Technical Campervan wiring

[Stevelightning]

Hi all a complete newbie here and hoping to get some help. I am doing a self build camper and looking to wire up my sargents kit to the cab so as I start the engine it disables the back of my van. Does any of you helpful people know the best way to do this as I am not really familiar with cab wiring. I am capable of wiring the system up but I just need to know what feeds I need from fiat. The van is a 2021 ducato.

Thank you for any help it is truly appreciated.

 

[Communicator]

Hi Steve,
Welcome to the forum.

Does your van have a converters panel at the bas of the RHS "B" pillar? An active low (connects to earth when engine running), D+signal is available at pin 2. See attached extract from x250 Training Manual.

If no converters panel (basic van), then more of a problem but you could cosider a voltage controlled relay module from Ebay supplied from a suitable ignition switched supply.

If you have yet to purchase a Sargent outfit, then perhaps reconsider and use a CBE system instead. The CBE distribution boards take an ignition switched supply and uses it in a similar fashion to that described above. The controlled output (simulated D+) is made available for other purposes.

Also do you really need to disable the habitation electrics? It does not happen on my own commercially converted PVC. See this thread on Motorhome Matters forum, and scroll down to the post by Derek Uzzell.

 

[Stevelightning]

Hi thanks for your reply. I have a sargents kit fitted. Everything is running fine from the leisure battery but I am wondering how I wire it up to the cab side so the sargents kit charges the leisure battery when the engine is running.

It is the basic model so there is nothing at the b post next to drivers seat.

Thanks for your help.

 

[Communicator]

Hi thanks for your reply. I have a sargents kit fitted. Everything is running fine from the leisure battery but I am wondering how I wire it up to the cab side so the sargents kit charges the leisure battery when the engine is running.

It is the basic model so there is nothing at the b post next to drivers seat.

Thanks for your help.

For the main connection to the starter battery you could consider using the "body-builders fuse". See fuse 3 on attached extract. You may need to fit a suitably rated "midi fuse".
If your van has a smart alternator, then a B2B will be required. I have attached a Sargent diagram which may help.

As I mentioned earlier obtaining a valid D+ signal could be more complicated, when there is no provision at the B pillar.

 

[HughJampton]

If the vehicle has a smart alternator, and a DC-DC (B2B) is required, then it might be sensible to consider units such as the Victron ones (I suspect there will be others similar) which have built-in voltage-sensing logic which avoids the need for a D+ connection.

The (switching) voltage values are set for a "default" smart alternator, but are configurable. I'll be honest and admit that I'm personally not sure how well the values match the Ducato configuration, but I think there are a good few such installations around.

 

[Stevelightning]

Ok thank you. I have a mate now helping. He is a auto electrician so hopefully he can guide me in the right direction. Thanks again for any help.

Does the van need the D+ signal to run the charger in the sargents unit ec155 or is this just fed from the vehicle battery. Could I just not bother with D+ and isolate ithe van at the control panel? Is this an easier option?

Thanks again

 

[HughJampton]

The charger in the Sargent unit is 230v to 12v (i.e. mains only). A D+ signal isn't needed on hook-up for this to function. (The D+ input controls the EMC relay switching capability, which (IMO) is not critical, and discussed elsewhere).

"On the road" charging is generally provided via "split-charge" relay (or in the case of a "Smart Alternator" a B2B unit), and AFAICS such provision is not made in the EC155. (My interpretation of the EC155 wiring and user instructions is that the split-charge and fridge relays on a motorhome/campervan should be separately provided outside the EC155 provision, with the relay feeding the EC155 D+).

As per previous posts, alternator charging can be provided via a voltage-sensing relay, or, in the case of a smart alternator via a voltage-sensing B2B.

(If you're fitting a 'fridge, there'll be some questions about that as well )

 

[Stevelightning]

Thanks again for your replies. The back end of the van is wired up and working off the leisure battery. I have a 12v compressor fridge wired directly to the leisure battery and have installed a switch for if I ever need to turn it off and also a inline fuse. Will a split charge system affect any of this if I run one in. I may not bother with the D+ in the end then.

From what I understand is that the cab doesn't actually need connecting to the sargents unit then as it isn't actually doing anything. The mains hook up and solar panel are the charge supply to my leisure battery. Then everything powers off that. Am I right?

Then a additional split charge system can be added at a later date.

 

[HughJampton]

As I interpret it, that should work, though I personally wouldn't want to do without charging from the engine (viability depends very much on power demand and camping practice - offgrid vs EHU).

 

[Communicator]

The basic split charge arrangement is simply a relay (electrically operated switch) which is operated when the engine is running, and connects the two batteries together for charging. The D+ signal is used to operate the relay. If a B2B is installed this split charge system has to be disabled, otherwise the split charge relay becomes a short circuit between the input (vehicle), and output (habitation) batteries. So for battery charging you should not need the D+ signal, if a suitable B2B is installed.

However as @HughJampton has pointed out a 3 way, or automatic fridge will require a D+ signal, so that it only draws power from the 12V system when the engine is running. Some installations connect the fridge 12V element to the habitation battery, but still control it via the D+ signal. This means that the fridge is supplied via the split charge relay, or the B2B as applicable. This reduces the capability of either system to recharge the habitation battery.

Explanation. I use of the term "habitation battery" instead of the frequently used misnomer "leisure battery". A leisure battery is a type of battery that was and still is frequently used in the habitation role. Strictly, a leisure battery is a lead acid battery designed to withstand many deep discharges at relatively low currents, unlike a starter battery that is required to deliver a large current for a only a short time when starting the engine. My habitation batteries are dual purpose batteries and can perform both functions, but they could be lithium batteries, which again are not leisure batteries. Unfortunately Sargent who I believe evolved from the caravan industry still use the term "leisure battery". You will not find it used on continental MH systems such as Schaudt, or CBE.

 

[HughJampton]

The OP has said he has a compressor fridge wired to the "leisure" ( ) battery, and if it's a 12v only, probably won't need a D+ to control that. It does cause a potential issue without any alternator-based charging to the battery, however. A long journey (presumably with the fridge in-use) without noticeable input from any solar charging (quite common in UK-type weather) will hammer the battery somewhat. Follow this by a stretch off-grid, and issues may arise with battery capacity.

 

[Stevelightning]

So this particular sargents kit needs a independent split charge to charge the battery while engine is running? I assumed the built in charger ran off 12v too and not just 230v. Thanks

 

[HughJampton]

As Communicator's post above, charging from the alternator is conventionally achieved via a split-charge relay (or in the case of newer smart alternator installations a DC-DC (B2B) charger.

Sometimes the PSU/distribution units have a (the) split-charge relay built in (most Schaudt units for instance), but in the case of the EC155 I don't think that is so, and alternator charging provision (and also where required, provision for three-way fridge supply) needs to be made separately and externally.

I can find no reference to alternator charging in the EC155 instructions, and the (motorhome) wiring diagram implies it is separate and external (implied from the fact that the fridge relay is also shown as external)..

 

[Communicator]

e OP has said he Thhas a compressor fridge wired to the "leisure" ( ) battery, and if it's a 12v only, probably won't need a D+ to control that. It does cause a potential issue without any alternator-based charging to the battery, however. A long journey (presumably with the fridge in-use) without noticeable input from any solar charging (quite common in UK-type weather) will hammer the battery somewhat. Follow this by a stretch off-grid, and issues may arise with battery capacity.

Thanks Hugh, I obviously missed that part.