Ground Breaking Design in Charging/Inverter Integration?

We were brought a new Dethleffs recently which was a personal import into the UK only a few months ago that came out of the factory with a charging issue.

The Alternator charging problem wasn't discovered until the buyer was close to the Ferry terminal ready for the crossing back to the UK.

They decided to carry on and get Dethleffs to fix it in the UK under Warranty.

According to the new owner, the Dethleffs Dealer took one look and scratched their head in disbelief at the apparent complication of the Power Controller/Charging system.

After several hours and no progress the owner left as he arrived.

He then booked in with us, "Oh yes of course we can fix it, done hundreds of Schaudt equipped MH's, we often fix stuff even the Dealers can't", says I a little bit more confident than was wise.

When it arrived in North Wales I was completely stunned by what I saw. 

I was initially flabbergasted at the apparent silliness of it all, yet by the time we fixed it a few hours later I was in awe. 

It is, I think, a ground breaking direction, that while it initially looks overly complex, it actually breaks things out into separate entities. This should make changes simpler and more reliable. 

Fixes cheaper and quicker. 

The system looks complex because the traditional 'everything in one box' has changed to 'every independent function' to have it's own separate box, all connected to a proper Wiring Back Bone. 

Because each function is separate, it can be manufacturer independent. If you have an Alternator charge issue you just focus on that individual box.  

I now think it is a superb approach which we should all press to be fitted on all new Motorhomes..

In the case of this Dethleff the Schaudt Elektroblock was still there, an EBL 111, which we had advance information about as a new breed of Power Distribution unit that did not have the usual internal charger. 

Nor did it control Alternator charging or the Display Unit functions. 

The central element was a new and very advanced HSM 01 Board with a Victron Energy 1,600watt Inverter/Charger with built in 70 + amp mains charger 

Dethleffs are using tried and tested manufacturers but integrating them really well.

The quality of the installation was exceptional, well almost, apart from missing one little wire. Apparently the wiring loom has now been changed to correct the issue we saw.

In most Motorhomes, the Power Distribution unit is in the charger and Fuseboard, 'everything in one box', even the 230V distribution (which I think is poor practice) like the Sargent EC328. 

If you want to add any other devices, like another manufacturers Battery to Battery charger it is often difficult to hook into the existing system without extensive knowledge and some risk. The same applies to a high power Solar Solution or Inverter. Hence most 'add on's' side step the existing electronics, creating other issues.

What the new methodology does is create an open 'back bone' cabling board with high power cabling already in place. You can access it and link into it at almost any point. Any power you put into or take out of the system will then be reflected on the Motorhome control screen, as the Current Shunt is at the centre of the Back Bone and easily accessable.  

Everything else is then hooked into this Central power board, the elements of which can be almost any manufacturer. You could even replace 'modules' in isolation at a later date with other manufacturer items without impacting anything else.

For example, if you want to uprate the charger in 10 years time, just swap it. No dependencies on any other part as it is not proprietary. It allows you to install best of breed or lowest cost. Your choice. 

Also easy to decommission any entity, like an Inverter, at a later date if it failed and you felt you could live without it.

This not only makes fault finding easier, but resolution is simpler and most likely lower cost. 

The HSM 01 is effectively a high current Cable board, The label on the front states Hoch Strom Modul or rough English translation is 'High Current Module'

Huge 500amp rated cables from the Alternater/Starter battery comes in on one side. 400amp cables from/to the Habitation battery bank on the other side of the board. Cables so chunky you could start the engine using the habitation battery bank.

From this HSM 01 board, run the usual cables you would see supplying power to an Elektroblock, but this could be any power distribution system as that is all the EBL now does. It only acts as a Fuse board and power delivery mechanism.

The EBL no longer controls any charging either mains or Alternator.

The HSM01 provides the back bone for all charging. It does this by being able to take very heavy charging currents from the Alternator, Solar (up to 30amps) and Mains charging. See photo below.


For the first time in a Motorhome, it  puts in place the proper infrastructure for an Inverter and the big battery bank to support an Inverter.

Another plus is that installing any manufacturers B2B (Battery To Battery) charger is a piece of cake, all the infrastructure is there helping to ensure that the fitting is quicker (and therefore cheaper) because it guides the technician so reducing the risk of it being wrong. That should also ensure it is more reliable. 

The design may mean that a B2B is not often required anyway, see later section near the bottom of the page, as the charge voltage should be pretty much perfect, at least for Wet Acid batteries..

Bcause the cabling is so heavy duty, it is practical to have a Starter Battery assist mechanism using the habitation batteries if the Starter Battery goes flat.

One point discussed in depth recently is that of ECU controlled Alternators that try very hard NOT to charge the Starter battery to save fuel. Obviously not ideal for a Motorhome that will normally require the Alternator to work continuously. The HSM 01 has provision for an 'Alternator charge booster' that will raise the voltage from the Alternator to the 14.4v, or whatever is required, for the habitation batteries. This will ensure that the habitation batteries will always be charged at the optimum amount, even when the Alternator is operating in an energy saving low power mode. Once again, the Boost Charger can be from any manufacturer, it doesn't need to be Schaudt's own WA series units. 

From 2017, so we understand, a Buttner Alternator Voltage Booster might be an option for optimum Alternator charging of the Habitation battery. This will not only be a very effective B2B, but overcome any issues with Mercedes or Fiats future plans to adopt ECU controlled Alternators.     

Amazing integration with a Victron Charger/Inverter.

The 230v Mains charger could have been virtually any unit, but Dethleffs have adopted a powerful 70amp charger consolodated with a battery backed UPS/Inverter. So for the first time in a Motorhome, it will have the real ability to support a big battery bank.

If the mains input power is interrupted, the Victron sets an alarm and then seamlessly, without the TV even flickering, picks up the 230v mains load. 


What the Victron will also do is augment any additional 'mains input' if the Site EHU Bollard is not up to supplying the Full Monty.

For example if you were on a French 230v  '6amp max' Bollard but wanted to use an Microwave that had a start up current of 10amps for a second or two, the Victron would take from the habitation batteries the 'missing 4amps' for the few seconds it is required. All seamlessly.

Although it is a massively powerful charger, it has a long term 'Trickle'/Float charge/maintenance mode of just 13.2v if you want to stay on EHU 365 days a year. It additionally recognises that no power has been drawn for some days so every four weeks'ish gives a prolonged 14.4v 'boost' charge to ensure the batteries remain healthy.

The HSM 01 contains the shunt so all the Voltage/Current/charging info would go to a display which is the only item that needs to be compatible with the Schaudt HSM 01. 

We think that British Motorhome Builders should consider adopting this philosophy. Not just because UK Motorhomes seem to be heavily modified by the owners where this system makes that easier, but that reliability would be improved and long term cost of ownership lower. 

If Sargent could come up with an even better solution for the UK (maybe adopt International standards for the Display units?) it would give UK Motorhomes a competitive edge around the World to help our exports?.    

The heavy duty infrastructure in this approach ensures that voltage drop is zero, removing the need for many to install a B2B.

For the first time ever on any vehicle we saw exactly the same voltage at the Habitation batteries that we recorded at the Starter battery when the Alternator was charging, this despite the Habitation battery bank being located in the Garage at the very rear of the Mh.

Typically we see 14.4v at the Starter battery and 14.2v or less at the Habitation bank on Schaudt equipped vehicles.  Sometimes British built motorhomes can be charging the habitation battery more than one volt lower than the Starter battery because of voltage drop, 13.8v is typical. This can have a dramatic lengthening of habitation battery charge times when travelling. 

In this vehicle we recorded a rock steady 14.4v at both the Starter and the Hab batteries, even with the power draw of the Fridge/Freezer 'on Alternator'.

I was a bit disappointed to see the Alternator wasn't a 14.7v item to match the AGM batteries fitted by Dethleffs. The mains 230v Charger also seems to be optimised for non-AGM batteries, but when Varta/Bosch Powerframe batteries are just as just as good and half the price, does it matter?

Included below are the technical specs of both the Schaudt HSM 01 and the Victron Energy Multi compact Charger/Inverter.

Schaudt HSM 01.pdf Schaudt HSM 01.pdf
Size : 340.399 Kb
Type : pdf
Victron Energy MultiCompact.pdf Victron Energy MultiCompact.pdf
Size : 2206.29 Kb
Type : pdf