Whilst driving, does the 3 way fridge source it’s power from the vehicle or the habitation battery ?

[No-Dun-Roamin’]

I thought I knew the answer to this, which is that the fridge connects to the starter battery/ alternator while driving.

But now I’m not so sure. I now have a lithium battery and a Sterling Power B2B charger. When this was installed, I think, to disconnect the split charge relay, one of the connections to the CBE thingy was disconnected. I have an app to monitor the Lithium battery charge/ discharge rates. While driving, there is a 9 Amp draw from the leisure battery, which presumably, must be going to the fridge.

Confused, but looking for enlightened guidance . . .

 

[ManTheVan]

You might want to search for Pausim ’s thread on fitting a B2B. It involves installing a relay that avoids having to cut the resistor. Took a while to get my head around it, but his design is simple, works beautifully and I’ll forever be grateful to him for sharing.

 

[No-Dun-Roamin’]

Wow, your diagram is exactly what I want to achieve. My fundamental problem yesterday was that I just could not find resistor R37 to disconnect it, to properly disable the voltage sensing split charge function. My DS520-EX may be a legacy, or superseded model, with date circa 2013 or 2014. The diagram has a note saying it applies only to DS300 from 2019. It might be worth me contacting 12vplanet to see if they can provide a solution for my older unit. There were no components adjacent to connector where R37 is located. I looked closely but could not find an R37. I took some photos of my board, and although it is very similar, it is different. I can see that disabling the voltage sensing split charge function is fundamental to realising a good solution. I did not have these problems when the B2B charger was first installed, and I am now wondering that if the relay activates, the contacts might have arc’d or welded, if it instantaneously switched a high current between the batteries. The dealer sourced the ignition feed from the front of the vehicle as the B2B is installed under the bench seat, very close to the drivers seat.
I’m still awaiting delivery of the Sterling Power ignition feed relay which I was hoping to use to ensure at least that the fridge is only sourced from B1. I despaired though when I noticed that there are 4 leads going to the fridge and now unsure of which one to cut to route via the separate ignition feed relay.
I would be happy to replace the distribution board and upgrade with a later model, and will also ask 12vplanet, if the wiring would be a compatible plug in replacement.
Many, many thanks the1andonly for such great advice and direction.

 

[No-Dun-Roamin’]

I have just seem ManTheVan’s recommendation to find Pausim’s thread on fitting B2B using a relay, as an alternative to finding and cutting R37, which I will try to find.

The profound knowledge here is incredible !

 

[No-Dun-Roamin’]

Having looked at Pausim’s threads, if I interpret what he has done correctly, he has opted for a Victorian B2B in preference to Sterling Power B2B and his arrangement is in conjunction with EBL rather than CBE.

I have been further thinking, which I know is probably dangerous but . . .
So, if I cannot easily over-ride the “voltage sensing split charge function” would the following arrangement using the external ignition feed relay be a possible solution. (I don’t now see the logic why the dealer disconnected B1 from the CBE) but it may have been more logical to disconnect B2 instead. (If you were on grid all the time and did not need a B2, then I’m sure the CBE will still do whatever it has to do.)
If B2 was disconnected at the CBE, the B2B charger is hard wired to the leisure battery, so during travel B1 and B2 should take care of each other. So if I used the ignition feed relay, to disconnect B2 only while travelling, then this would effectively over-ride the CBE split charge function. Then when engine off, CBE has access to both batteries, but would then have hopefully no conflict, since the engine is off.
Does this look like a possible solution, or have a missed something, which may well be the case ?

I have just referred back to the CBE booklet and it says the “electronic battery separator device operates only if B2 leisure battery is connected. So by disconnecting it only while travelling, this should overcome the separator, without having to find or cut R37. Also with B1 connected to CBE, the fridge should hopefully source its power while travelling from it. Fingers crossed !!

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[JockandRita]

It might be worth me contacting 12vplanet to see if they can provide a solution for my older unit.

I can save you the time and disappointment, as I've already spoken to 12Volt Planet weeks ago, to enquire about diagrams for the older CS340/DS540, as I couldn't find the R37 resistor anywhere. No joy whatsoever.


TBH, I'd rather have a switch which would allow me to revert to normal charging, in the event of the Sterling B2B going belly up, however, with the relay installation, (same as Pausim Paul), if the B2B does malfunction leaving me without a charge, I just need to pull either of the two thin cables (and isolate it), to take me back to the original charging circuit.

A normally closed relay, (until the engine is running), as installed by a recommended Auto Electrician.....................

Cheers,

Jock.

 

[No-Dun-Roamin’]

Yes, defo, hopefully the way to go. I had ordered a relay which is 2 pole with normally open contact. I had realised that I would need to go for a normally closed relay which would open when ignition feed activated. So will order the 3 way relay in your photo. Many thanks . . .

 

[the1andonly]

No-Dun-Roamin’ This is view with resistor cut. On a 2017 model.

 

[No-Dun-Roamin’]

That’s what that corner looks like in my unit.

 

[the1andonly]

What did you do to R37?
Ah well thats dead in the water
Back to Pausim method.

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[No-Dun-Roamin’]

Just could not find R37, unless is it lurking somewhere on the underside of the board.

I think I have replicated Pausim’s method very successfully this morning. In the end, all it seems to involve, is disconnecting the B2B / lithium battery connection to B2 on the CBE while charging the lithium battery, I.e. while driving. I also reconnected B1 to the CBE.

Before that, there was a draw from the leisure battery, when I switched the fridge on. After that, their was obviously no draw from the leisure battery, but the fridge came on so draw was now obviously coming from the vehicle battery as it should.

Awaiting a double pole ignition feed relay, but could just as easy do it with a switch. When I reconnect the B2B / leisure side back to terminal B2 on the CBE, while the engine is off, both batteries read separately and all functions appear normal.

Sincere thanks to all for getting me to a robust solution. Will tidy up and complete when the ignition feed relay arrives. . .