Carthago Split Charging Unit

[G7UXG]

I'm exploring the possibility of putting a B2B charger on my Carthago, but I understand that I'll need to disable the existing split charging unit. Does anybody know where it is? Is it a separate unit, or is it built into the electronic gubbins in the boot? I can't even identify a fuse for it. Is it likely to be an ordinary automotive fuse, or one of the midi fuses which are attached to the multi-connector that is on the +ve of the vehicle battery?

It's a Carthago 5.5XL but I think the electrics are the same on all the 'A' classes. Electronics are CBE

Might even consider a Votronic triple unit (mains/B2B/solar), although they're a bit expensive.

Thanks in advance.

 

[TinaLes]

I have no Idea where ours is either, and I will need to locate it when I also fit a B2B.
Only suggestion I can offer is do as my dealer said, go on the Carthago website, click on customer services, then click on technical, then type in the question to the technical team listing of course your model and year of manufacture.
They were very good last time I asked something, they responded in 48 hours (weekdays) although being German their answers are very short and succinct if you get my drift
Good luck
LES

 

[SteveandSue]

We have a 2013 - coachbuilt - uses CBE
There is a 50 amp fuse at the battery that comes from the charging unit. Not in the van now - but - think there are 2 red 50 amp fuses and a brown ?? amp - bolt down solid type fuses -
we have just had an issue with engine battery charging on ehu so I know for us it is the middle fuse red one - second from front of van that disconnects charging unit - put new fuse in and now works fine again. ( yours should be easily identifies with a meter if you connect/disconnect ehu?) - As an aside - I have also put a small digital volt meter direct from battery - this gives a permanent and accurate reading visible- to avoid problem again (long story)
Sure someone with more technical knowledge of your van will be along soon

 

[G7UXG]

We have a 2013 - coachbuilt - uses CBE
There is a 50 amp fuse at the battery that comes from the charging unit. Not in the van now - but - think there are 2 red 50 amp fuses and a brown ?? amp - bolt down solid type fuses

Thanks, thought it might be one of those but haven't tried them yet.

 

[TinaLes]

When you do find the split charge relay, then thats the ideal place to fit a Battery Master also, keeps the cab battery maintained when stood idle.
LES

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[SteveandSue]

Yep = thats it - good photo. (least my memory is OK) so ours was the red fuse which would be in the middle -but yours may be different -Know nothing about split charge relays!
Digital voltage meter was best £7 spent in a while - can see exactly whats going on now

 

[Robert Clark]

I think that removing the fuse will also turn off the D+ signal to the fridge

 

[Pausim]

The relay is built into the CBE distribution unit. The CBE manual says there is a resistor that can be snipped from the circuit board but that sounded too permanent for my liking. I installed a normally closed 70/100A relay on the B1 engine battery connection at the CBE distribution unit. The relay is triggered and opens when the B2B turns on (D+). In this way the engine battery is left connected to this system as normal until the B2B powers up and then disconnects to prevent creating a loop. In effect it cancels out the effect of the CBE battery separator relay closing without losing any normal functions or doing anything serious to the CBE circuitry. My B2B is wired directly to the leisure battery which avoids pushing a heavy current through the CBE. I have an extra fused feed from the engine battery to the B2B.

 

[TinaLes]

Any chance of a picture, sounds like the perfect solution.
I will have to check out the wiring diagram for The CBE Dist board and try and see where the D+ feed is also.
Thanks
LES

 

[Poutie57]

Don’t know if this helps but I’ve installed a sterling B2b followed the instructions from sterling wiring it directly from the chassis battery, but following advice from other people I haven’t touched a single thing on the cbe side of things and although mine is a 2016 Laika Kreos it’s the same system as Carthago and it works perfectly well. I have done over a 150 days this year without ehu with no issues so I’ve used the theory of if “it works leave we’ll alone”

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[Pausim]

Any chance of a picture, sounds like the perfect solution.
I will have to check out the wiring diagram for The CBE Dist board and try and see where the D+ feed is also.
Thanks
LES

My motorhome is in storage but I will try and get a picture later in the week. This is the relay I used, together with the associated bulkhead socket. I also used an inline fuse (that I already had) so that I could bolt the existing wire onto it without cutting the ring terminal off. The fuse then feeds the socket and relay.

0-728-72 Durite 12V 80A-100A Mini Extra HD Changeover Relay

Durite 0-728-72, 12 Volts heavy-duty changeover relay at Arc Components Ltd. Automotive 12VDC 80-100A switch relay with 3 x 9.5mm and 2 x 6.3mm brass terminals.

www.arc-components.com

Don’t know if this helps but I’ve installed a sterling B2b followed the instructions from sterling wiring it directly from the chassis battery, but following advice from other people I haven’t touched a single thing on the cbe side of things and although mine is a 2016 Laika Kreos it’s the same system as Carthago and it works perfectly well. I have done over a 150 days this year without ehu with no issues so I’ve used the theory of if “it works leave we’ll alone”

With the Carthago wiring if the B2B is wired to the leisure battery then as the CBE battery parallel relay closes the the two batteries are linked which creates a loop. The B2B is then feeding both batteries and itself. This might go unnoticed but it means the B2B can not monitor the leisure battery properly. Also if the leisure and engine batteries are of different types then one of them will be getting the wrong voltage. In my case the B2B is set LiFePO4 and 14.6V which is higher than the engine battery needs.

 

[G7UXG]

Perhaps the most straightforward solution might be to disconnect the starter battery cable from B1 of the CBE. It sounds like this wire goes directly to the starter battery, through a fuse which is mounted at the starter battery end. Could this then be connected to the relevant terminal of the B2B?

When the split charge relay is activated (when the engine starts) then the leisure batteries wouldn't be connected to the starter battery, and wouldn't charge via that system. They would then charge via the B2B. Would this work?

I'm trying to work out what I'd lose by doing this. I don't suppose the CBE control panel would report the starter battery voltage, but a simple voltmeter could sort this out. Or, perhaps if the connector on the CBE circuit board that picks up this voltage is identified, could this be wired to the starter battery?

 

[Pausim]

Perhaps the most straightforward solution might be to disconnect the starter battery cable from B1 of the CBE. It sounds like this wire goes directly to the starter battery, through a fuse which is mounted at the starter battery end. Could this then be connected to the relevant terminal of the B2B?

When the split charge relay is activated (when the engine starts) then the leisure batteries wouldn't be connected to the starter battery, and wouldn't charge via that system. They would then charge via the B2B. Would this work?

I'm trying to work out what I'd lose by doing this. I don't suppose the CBE control panel would report the starter battery voltage, but a simple voltmeter could sort this out. Or, perhaps if the connector on the CBE circuit board that picks up this voltage is identified, could this be wired to the starter battery?

I think you would lose the mains charger trickle feed to the engine battery as well. Not sure how it might affect the 12V operation of the fridge, CBE is not very forthcoming with detailed wiring for the DS internals.

 

[G7UXG]

I think you would lose the mains charger trickle feed to the engine battery as well. Not sure how it might affect the 12V operation of the fridge, CBE is not very forthcoming with detailed wiring for the DS internals.

I've assumed that the cross-over relay that you've used effectively disconnects this starter battery cable from B1 of the CBE when the B2B is active, i.e. when the engine is running. Would this not have the same effect on the fridge? Your method still allows the starter battery to be charged (I assume) when the engine is off and mains is connected.

Might be a solution I could copy.

 

[Pausim]

I've assumed that the cross-over relay that you've used effectively disconnects this starter battery cable from B1 of the CBE when the B2B is active, i.e. when the engine is running

Yes. I used a changeover relay because I could not find a 4 pin normally closed relay of sufficient Amps but 5 pin ones are available.

Would this not have the same effect on the fridge?

Good point, I must check that. I only finished the installation a few days ago. Hopefully the D+ will still activate the 12V fridge connection and the charging leisure battery will keep the circuit live.

Your method still allows the starter battery to be charged (I assume) when the engine is off and mains is connected.

It should do because when the engine is not running the connections are the same as before adding the relay. No ehu at our storage site so not yet tested but I am not expecting a problem.

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[Wagoneer]

Well done Pausim for potentially cracking the B2B interface problem with the CBE system.

Initially, I was a bit concerned how this would affect the 12v supply to the fridge. However, I believe the 12v fridge supply is powered from the leisure battery and controlled on the CBE board by a relay, triggered by the existing D+ signal, which only allows 12v power to the fridge whilst the engine is running. The gas/EHU fridge functions should remain unaffected.

I guess your D+ signal for the Durite NC relay is wired directly from a D+ function on the B2B unit. I'm currently considering a Votronic 30amp B2B which has this feature.

I look forward to hearing of the final testing and pics.

 

[Pausim]

Well done Pausim for potentially cracking the B2B interface problem with the CBE system.

Initially, I was a bit concerned how this would affect the 12v supply to the fridge. However, I believe the 12v fridge supply is powered from the leisure battery and controlled on the CBE board by a relay, triggered by the existing D+ signal, which only allows 12v power to the fridge whilst the engine is running. The gas/EHU fridge functions should remain unaffected.

I guess your D+ signal for the Durite NC relay is wired directly from a D+ function on the B2B unit. I'm currently considering a Votronic 30amp B2B which has this feature.

I look forward to hearing of the final testing and pics.

I have a Votronic VC1212-45 but have used the settings to limit the current settings to 38A/42A so that they are comfortably within the wiring and fuse limits. Very pleased with the Votronic which worked well in my previous motorhome.

I would have used the simulated D+ Signal from the DS300 but the dealer had put in some extra wiring for me so I picked up the signal for the Durite relay from this. I think the DS300 simulated D+ signal must be there so that the D+ feed from the alternator is not overloaded by too many extra relays. My CBE manual is currently with my motorhome but the online one I found shows a fuse (3A) and terminals for the simulated D+ within the DS300. If the terminals are crowded then perhaps a piggy back fuse would fit.

 

[Poutie57]

I’ve been reading this post along with others on the sterling B2B correct installation with great interest trying to understand if I have installed mine too simply, everyone seems to talk about the D+ wire and ignition wire but where do I find these to even start to add a relay

 

[Pausim]

I’ve been reading this post along with others on the sterling B2B correct installation with great interest trying to understand if I have installed mine too simply, everyone seems to talk about the D+ wire and ignition wire but where do I find these to even start to add a relay

That depends on how the motorhome was put together and what components were used, CBE or Schaudt Elektroblock etc. However most of them will be using D+ or ignition/voltage sensing relays to trigger the 12V fridge and alternator charging of the leisure battery and it should be possible to track this feed down somewhere.

 

[andy63]

ive been reading the various threads on battery to battery installations, and beginning to get a bit confused .. not hard I know,,, but ive read a number of people posting that these units can be installed without going through whatever power management system you happen to have...and when Eddie from van bits is saying it doesn't pose a problem (and they must fit loads )why are folk still going on about the need to install large relays on engine run signals to facilitate or include or protect the psu of the van..
or are we looking to make life harder..

is it not a bit like installing solar without using the built in facilities on the van psu... it works and is often necessary because the built in units can not cope with the power that some choose to install..

the only reason I can think of is that any monitoring system for battery capacity may be bypassed , but when you are installing something that may pass currents far higher than the psu were designed for it would seem best to bypass them providing the above mentioned point on monitoring battery capacity don't cause a problem... you can always install your own battery monitoring system..
Andy

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[Pausim]

ive been reading the various threads on battery to battery installations, and beginning to get a bit confused .. not hard I know,,, but ive read a number of people posting that these units can be installed without going through whatever power management system you happen to have...and when Eddie from van bits is saying it doesn't pose a problem (and they must fit loads )why are folk still going on about the need to install large relays on engine run signals to facilitate or include or protect the psu of the van..
or are we looking to make life harder..

is it not a bit like installing solar without using the built in facilities on the van psu... it works and is often necessary because the built in units can not cope with the power that some choose to install..

the only reason I can think of is that any monitoring system for battery capacity may be bypassed , but when you are installing something that may pass currents far higher than the psu were designed for it would seem best to bypass them providing the above mentioned point on monitoring battery capacity don't cause a problem... you can always install your own battery monitoring system..
Andy

My B2B was transferred from my previous motorhome and installed in the new one by the dealer. It was wired directly to the leisure battery so the main power was not going through the CBE as recommended by eddievanbitz in another thread. However, I found that that the battery linking relay in the existing CBE system was opening a loop when the engine was running which meant that the B2B was back feeding to the engine battery and through that to itself. I was concerned that in so doing it would prevent proper management of my Li battery charge and interfere with the normal voltage of the engine battery.

I will try to explain the loop. Engine starts and engine battery feeds B2B at 14.2V, B2B activates and feeds leisure Li battery at 14.6V. Li at 14.6 volts still connected to CBE but because the engine is running the CBE has linked the two batteries so the 14.6V travels back down another connection to the engine battery and from there to B2B feed. One big loop. To prevent this loop I added a relay that cuts the back feed. Hope this makes sense.

 

[andy63]

Hope this makes sense.

Thanks for taking the time..
I'm going to study that and try and follow .. One day I might try and install a b2b ..cheers
Andy

 

[Pausim]

I have put a diagram together, hope it helps.

The CBE relay is normally open separating the batteries. As the alternator starts charging the D+ signal activates the B2B but it also closes the relay in the CBE, creating the loop. I have added a relay at the green star that is normally closed so that functions like the mains charger trickle to the engine battery go on as normal. However when the D+ activates the B2B and CBE relay it also opens my relay so that the batteries remain separated and no loop is created.

 

[andy63]

I have put a diagram together, hope it helps.

ive had a look and understand your concern.. I just don't see it as a problem.. has it actually caused you a problem or is it just you trying to avoid one.. not sure ..

I was concerned that in so doing it would prevent proper management of my Li battery charge and interfere with the normal voltage of the engine battery.

yes the cbe relay will link the batteries and while that is happening the battery voltages will mirror each other at say 14.6 volts.. that appears to be well within the b2b input range and shouldn't stop it taking its power from the alternator which its designed to do, and charge the leisure battery ..
the current flow from leisure to start through the cbe relay would be minimal , as the voltage difference between the batteries with engine running would not be large..

thats my thoughts ..
Andy

 

[Pausim]

ive had a look and understand your concern.. I just don't see it as a problem.. has it actually caused you a problem or is it just you trying to avoid one.. not sure ..





yes the cbe relay will link the batteries and while that is happening the battery voltages will mirror each other at say 14.6 volts.. that appears to be well within the b2b input range and shouldn't stop it taking its power from the alternator which its designed to do, and charge the leisure battery ..
the current flow from leisure to start through the cbe relay would be minimal , as the voltage difference between the batteries with engine running would not be large..

thats my thoughts ..
Andy

Yes I think it is a problem, though I agree the current flow may not be great.
1) The B2B should be monitoring the condition of the Li leisure battery not a combination of Li and lead engine battery (It is set up for LiFePO4).
2) The engine ECU should be monitoring the lead acid engine battery not getting a false reading of 14.6V from the B2B.
3) It is not a good idea to link batteries of different types.
4) 14.6V is too high for charging a lead acid battery.
5) I got some very weird voltage readings on my previous motorhome when I initially wired it up without battery separation (possibly a very confused smart alternator).

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[autorouter]

If you have a B2B there is no need for the CBE relay at all. Or the other relay at the green star. It's just shorting across the B2B and negating its function. The whole point of a B2B is that it puts a different voltage on the leisure battery than the starter battery. Connecting a loop between the two equalises the voltages again.

What is the problem with simply breaking the loop at the green star where you put the extra relay? Does it stop the starter battery being charged on hookup?

 

[Poutie57]

What or where is the “green star”

 

[Pausim]

If you have a B2B there is no need for the CBE relay at all. Or the other relay at the green star. It's just shorting across the B2B and negating its function. The whole point of a B2B is that it puts a different voltage on the leisure battery than the starter battery. Connecting a loop between the two equalises the voltages again.

The OP raised a valid concern about the conflict between the B2B and the CBE split charge relay. I experienced the same problem. Yes removing the CBE relay would solve the problem but it is built into the DS300 distribution unit and can not be disabled without cutting out components and some people prefer not to damage the device.

What I have done with the relay shown at the green star is interupt the loop created by the CBE relay closing. The relay is a normally closed relay that opens at the same time as the B2B cuts in and the CBE relay closes. As I have wired it the leisure battery is showing 14.6V and the engine battery 14.2V when the engine is running, which is how it should be. Before I added the relay I had the problems listed at post #25 above.

What or where is the “green star”

The green star is just a symbol I added to my wiring diagram at post #23 above, to show where I had inserted the relay into the wiring. My post at #8 above is a written explanation of what I did.

 

[autorouter]

Yes removing the CBE relay would solve the problem but it is built into the DS300 distribution unit and can not be disabled without cutting out components and some people prefer not to damage the device.

OK I see the problem now. The wire from the DS300 through your extra relay is dual-purpose, and connects the mains trickle charger when on hookup. You can't simply disconnect it. The extra relay, controlled by D+, solves the feedback problem while leaving the trickle charger still functioning.

 

[G7UXG]

Pausim Interested to know how you've connected the fairly heavy cable that comes from the starter battery, to your new relay, and the relay to the B1 terminal. The relays seem only to have spade terminals. Are they adequate for the job?

For the few occasions that I hook up to mains, I may just keep it simple and isolate that cable from the CBE with a manual isolator switch.

Still thinking of fitting a Votronic triple unit that handles the whole lot (B2B, mains and solar). Only problem is, if everything is in one unit, if you goes wrong then none of it may work. But it can be quickly disconnected and the isolator switch connected to revert the whole system back to standard factory fit very quickly.

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