Motorhome conversion

Table of contents

Reading time 6 minutes

Updated – November 1, 2023

warning: When converting a motorhome, “just” isn’t enough in any of the following conversion measures! You should plan at least twice or three times the time that you would initially estimate. Adversity arises regularly with Murphy's reliability...

If you're planning a longer trip in a motorhome, unless you have two left hands - fortunately 😉 - you won't be able to avoid modifying one thing or another...

In most cases, the conversion work is not just limited to a few manageable actions. One entails the other. And if you do, then you can - just -, well, actually - just as well... - convert almost anything. To the chagrin of the woman, who just claps her hands over her head and rolls her eyes.

We purchased a Flair 7100 used. If we had bought it as a new vehicle... well: you might think that if you buy from a well-known manufacturer, then both the documentation and the execution should be completely and properly.
Over 600 pages of manual, after all! Yes, far from it. It starts with references to “site maps” of various areas, whether electrical, water, etc., which are neither in the manual nor available upon request from the manufacturer.

Unfortunately, there is a lot from crooked substructure strips, more or less chaotically laid water pipes, which, thanks to the lack of a site plan, you neither know where they come from nor where they go and whether they carry hot or cold water, as well as poor quality of installed shower facilities. which - given the six-figure purchase price - one would expect to find a higher quality workmanship.

Even without being a carpenter, electrician or plumber yourself, you quickly think: I can do that better. And this is where the disaster takes its course: you start here and there in order to get from there to there and ultimately open up a number of construction sites, far more than initially intended.

The more experience you have, the more you notice things that need improvement, for example the heating circulation pump, which tends to rattle because the 20 cm long axis of the “whisker” in the water bath is not really central and certainly not runs balanced.

Of course, for the sake of fairness, conversions based on individual use are not included here.

The following articles on this topic are currently available:

First orientation – find cable routes

Remove all floor hatches, not forgetting the ones in the cupboards! If you want to pull new cables, you have relatively good options here. You should use a guide wire such as a 1.5 mm2 installation cable that is about 2 m long in order to juggle flexible cables specifically through the floor labyrinth. It's best to lay several cables or at least multi-core lines at the same time so that you have reserves later if necessary.

Tense aspects – part 1

For additional DC supply lines, for example 12-way fuse holder Indispensable for standard vehicle fuses. The existing fuse boxes are already well utilized. The
The overview becomes better if you use separate fuse holders.

When choosing cable cross-sections, more is definitely better, although more expensive. But risking an unintentional “electric floor heating” or even a cable fire later because of false modesty is certainly not desirable. So at least choose the supplying battery cables with large cross-sections. The outgoing lines correspond to the ampere rating of the fuses to be used, or the required power requirement of the consumer(s) to be connected.

The necessary cross-section of copper cables for DC applications can be calculated here, as can the voltage drop. The yellow fields are editable:


cross-section	17.2414	sq. mm	voltage drop	0.1979	v
length	10	m	cross-section	17.42	sq. mm
Electricity	10	A	length	10	m
permissible voltage drop	0.2	v	Electricity	10	A
Conductivity CU	58	SI/m	Conductivity CU	58	SI/m

Conversion – LED instead of halogen

Converting energy-guzzling halogen lights as interior lighting to LED strips also brings with it some surprises.

It's not just illogical switch assignments that cause problems. For example, the switch for the two spotlights in the passage to the shower and toilet is located in the aluminum cover between the kitchenette and the sofa (in the bar version). Or the switch for the step lighting located in the control panel at the head of the loft bed in front of the bed (instead of attaching it to the side near the step where it is needed).
Even randomly placed, free-flying fuse holders on boards, in cupboards, etc. can cause problems, as they are not documented anywhere in the manual. The crowning achievement are the formulations on page 251 in the over 700-page flair manual:

FlairDt_version8_04.pdf

“Due to the large number of different Flair models, the location on the three light fuses cannot be named in detail.”

The security odyssey

The “relay box” that houses various fuses is referred to for the first time on page 38. However, you can only find out what the relay box is and what it looks like on page 251 thanks to a photo. The manual is completely silent about the location (namely in the outer flap on the right below the sofa).

The reason for the search was the activation of the fuse, which is apparently responsible for the lighting in the shower, loft bed, kitchen and sofa area. However, all of the plug-in fuses in the relay box were intact. Where this security is hidden remained in the dark in the truest sense of the word.

The cause of the fuse mishap was the reverse coding of the connectors installed with the lights in the right bunk bed area: previously black was negative and blue was positive. But here blue was minus and brown (instead of black) was plus. In themselves, coded connectors are a great thing, as they protect against exactly this kind of trouble. To save Niessmann & Bischoff's honor, it must be said that Hymer supplies the cable harnesses. Nevertheless, documentation responsibility lies with Niessmann & Bischoff.

Preventive measure

In order to be protected from such imponderables in the future, all newly installed consumers have specially laid cables and a cable that is accessible from the inside at all times Fuse box secured. Defective fuses are indicated by an LED located directly next to the socket. This eliminates the need for searching and measuring. It should not go unmentioned that documentation should be written for such laid cables and assignment of fuses, including strength. On the one hand, in a few years you will hardly remember which fuse is assigned to which consumer, nor would you want to subject a future buyer of the motorhome to the same unpleasant experiences.

Cosmetics

In the course of converting from halogen to LED strips, we had to cover up the unsightly holes in the removed halogen lamps and also somehow get rid of the speaker cutouts in the aluminum profiles below the tall cabinets.

After we had good experiences with acrylic glass in the shower, the decision was quickly made: measure the acrylic glass panels and cut them to size Nordic panels Order online in Stade and pick it up after completion to save freight costs.

Provided you measure carefully, the panels fit like a glove. The curve of the lower wall cupboard ring only needs to be carefully reworked at the ends on the driver's cab side.

The plates were manufactured with a depth of minus 10 mm in order to be able to mount the 10 mm wide aluminum corner profiles of the LED strips in front of them at a distance of a good millimeter from the back of the wreath.

The challenge was the cable entry into the interior of the cabinet and the laying, which was mainly carried out in the upper slat area with the standard ambient lighting.

Tense matters

In order to meet the different needs of various devices, DC/DC converters are provided. Each consumer is protected separately so that the functionality of several consumers is not lost in the worst case scenario.

Incoming and outgoing cables are organized in cable ducts.

LED strips attached to the sides ensure a bright working environment on both sides. This installation is carried out on the driver side. There is also a double charger for Makita batteries behind the driver's seat. Since this cannot be operated with direct voltage, but only with 230V alternating voltage, a separate DC/AC inverter was installed for this purpose.

All chargers for batteries, devices with built-in batteries, etc. are located on the passenger side. The Makita cordless vacuum cleaner also found its place here, between the table (gas box panel) and the passenger side panel, below the charger installation.

After a number of power consumers, operated with low voltage such as mains voltage, have accumulated over time and several sine wave inverters and their respective mains priority circuits have found their place, sufficient storage capacity should now be ensured.

For this purpose, four 12 V LiFePo4 batteries with 280 Ah each (max. current draw 240 A each), so a total of 1,120 Ah (or 960 A), are connected in parallel. In order to transmit the maximum current possible for the installed 4 (8) kW sine wave inverter largely without loss, two 400 square Cu busbars (max. continuous current load 715 A) are mounted on insulators directly above the batteries. These are the 50 square (approx. 200 .. 240 A at 10 .. 30 °C ambient temperature) cable routes from the battery to the balancer and battery management system (BMS with Bluetooth add-on), as well as the connection to the 4 (8) kW Sine wave inverter, mounted directly next to it, extremely short and therefore low-loss.

All related components, with the exception of the 4 (8) kW sine wave inverter, are from Victron, including MPPT controllers for the 800 W PV modules and charging boosters. Power management runs via Victron Cerbo GX, including Bluetooth add-ons for non-smart products.

All producer and consumer statistics can be accessed and balanced accordingly. This means you are protected from unpleasant surprises, provided you look at this data at regular intervals.

Why so much effort?

In order to be able to work online if necessary, a Mac Mini M1, a duplex scanner, as well as a duplex LASER printer, including a Bluetooth keyboard and trackpad and a 15.6″ monitor, along with three others, were used for the PTZ -Exterior cameras installed on the left, right and rear (with audio). Mac Mini and LASER printers require 230V, the scanner works with 24 V DC, the monitors use a 230 V power supply (unfortunately, operating them with 5V was not possible due to mutual interference). When driving, the vehicle is recharged via the charging booster. When stopped, only the Mac Mini and a monitor are running if necessary.

This way, there should be plenty of energy available, at least in summer. In winter or on cloudy rainy days, the gas/petrol hybrid generator with its 3.3 / 3.9 kW (gas / gasoline).