# CBE DS300 split charge question.



## Nabsim (Dec 13, 2019)

I need to disable the inbuilt battery paralleling that is inbuilt in the DS300 junction/fuse box. From what I can see if I remove the D+ input from the DS300 this will stop the relay connecting both banks. Has anyone done this that can confirm what I think will work or not?

The idea is to do away with the split charge to fit a proper B2B dc-dc charger.

I am adding a shot of the DS300 layout, connector 18 has engine start sense on pin 1 and habitation battery charge start sense on pin 2, ignore text below. Where I have scribbled ‘cut out’ I mean remove the pin from connector block, failing that I will cut the wire as I can join again later if I am wrong.

There is nothing else going through the panel that needs the D+ connection here, it looks like it is purely for battery parallel connection.

Anyone know for sure?


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## QFour (Dec 13, 2019)

Just disconnecting D+ may leave it floating and could cause other problems. Usually D+ controls the fridge but on Uk MHs it can also switch the habitation electrics on and off. I found this on another forum.



> With your van having a CBE electrical system, don't forget to put in a heavy duty 5 pin relay in the original leisure battery positive cable to isolate the leisure batteries whilst being charged by the B2B.
> This should be switched by an ignition or D+ feed.


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## Nabsim (Dec 13, 2019)

QFour said:


> Just disconnecting D+ may leave it floating and could cause other problems. Usually D+ controls the fridge but on Uk MHs it can also switch the habitation electrics on and off. I found this on another forum.


It’s an Italian motorhome and habitation electrics stay on while control panel is switched on. I ‘think’ this is just going to stop the relay to enable what they call battery parallel, it may affect fridge 12v but not sure without trying it. I don’t think this will be a problem anyway though.

other ways I have seen to achieve what we are after is to snip a relay on the back of the control panel, don’t seem to be able to just pull a relay as it’s all integrated. My hands aren’t really steady enough these days to be soldering on circuit boards hence my preference to remove a wire.


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## QFour (Dec 13, 2019)

We have a Laika ( Italian ) there are lots of electronics that go with our CBE System. You need a correct wiring diagram to find out what is happening before you disconnect one wire and re-route the battery charging. You have no idea what will happen if you connect a B2B unit to the habitation battery. Perhaps an email to CBE might be a place to start.


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## trevskoda (Dec 13, 2019)

If working leave well alone.


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## Nabsim (Dec 13, 2019)

I have some info on what's fitted, from what i can find on the net there isn't much change of getting any info from CBE. Looking at it more though first thing I will try tomorrow is pulling fuse 10. I can check what's happening with a multimeter and it can't do a lot disconnecting the D+ feed. 

Your Laika probably has a couple of extra boxes that this one doesn't have, if so in one of them is a fuse that can be pulled.


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## Nabsim (Dec 13, 2019)

trevskoda said:


> If working leave well alone.


Not that straight forwards Trev, I dont want the battery balancing (spilt charge) connected when had battery is Lifepo4 and starter battery is a Varta then we put a 30amp B2B in line. I dare say the Varta can withstand 14.6 volts for a short time but not sure its a good idea to leave it like that, besides the starter battery will potentially be getting the Lifepo4 charging profile and it wouldn't like that outage for long.


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## trevskoda (Dec 13, 2019)

Nabsim said:


> Not that straight forwards Trev, I dont want the battery balancing (spilt charge) connected when had battery is Lifepo4 and starter battery is a Varta then we put a 30amp B2B in line. I dare say the Varta can withstand 14.6 volts for a short time but not sure its a good idea to leave it like that, besides the starter battery will potentially be getting the Lifepo4 charging profile and it wouldn't like that outage for long.


May take one of santas elves to sort that out.


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## genuis (Nov 29, 2020)

I had the same problem using a CTek 250SE DC - DC charger, it is explained in the manual of CBE PC 180 , you must cut resistor R37 on the DS300 board to disable the paralel charger relay, thats all , so simple


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## xsilvergs (Nov 30, 2020)

Nabsim said:


> I need to disable the inbuilt battery paralleling that is inbuilt in the DS300 junction/fuse box. From what I can see if I remove the D+ input from the DS300 this will stop the relay connecting both banks. Has anyone done this that can confirm what I think will work or not?
> 
> The idea is to do away with the split charge to fit a proper B2B dc-dc charger.
> 
> ...



I have an Italian van too, fitted with a Nordelettronica controller and similar issues to you.

I am considering a diode in the +ve from the Starter Battery. My thoughts are that this will take the Starter Battery voltage below the float voltage of the Lithium but keep the functionality of the controller intact.

The B2B can then charge the Leisure Battery but not back feed the SB or itself.

The only other job is to disconnect the fridge from the Nord's PCB. Then use the connector on the PCB to operate a relay to power the fridge direct from the SB.

It may work!


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## Nabsim (Nov 30, 2020)

This was on Charlie’s van and in the end we never fitted a B2B. Not sure how much charge came in from the split charge but it didn’t really matter as it ended up mainly static with Charlie mainly staying in the same spot for work and lock down reasons.


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## xsilvergs (Nov 30, 2020)

Nabsim said:


> This was on Charlie’s van and in the end we never fitted a B2B. Not sure how much charge came in from the split charge but it didn’t really matter as it ended up mainly static with Charlie mainly staying in the same spot for work and lock down reasons.



If you are replying to my reply, I don't know that I'd call it split charge. The idea of the diode is to stop the B2B from feeding itself and also charging the SB at a to higher (AGM) voltage and to create a voltage drop from the SB.


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## Nabsim (Nov 30, 2020)

I was looking at fitting a b2b but wanted to disable the split charge route. I had seen internet posts about fitting diodes and thought you were doing the same thing I was looking at, maybe not for same reasons though


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## xsilvergs (Nov 30, 2020)

Nabsim said:


> I was looking at fitting a b2b but wanted to disable the split charge route. I had seen internet posts about fitting diodes and thought you were doing the same thing I was looking at, maybe not for same reasons though



I had looked at disconnecting the D+ signal too. The Nord' PCB in our van powers side marker lights which receive a D+ signal, there may be other things too. 

Using the diode as I plan would allow a restricted charge of the LB should the B2B fail.


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## Okta (Nov 30, 2020)

I fitted a normally closed relay to the connection between the engine battery and B1 on the DS300. This leaves everything working normally except when the engine is running. I use the D+ signal to open the relay when the engine is running and this separates the leisure and engine batteries. In effect as the DS300 relay closes my relay openers and negates the link. I didn’t want to cut out the resistor because I might want to re-instate the original set up and CBE were not forthcoming about what else it might affect. My B2B output is connected directly to the leisure battery and everything is working well.

I think removing the D+ signal from the DS300 not only affects the fridge operation but the step out warning, which I believe is a legal requirement. The 3A fuse at 10 seems to be for the simulated D+ output at 12, this is so that the original D+ signal is not overloaded by all the additional requirements of motorhomes.


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## wildebus (Nov 30, 2020)

Okta said:


> I fitted a normally closed relay to the connection between the engine battery and B1 on the DS300. This leaves everything working normally except when the engine is running. I use the D+ signal to open the relay when the engine is running and this separates the leisure and engine batteries. In effect as the DS300 relay closes my relay openers and negates the link. I didn’t want to cut out the resistor because I might want to re-instate the original set up and CBE were not forthcoming about what else it might affect. My B2B output is connected directly to the leisure battery and everything is working well.
> 
> I think removing the D+ signal from the DS300 not only affects the fridge operation but the step out warning, which I believe is a legal requirement. The 3A fuse at 10 seems to be for the simulated D+ output at 12, this is so that the original D+ signal is not overloaded by all the additional requirements of motorhomes.


I don't know the DS300 unit (and while I have looked at the wiring diagram I can't remember the details), but I am just going to throw in a comment about the D+ signal and a different unit (yes, I know this thread is about the DS300, but loads of people may be reading this with interest but have a different system).

The Sargent equivalent units if wired as Sargent suggest do not rely on the presence of D+ on the Sargent unit itself to run the Fridge.  The same is true of the Step Operation usually and that is usually controlled by a seperate unit.
I know from removing the D+ input (referred to as "Engine running" signal by Sargent, but same difference) from the Sargent PDU on my own setup had no detrimental effect on either the Fridge Autoswitching to +12V running when the engine starts, and to the Electric Step operation - the warning still sounds and the Step auto-retracts.
FWIW, the "Engine Running" signal that goes to the Sargent PDU is actually the output of the Fridge Relay - so same as you comment about there being a 'simulated' D+ output, in this case it is actually a connection, via a Relay, from the Starter Battery rather than the Alternator D+ wire,  and it is that relay that is switched by the D+ itself.   The D+ line, as you say, can be overloaded potentially if not careful (it was originally only meant to light a little dash bulb was it not?) so some technique to simulate it is a good idea


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## xsilvergs (Nov 30, 2020)

Okta said:


> I fitted a normally closed relay to the connection between the engine battery and B1 on the DS300. This leaves everything working normally except when the engine is running. I use the D+ signal to open the relay when the engine is running and this separates the leisure and engine batteries. In effect as the DS300 relay closes my relay openers and negates the link. I didn’t want to cut out the resistor because I might want to re-instate the original set up and CBE were not forthcoming about what else it might affect. My B2B output is connected directly to the leisure battery and everything is working well.
> 
> I think removing the D+ signal from the DS300 not only affects the fridge operation but the step out warning, which I believe is a legal requirement. The 3A fuse at 10 seems to be for the simulated D+ output at 12, this is so that the original D+ signal is not overloaded by all the additional requirements of motorhomes.



Now I know I have a Nordelettronica control unit so different. There is the D+ signal in and this enables the fridge so should I need to control anything with a D+ signal I will use the fridge output. This is fused at 20A so plenty of power available for relays etc.


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## char21 (Nov 18, 2021)

Okta said:


> I fitted a normally closed relay to the connection between the engine battery and B1 on the DS300. This leaves everything working normally except when the engine is running. I use the D+ signal to open the relay when the engine is running and this separates the leisure and engine batteries. In effect as the DS300 relay closes my relay openers and negates the link. I didn’t want to cut out the resistor because I might want to re-instate the original set up and CBE were not forthcoming about what else it might affect. My B2B output is connected directly to the leisure battery and everything is working well.
> 
> I think removing the D+ signal from the DS300 not only affects the fridge operation but the step out warning, which I believe is a legal requirement. The 3A fuse at 10 seems to be for the simulated D+ output at 12, this is so that the original D+ signal is not overloaded by all the additional requirements of motorhomes.


This is an inspired idea. Can I ask is it all still working fine a year later? Did you just tap in to the D+ going to the DS300?  Thanks!


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## Okta (Nov 18, 2021)

char21 said:


> This is an inspired idea. Can I ask is it all still working fine a year later? Did you just tap in to the D+ going to the DS300?  Thanks!


Yes still working just fine. I picked up the D+ from another relay that was fitted for other purposes but otherwise I would have used the DS300 simulated D+.


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## johnuready (Apr 26, 2022)

How about setting the PV MPPT to lead acid profile and let the B2B charge the lithium leisure battery to the correct profile.


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## Okta (Apr 26, 2022)

johnuready said:


> How about setting the PV MPPT to lead acid profile and let the B2B charge the lithium leisure battery to the correct profile.


My set up does not include solar and MPPT. I have set the CBE mains charger to lead acid which slightly undercharges the battery but keeps it between 92% and 95%, which is fine when on an electric hook up. The B2B makes sure the battery starts off full when I am off grid when I need it to be.


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