B2B + Split Charge And Lithium - Help!

Victor And Margaret

Victor And Margaret

Joined
Jun 29, 2022
Posts
44
Likes collected
124
Location
Bishop Auckland, UK
Funster No
89,576
MH
Autocruise
Exp
2009
Hi,

We have a 2006 Autocruise Starspirit that I'm upgrading with a 280Ah Fogstar lithium battery + Victron 30A B2B & Solar. I thought (ha ha) that it would just be a case of removing the split charge relay to prevent the battery charging directly via the alternator. The system has 2 relays, one for the fridge and step and the other for the split charge. Unfortunately when you remove the split charge relay, the fridge stops working. Pulling the other relay also stops the fridge working and the step from retracting when the engine starts. Is there any way I can stop the leisure battery being charged via the relay and keep the fridge and step working?

Any advice would be greatly appreciated.
 
What is the make/model of the distribution/fusebox that distributes all the habitation supplies? What are those 2 relays you mention, are they the type labelled 'Boite Relais Securite', with a large and small fuse included? Is it possible to post a picture or two of your setup?

I'm sure it's possible to disable the split charge relay without disrupting other functions, but it often depends on the details of the particular setup.
 
Hi, thanks for the reply.

It's just 2 relays and 3 fuses on a separate tray in front of the battery. The charger/ distribution system is a Sargent EC200.
20230209_114119.jpg
 
You could try removing one of the fuses. In the wiring diagram there is a fuse on the connection from the starter battery to the leisure battery, it looks like the centre one of those three, but I think a 15A is a bit lower than what I would expect for the split charge function. Worth a try though. If not it might be one of the other ones.
 
I've tried that - all of them individually and the same things happen. There's a 20A each for the Vehicle and Leisure batteries and the 15A is for the fridge.
There's also a 20A fuse in the Sargent unit but that only isolates the mains charger.
As a last resort I can pull the fuse at the leisure battery end before driving but that's a total PITA and knowing me I'll forget at some point and bugger the lot up!
 
When I had a van with a Sargent unit I found the easiest way to disable split charge relay, was to put a "Normally Closed" relay in the 12v+ cable from Sargent to leisure battery, driven by the D+ signal. In this way when engine was started the connection was broken between Sargent and LB.
The B2B then took care of charging with engine running
 
Thanks Autorouter, Arthur 49 & Lenny HB.

I've sussed the problem (apart from me being a complete Muppet).
I didn't have a battery connected when I was checking for the charge voltage at the leisure end of the circuit. After putting the standard battery back in the relay kicks in for the fridge and step and it's all working.

Cheers!
 
Victor And Margaret said:
I've sussed the problem (apart from me being a complete Muppet).
I didn't have a battery connected when I was checking for the charge voltage at the leisure end of the circuit. After putting the standard battery back in the relay kicks in for the fridge and step and it's all working.
Click to expand...
So, did you have to pull a fuse to disable the split charging, and if so which one was it? According to my wiring diagram there's one fuse for the step power from the starter battery, one for the fridge supply and 'EMC' hab cutoff relay, and one for the split charge supply.

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No, I just took the left hand (top in the photo) relay out.
With a habitation battery connected, pulling the
left hand relay stops the charger but leaves the fridge and step working. Without the battery connected, neither of them work.
 

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