Switch:
    A Double Pole, Double Throw (DPDT) momentary switch controls the motor. The switch reverses the polarity of the 12V supply, so the motor spins in either direction—press one way to extend the step, the other to retract it.

  • Limit Switch:
    Located at the top of the mechanism opposite the motor, this “open to make” limit switch operates a warning light on the dash. +12V (with ignition on) connects to one side, ground on the other. When the step is fully extended, closing the switch completes the circuit, lighting the warning light. When retracted, the switch opens and the light goes out. The switch is similar or identical to common motorcycle brake light switches; part numbers like Hella 937171 and Durite 05791 have been suggested by owners as suitable replacements.

  • Warning Buzzer and/or Light:
    Alerts the driver if the vehicle is moved with the step extended. This differs by base model:

    • In Fiat-based Classic Hymers, the existing Fiat brake warning light serves this purpose. Fiat owners often get confused by this because if they drive away with the step left down, the brake light remains on, making them think they have a brake problem. Fortunately, after a few instances, most get used to this.

    • In Mercedes-based Classic Hymers, Hymer installed a separate, dedicated red warning light mounted on the dashboard or in the driver’s view. Unlike other Mercedes indicator lights, this light is unmarked with no symbols or text, illuminating only when the ignition is on and the step is extended.

    • Buzzer: Some vans have a buzzer that operates alongside the warning light. These are usually dealer or owner modifications and are not part of the original factory setup.

Troubleshooting

  • Switch Wear
    Switch failure is common after 20 or 30 years. Problems can be due to wear inside the switch or corrosion on the spade connectors. The switch is a standard rectangular DPDT (On)-Off-(On) momentary rocker switch (about 30mm x 22mm). For authentic replacements matching the original style, Marquardt (German-made) switches are recommended. Often, moving the spade connectors a few millimeters can clear corrosion and restore function.

  • Motor Failure
    The 12V motor can fail mechanically or electrically. Hymer used a standard motor common in electric window systems. Compatible parts known to work include:

    • Land Rover RTC 6640

    • Land Rover RTC 3821

    • Mercedes 0130821219

    • Mercedes 0130821016

    • Brose 187933-000

    These motors have an 8-tooth cog; others with more teeth won’t fit correctly. A common failure cause is dirty water ingress. Many owners successfully strip, clean, and reassemble their motors to restore function. A helpful YouTube video titled "Hymer step motor" demonstrates this.

  • Blown Fuses
    A blown fuse can cut power to the motor or warning system. The step motor is usually powered from the nearest habitation circuit. On pre-1995 models, this is often one of the top three fuses in the Hymer fuse panel. Later models with an EBL mark the step fuse as "Trittstufe" (German for step).

  • Quadrant Wear
    Teeth on the quadrant can wear over time, causing jerky or irregular step movement. New quadrants are available but costly. Some owners repair this by welding and filing new teeth.

  • Exposure to Elements
    Dirt, moisture, and grime cause corrosion and mechanical issues. Cleaning the step and wiring often restores operation.

  • Accidental Damage
    Driving with the step extended can cause it to hit obstacles, pushing it out of alignment. Classic Hymer steps are solid steel and can often be repaired by hammering or bending back into shape.

  • Manual Retraction
    If the motor or wiring fails, the step cannot retract electrically. To retract manually:

    1. Remove the three bolts securing the motor.

    2. Remove or secure the motor out of the way.

    3. Push the step back up by hand.

    4. Secure it with ties or straps.

    Some owners find manual operation acceptable and convert the step by removing the motor entirely, allowing the step to drop by gravity and be pushed back up by hand. To hold it securely in the up position, a slide bolt or turnbuckle (available in hardware stores) can be fitted.

  • Red Warning Light Flickers or Stays On When Step Is Up
    Usually caused by slight misalignment between the step and limit switch. Adjusting alignment typically fixes the issue.

  • Idiosyncratic Design: Random Intermittent Failure
    The step sometimes refuses to operate despite everything appearing functional, causing frustration. The best remedy is to tap or vibrate the step near the motor while pressing the switch. Many owners carry a rubber mallet for this trick.

Summary

The classic Hymer electric step is a simple, if occasionally quirky, system: a battery-powered motor drives teeth to extend or retract the step, and a limit switch triggers a warning light if the step is out while driving. Mercedes models have a distinctive unmarked red warning light, Fiat models share the brake light, sometimes causing confusion. Common issues include worn switches, waterlogged motors, and intermittent electrical quirks. Many owners swear by a well-timed tap (rubber mallet optional) to keep it working. With some care and experience, this trusty step keeps you rolling… or at least trying to!

PHOTOS - in no particular order.









step quadrant repair



limit switch location



manual conversion

merc warning light

step mounting bolts

this is how bad it can get


limit switch location