I finally got round to installing a spare Ctek MXS5 charger into the 2009 Familia 320 as the Scheiber unit doesn't charge the AGM battery properly and the technology within is a bit basic. The BIP is the Power Pack SE P/N 30.65100.84.

What you need - red and blue 6.3 mm spade terminals, ratchet crimping tool, screwdrivers, wire cutter and stripper, plenty of tea.

Firstly, and most importantly, disconnect any external mains power and also the battery terminals - you don't want any inadvertent shorting. This is the best way to get safe isolation.

Taking advice from Ray Lawrence's posts on this forum, I disconnected the transformer from the 230V input completely. So now the 12V circuits are powered from the battery even on EHU. The easy way to disconnect the transformer is to remove the live and neutral (brown and blue) spade terminals from the 230V busbars at the bottom of the unit under the main isolator. On my BIP, the neutral is coloured blue and the phase (live) is brown.

To access the BIP internals the cover has to be removed. This was a bit tricky as I have a water tank in the way. The easiest way to get access without removing the tank is to remove the four mounting screws to loosen the whole assembly then the BIP can be manhandled enough to get access to the cover screws (2 small screws). With a bit of joggling, the cover comes away. Once the transformer connections are disconnected from the busbar, I covered them individually with heatshrink tubing over the spade terminals to prevent any future shorts.As a further precaution, I cable-tie them away so they couldn't move too much. If you just cut the spade terminals off, you are left with an installation that can't be easily reverted to the original. As with most modifications, it's better to do things so it can be undone if necessary.

It is very difficult accessing the 230V busbar and making the connections and it becomes much easier if you remove the main isolator and the 12V BIP switch next to it from the DIN rail. The main switch is removed by pulling up the tag at the top with a screwdriver and the switch will lift away. Remove the live and neutral incoming wires first at the top, remembering to take a photo so you can put them back later in the correct phase.

The BIP switch is spring loaded at the bottom so just needs lifting off against the spring. The blue wire at the top of the BIP switch (12V supply from the vehicle = pin 9 on the trailer socket) needs to be removed before you can lift the switch off.

The Ctek smart charger comes with a 13A mains plug attached and various output lead attachments. Cut the mains plug off to about 50cm length of wire and strip enough of the 2 core (brown and blue) to install to the BIP main switch.. The Ctek is Class II so doesn't need an earth. Cutting the plug off will invalidate your 5 year Ctek warranty so if you are worried about this you could use a 13A plug adapter with a length of suitable flexible 2 core mains cable (250V rated), keeping the Ctek mains plug and wire intact.

The Ctek has internal short-circuit protection so you don't need any in-line fuse. It also has built-in temperature compensation for output voltage - you need this as it could get hot in the under-bed enclosure in hot weather.

I connected the Ctek 230V input at the bottom of the main isolator switch, keeping the colours correct so that the phase is not 180 degrees out. This means the 230V isolator disconnects everything (including the smart charger) when in the off position.

For the charger output, I used the 'Ctek Comfort Connector' with the M6 eyelets and cut the eyelets off, keeping the in-line adapter so that if anything happens to the Ctek unit and it needs to be changed, it's an easier swap.

There's no need to run a wire to the battery as there is already a connection in the BIP. The F5 fuse (15A) on the fuseway (connection number 12) is the supply to the battery with minimum resistance drop to the battery terminal. This is the charging connection of the original BIP electronics. This is fed from the BIP switch bottom end (red wire) so you can connect the positive output from the charger into this. Keep the existing red wire in place as this the feed to the 15A fuse on the fuseway.

You can see the two red wires, one to the fuseway and the other is the output from the Ctek.

Now you need to connect the battery negative side. It's not as simple as connecting to the 0V busbar as there may be several hundred milliohms of resistance to the battery negative terminal. The Ctek can deliver up to 5A of current so this could seriously affect the voltage applied to the battery. Usually a smart charger is connected directly to the battery terminals so that there is no voltage loss. Even at 1A, there might be as much as 1 volt loss (Ohms Law, V=I x R) if you connect to the 0V busbar (really this is an AC earth just for fault protection on the 230V circuits).

The battery negative terminal is connected by two wires (1) to the Schaudt Voltage Booster unit (on my Eriba it's a WS1214-8 model) 'Ausgang -ve', and (2) to the fuseway panel negative terminal busbar. There isn't space for a piggyback spade connector on the Booster unit so you will have to connect to the Fuseway point which is much easier anyway, You'll need to attach a 'piggy-back' spade connector crimped 6.3mm to the Ctek negative lead and the yellow-sleeved wire which is the connection to the battery See the picture.
When you have done that, all that remains is to make sure all the wires are neat and tidy. I cable tied the excess Ctek cabling behind the wheel arch behind the wardrobe. The Ctek itself sits on top of the plastic cable tray. I didn't screw it down as there are cables beneath but used velcro to attach - it's nicely wedged in there quite tidily..

Before you connect with an EHU, make sure the main switch is in the off position, connect the power and check the voltage across the incomer terminals. It should be 240V AC or thereabouts between phase (live) and neutral. Check also between neutral and earth - should be 0V AC. If your phase is correct then you're done. Switch on the main switch and the Ctek should power up. If you wait 2 minutes and the Ctek power light flashes, then your battery isn't connected correctly.

With the caravan on EHU and the Ctek correctly working, check the voltage directly on the battery terminals. You should see between 12.6V and 15V unless the Ctek is desulphating the battery (stage 1) where it will output 15.8V. If it's not in AGM mode then you should see 12.6V to 14.4V. My battery showed 14.9V at stage 4 charging (absorption phase). It is advisable to make sure the battery reaches stage 7 (Float) before leaving unattended for a long period - just in case the battery is faulty and the charger throws up errors.

Here's the completed unit without it's cover, with the Ctek charging in AGM mode, with the caravan connected to EHU.
I left the transformer in to allow the setup to be reverted to the original in future, if so desired. Nothing in this upgrade is irreversible.

The BIP switch (32A MCB) supplies the towing car power to charge the battery when connected. So leave this off (down) unless you are actually towing and want to charge the battery from the vehicle's alternator. If you leave the switch on when not towing, there won't be any impact except to have your battery voltage appear on pin 9 of your trailer plug. Very handy if you want 12V for testing your road lights at the trailer plug, or if you want to check your battery voltage from outside.

In all it took me about 2 hours with a couple of tea breaks. I think it's a very useful upgrade and I'm indebted to the other Eribafolk on here who have provided lots of advice.


Pete