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split charger relay


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Welcome to the Out&AboutLive forums, Johnston.


I’m not sure what you are looking for as a “split relay charger” is not a term I’m familiar with.


There’s a 2018 model-year Autoquest handbook here




that has a wiring diagram and indicates that the electrical system is based on BCA equipment (that I’m unfamiliar with).


If you are looking for a “split charge relay”, nowadays that function tends to be integrated into a ‘black box’ that contains other electrical items that, historically, might have been fitted as separate components.This advert suggests that this might be the case with your motorhome




I THINK your motorhome may have a combined 230V/12V consumer unit (that might also include the battery charger) and, if that’s the case, it’s within that unit that I’d expect the relays to be.

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I think what your Elddis has is one of the BCA Distribution Box variants that Bailey has also used for their caravans. I’ve attached below a couple of Bailey-related images relating to the BCA boxes and the 2nd image shows what’s inside. Hopefully Elddis will be able to tell you if there’s a split-charge relay in the BCA box or if the relay is elsewhere.



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  • 3 weeks later...

Hi, I have had a reply from Elddis.


Hi Mr Dixon,


We have checked this and here is the update.

This is board mounted within the PDU.

When the vehicle alternator is working it provides power to the Fridge and charges the Leisure Battery all the relays are located within the PDU


(See attached file: Battery isolation.docx)


Kindest regards,


Customer Care

Erwin Hymer Group UK Ltd


I presume the PDU is the power distribution unit , which in my case is under the bed.

I have yet to investigate yet as suffering from frozen shoulder.


Battery isolation.docx


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The photo of the interior of the PDU which was previously provided by Derek, shows the footprint of six relays on the PCB. If I was looking for the split charge relay, I would first investigate the relay which has two 20A fuses adjacent.


From the handbook linked to by Derek, it seems that the lower (in picture) of these fuses is the habitation battery fuse. The location of this fuse is contrary to accepted good practice, which requires battery fuses to be adjacent to their respective batteries.


The coloured diagram provided to the OP, is obviously only explanatory and I hope that the depiction of three relay coils connected directly to D+, is not a representation of the actual connections. If two many relays are connected to D+, which can be connected directly to the alternator field, then the alternator may be reluctant to start charging. However given the manufacturing year of the OP's MH, it may well be provided with a converters panel, which provides an active low D+ signal and the previous sentence will not apply. (Active low means connected to earth (-ve) when active.) An active low signal would need different interface circuitry.



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It might be useful for Johnston to say why he needs information about where the split-charge relay is located in his Elddis Autoquest 155. Assuming that his motorhome has some sort of electrical problem, a detailed description of the fault might help forum diagnosis.


There is a variety of PCBs for BCA Power Distribution Units and a range of asking prices. It appears from online photos of the PCBs that the relays are all solder-connected, so replacement of a faulty relay and/or diagnostic testing may not be a simple DIY task, and - if a PCB were to be replaced - it would be essential that the correct part were purchased.


This ebay advert for a PCB for a BCA PDU




describes the item as


Brand new BCA Power Distribution Unit Printed Circuit Board (ONLY) fits the PDU Unit that I have put pictures off) that fits most Motorhomes / Campervans / Caravans or ideal for your new conversion. I have just paid £182.98 for it from PRIMA PARTS, it was ordered by mistake, we just had a bad earth. So grab a bargain at only £99.00


So before performing surgery on the PCB or buying a replacement, the first thing to do would be to ensure that basic trouble-shooting is carried out.

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Derek Uzzell - 2021-10-06 1:43 PM


It might be useful for Johnston to say why he needs information about where the split-charge relay is located in his Elddis Autoquest 155. Assuming that his motorhome has some sort of electrical problem, a detailed description of the fault might help forum diagnosis.




I assumed that he is wanting to fit a B2B, but I could have assumed incorrectly. If I was correct, there are other less destructive ways of installing a B2B than that described on the Motorhome Fun Forum, where one member admitted to destroying the relay with large pliers.


My favoured method is to install a separate fridge relay and fuse external to the distribution board, and to reroute the starter battery and fridge connections to this combination. The rerouting should be done in such a way, that the original connections may be easily restored.



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Thanks guys for all the info. I have a Van Bitz Battery Master to fit and the board looks like it may be messy to install extra wires to it or maybe able to tap into incoming cables, Or I can just run some extra wireing between Leisure battery and Engine battery. Will keep you updated when I get it finished.
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In Days of Old the fitting instructions VanBitz provided for their "Battery Master" (BM) product advised simple ‘3 wire’ connections to a motorhome’s starter battery, leisure battery and earth . This is the arrangement advised by Votronic for their similar “StandBy-Charger”




Nowadays VanBitz evidently suggests that a BM be connected via a motorhome’s split-charge relay






This is fine if the connections the BM requires are accessible, handily grouped together and the installer has sufficient electrical understanding.


This link describes connecting a BM to + and - points within a CBE Distribution Box




And this 2017 link describes fitting a BM to an Elddis Accordo 125.




The photos show that the Elddis has a BCA PDU - though a more complex version than the Autoquest Manual indicates - and the installer apparently made soldered connections to existing wires.


(My own Rapido motorhome has its starter-battery beneath the cab floor and its leisure-battery in the rear garage. Connecting a BM using the historic method would need a very long cable, making the split-charge relay recommendation much more attractive. Conversely, my previous two motorhomes had their starter and leisure battery close together and installing a BM using the historic method would have been a simple exercise.)

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