Schaudt Elektroblock – DIY replacement

The Schaudt Elektroblock is an all-in-one power distribution, control and battery charging system for Motorhomes & Caravans – predominantly fitted to German built vehicles. Our’s recently started misbehaving on a recent trip to Europe, and while it was sent away and repaired by a specialist after the trip it made me lose some faith in the 20 year old components it is made from!

I started thinking about whether it would be possible to replace the whole unit with a plug-and-play DIY solution (our version – an EBL 4-105 – is not available anymore, and current versions (which wouldn’t be a direct swap anyway) are over Β£500….)

On reviewing the Schematics and poking about inside the unit it became clear that there is not actually all that much to them, most of the intelligence is in the battery charger bit and by separating out the functions I could use an off-the-shelf battery charger and create a separate power distribution system that plugs straight into our motorhomes wiring.

This is the inside of the unit – the large transformer and lower circuit board make up the battery charger, the upper circuit board is the power distribution, fuses, relays etc. The rest of it is fresh air!

The first step is to select a suitable battery charger that can be left permanently connected to the leisure battery – I selected this 11amp automatic unit from Absaar (similar capability to the 10amp unit in the original Elektroblock)

Note: I ended up not using this particular charger, as it makes an annoying loud buzzing noise when it is operating! – but it’s useful for showing the process I went through in integrating it to the motorhome

To prepare the mains side of the wiring I replaced the original 3 pin plug lead on the charger with a ‘kettle’ type socket. This allows the motorhome wiring to plug straight in.

This is the Elektroblock in it’s original location inside a cupboard on the right hand side of the cab, the metal angles on the bottom slot in channels in the wood.

Adding some 90 degree metal angles to the sides of the new charger allows it to slot into the exiting channels

Next step was to design a distribution and fusing system to handle the rest of the Elektroblock functions, based on the original schematics for the EBL 4-105. This is the schematic for the new system:-

The main functions are as follows:

  • Relay for split charge (to charge the leisure batteries when the engine is running)
  • Relay for the fridge (to power the fridge from 12V when the engine is running)
  • 12V systems relay (to turn the 12V supplies on when switched on from the control panel)
  • A shunt to measure the current going in/out of the leisure battery, to drive the ammeter on the control panel
  • Fuses to protect all the circuits
  • Plugs to connect to the original motorhome wiring (1x input mate-n-lok, 2x output mate-n-lok, 1x solar connection mate-n-lok, 1x 8-way panel connector)
  • Connection points for the 12V feed from the charger
  • Flyback diodes for the relays, and a diode to prevent the leisure batteries from back-feeding the alternator

This is the control panel as fitted to the motorhome that interfaces to the Elektroblock. It contains a voltmeter for starter and leisure batteries, an ammeter for current in/out of the leisure batteries, and a switch to turn the 12V circuits on/off

The two relays for the split-charge and fridge are switched from theT alternator D+ terminal, so I used standard automotive 40A relays. To house these I picked up a combined relay/fuse box that holds 2x relay and 8x automotive fuses, and comes complete with all the necessary terminals to wire it up:-

Fuse and relay box, cost just Β£7.59 delivered

The relay for the switched 12V circuits needs to toggle between on & off when it receives a momentary signal from the control panel, so a more specialised relay is required here. I used a Finder DPST DIN rail mount 12V latching relay. This has the added benefit that it can be actuated manually, so should the control panel/switch/wiring fail, the 12V circuits can still be switched on/off by pressing the button on the front of the relay:-

Finder 12V DIN rail mount relay

For easy access I opted to mount all the distibution components to a wooden board that will go above the charger unit in the cupboard. The fuse box and shunt are screwed directly to this board, and a din rail is added to hold the Finder relay and some DIN rail mount distribution blocks for the various circuits. Here is the fusebox, finder relay and shunt mounted up and the first bits of wiring connected:-

Here is the board with all the wiring added, ready for the plugs to be terminated:-

The flyback diodes for the relays in the fusebox are connected directly to the coil terminals – you can see them here in the fusebox wiring:-

The flyback diode for the finder relay is connected to the coil terminals (top and bottom of the relay) and lay down the left side of the relay itself

Next job was to start terminating the plugs. For the panel connector I could only find the mating half in a PCB mount version, so I soldered it onto a piece of prototyping board and added an 8-way PCB mount screw terminal connector to wire it up:-

In the original motorhome wiring the starter battery sense line and the two shunt sense lines are directly connected to batteries and fused at 30A – too high for the wiring to the panel. To protect these circuits I added inline fuses holders to the wiring to the panel connector with 800mA glass fuses:-

Next job was to add all the pins and sockets for four main Mate-n-lok connectors:-

This is it all terminated and ready to go:-

Here is a top view of the fuse & relay box with the lid removed, showing the fuses and relays in place:-

Here is the new system connected to the wiring in the motorhome and ready for final installation

And the final installation inside the original Elektroblock cupboard:-

The new system works perfectly, with the added bonus that the solar regulator can now charge both the starter and habitation batteries.

In case you want to create something similar yourself, here is a bill of materials – total cost Β£105.66 (note – the piece of wood and a few small lengths of different colour wire are from stock I had lying around, so aren’t included in the BoM, I also haven’t included the charger in the BoM as you can pretty much use any charger you like as long as it is designed to be permanently connected to a battery – I ended up using a CTEK unit)

I’m pleased with the outcome and it’s a saving of many hundreds of pounds over a new Elektroblock! Let me know what you think – is it a good idea?, have I missed anything? Also, let me know if you want a copy of the schematic – I’m happy to share it.

Thanks for reading!

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19 Comments

  1. Great article! I am going to do my second VW Transporter DIY conversion and I am looking for inspiration how to do simple “elektroblock”.

  2. Classic example of superb DIY reverse engineering! EBLs, which came into use around 95 in Hymer and other motorhomes, while being of decent quality, also introduced a single point of failure, compared with the earlier systems which used separate components. I have seen many an online post detailing the angst caused by a faulty EBL.

    For those who don’t fancy a job like this, EBLs can be repaired quite quickly in the UK by two specialist companies – Apuljack Engineering, and A & N Caravan services – both on google and I am not connected to either, just an enthusiastic van owner.

  3. Hi

    Many thanks for this article, I’m planning something similar so it’s been very useful. I have a couple of quick questions if you don’t mind?

    1. What sort of diode did you use between the D+ in and the split charge and fridge relays?

    2. Do you have any more details about the connector for the panel? I’ve had a look around but can’t seem to find a suitable one, do you have a link to the one on RS by any chance?

    3. With the shunt fitted as it is, does it show on the ammeter on the panel how much the battery is charging and discharging?

    Thank you again for the article

    Tom

    • Dan

      February 24, 2020 at 5:17 pm

      Hi Tom!
      1) Diodes are all 1N4001 – it’s a common diode made by lots of different manufacturers, easily available from eBay, RS components etc.
      2) The panel connector I used is RS part number 737-8587, you should be able to find it here:- linky
      3) The shunt is fitted in the same way as it is in the original Elektroblock, so the ammeter in the panel reads correctly for both charging and discharging. You just need to make sure you select a shunt that has the correct mv/A rating – a shunt of the wrong spec will cause it to read either high or low.

      Hope this helps!, let us know how you get on and if you have any more questions just ask πŸ™‚
      Cheers, Dan

      • Hi Dan

        Thanks for teh speedy reply πŸ‘. I have got a few more questions if you don’t mind?

        1. How did you wire the diode into the D+ wire?

        2. Do you know what mv/A rating is needed for the shunt?

        I’m just trying to finalise the parts I need then hopefully can get it all wired up next week.

        Thanks, Tom

        • Dan

          February 26, 2020 at 8:52 pm

          Hi Tom – no worries πŸ™‚
          1) The D+ diode was just soldered in-line with the wire, with heatshrink over it to protect/insulate it
          2) I ended up experimenting to find the right shunt rating, but unfortunately I can’t remember exactly which one I ended up using! They were all 75mV FL-2 shunts bought for a couple of pounds each off e-bay, but in different ranges. I think I ended up with either a 40A (so 1.875mV/A) or a 50A (so 1.5mV/A) shunt.
          Good luck with the project! πŸ™‚ Cheers, Dan

  4. Hi Dan
    Inspiring article, especially now that i am looking for a solution for the problem i currently have. An annoying buzzing sound in the trafo of the Schaudt.
    What kind of CTEK did you use in the end and would it be possible to leave the schaud in tact only replacing the internal charger with an external one?
    The unit is almost simular to yours it is a ebl4-106

    Rgrds Patrick

    • Dan

      March 24, 2020 at 4:09 pm

      Hi Patrick – thanks for the comment. I used a CTEK MXS-10. It should be easy enough to leave the elektroblock intact and just bypass the internal charger, just look for where the low voltage side of the internal charger connects to the circuit board and connect the CTEK into this point instead. Hope this helps, let us know how you get on! Cheers, Dan

  5. Hi Dan I bought a motor home with EBL 4-105 missing your EBL 4-105 replacement look great and would solve a big problem for me but I do not have a electric no how to take that on is there anybody you no would Biuld me a replacement like one in this article thank from a very stuck ken allen

    • Dan

      February 28, 2021 at 5:43 pm

      Hi Ken – thanks for the comment! I’m afraid I don’t know anyone who would build this from plan for you – do you have a technical college or similar near to you?, if you can find one that does electronics or auto electrical courses there are likely to be students there willing to do something like this in their spare time for a few beer tokens!
      Otherwise it’s probably worth giving someone like Apuljack engineering a call – they may have a repaired second hand unit kicking about for a good price. Cheers, Dan

  6. Hello, came across this article and have read it with interest. Although no problems with my 4-105 yet, I do have an issue with the now antiquated (1998) charger. Also I have replaced the leisure batteries with AGM batteries and have read they need a different charging voltage or manner of charging. The charger in your article would achieve this, but the charge coming from the alternator would not get close.(75pc). Thus a battery to battery charger might be a better alternative, but can this be connected to the existing split charging relay or?? I would be interested in your suggestion, thanks Rudy

    • Dan

      May 12, 2021 at 9:04 pm

      Hi Rudy – it’s worth checking your Elektroblock as they often have a small switch to select between flooded and gel-type batteries (the switch alters the charging regime as you mention). If you are finding the standard split-charge system is not performing for you then you could install a battery to battery charger, I see no reason why you couldn’t connect it to the output of an existing split charge relay (do you have a separate split-charge relay, as opposed to the one inside the elektroblock?) – however I suspect a lot of people talk themselves into needing/wanting a battery to battery charger, rather then actually needing one! Cheers, Dan

      • Rudy van der Goot

        May 19, 2021 at 12:42 pm

        Hello Dan, thanks for you quick replay, as said my EBL is a 4-105 and does not have a switch, so will replace the original charges with the one you suggested as that one is clever enough to charge anything currently on the marker (GEL, AGM etc), I have read that staying with the current setup will shorten battery life as the charge can only go up to 14.4 volt whereas the currently installed batteries really require 14.8 volt and I believe a different charging curve.
        This bypass is thanks to you description not too drastic, but problem remains that whilst driving the leisure batteries will never get to 100% (hence my battery to battery question).
        One more question if I may, what made you change all the individual gubbings as opposed to leaving the basics of the EBL as they were?

        Thanks

        • Dan

          May 19, 2021 at 9:52 pm

          Hi Rudy – as it wasn’t clear where the fault with my Elektroblock was it was easier to replace the whole thing than to try and replace just certain buts of it – it was a fun project anyway πŸ™‚

  7. Hi Dan.
    OThank you for publishing your article – but oooohhh, how I wish I’d seen it a year ago!!
    I discovered a big problem with my Schaudt EBL 264, centred around the fridge 12 volt control systems having been shorted out in former ownership and a none too professional job made of getting round it. In effect I rebuilt an external ‘mimic’ of the 12 volt control system (with a good deal of wonderful help and advice from ‘elsewhere’) but it was a lot less than straightforward, especially in view of the very low D+ output available from the alternator.
    Either way, your route of completely replacing the EBL would probably have been less work!
    Since I’m still less than convinced of the reliability of the rest of the EBL internals – evidence of burnt and bridged PCB tracks – I would be very grateful for a copy of your schematic. If time allows, I’ll probably do the same as you, just for the added confidence in the system.
    A question – or two:
    1. My Schaudt control panel, whilst different, is in essence the same principle. Is there a way of measuring the existing EBL shunt to replicate it without too much experimentation?
    2. Some of the original mate’n’lock connectors were destroyed when the system was damaged. I replaced the necessary but was never too enamoured with the size and robustness of them, especially considering the current the might be required to carry. I know it would mean re-terminating quite a lot of cables but would you see any merit in replacing them with something like properly crimped ring terminals on a screw/bolt post terminal block?
    Will

    • Dan

      August 24, 2021 at 9:37 pm

      Hi Will – thanks for getting in touch! I will send you a copy of the schematic to your e-mail address :). You could measure the existing shunt by using a constant-current power supply to put say 10A through the shunt then measure the output in mV (or use a constant voltage power supply and a known load (such as a power resitor) to give you a known current, then measure the output as before). The mV output should be linear and zero-crossing with respect to current, but you could always measure at a few different current levels for completeness. Replacing the mate’n’lock connectors with ring terminals would be robust but is likely to be very bulky? You could always re-terminate with a ‘better’ connector family if you wanted – Deutsch connectors have a good reputation and are readily available. Let us know how you get on! Hope this helps, cheers, Dan

  8. Hi Dan ,

    Great article ! Would it be possible to send a copy of the schematic please ?

    Thanks
    Dan

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