If the LB is dead too then there is a fault.
The BM only feeds SURPLUS power and should protect the LB, but it was pointed out on here some while ago, that if the VB
drops it's voltage the LB may well effectively HAVE surplus and so feed it over.
drains if the alarm is switched on and the solar panels should be able to cover that drain, of course there are other drains on the VB
such as the clock and the radio. We found that WITHOUT solar input the Vb
could only power the vehicle for around 2 weeks "off charge".
Sorry, the answer is not quite so clear - obviously solar input depends on where the vehicle was parked and the weather as well as how big solar panel system you have.
Is there a fuse between the solar input and the LB ? If that has blown then in spite of any solar input at the charger it may not have got through. You may find it useful to check the voltage at the battery - it should indicate if the solar system is actually supplying power to the batteries.
Sadly, once a battery has gone flat it may well never recover as the plates in the cells may have been damaged - that could mean new batteries all round....
If needed buy those in the UK for de.ivery to a campsite or wherever you are staying - that is a MUCH cheaper option than buying in France, Spain or Portugal IMO.
We use Tanya Batteries whose delivery service has proved excellent and their prices the same.
Mr Google will find Tayna very easily - their batteries are suplied filled and ready to go, whereas batteries in France need filling with acid - adding to the expense and hassle. We got delivery within 48 hours....
Obviously a few MORE things to think about.....