Maintaining charge in 2 12v batterys

DIY
1

I have a 4 berth caravan and it is fitted with 2 x12 volt batterys. One 12 volt battery is charged by solar panels via a victron charge controller. Ive purchased a victron battery balancer. Can I use the balanacer to keep a second 12 volt battery topped up from the other battery and how would I wire them. The balancer I have purchesed has 24 volt on it but this requires 2 batterys to be wired in series.

2

No, because