DC-DC charger

[ginkster]

Where is your solar connected to? If it’s the DC-DC then it will (may!) provide a small trickle charge to the SB. See circled bit below from the instructions that are available in the 12voltplanet link posted by DXX above.

 

[Sasquatch]

I think solar connected to a Victron charger and then on to the LB.

 

[DXX]

The CTEK can only cope up to 23v (if it works at all on solar - can't get mine to)

True, that is the limitation, in the specification.