Black shut off electric switch in Broadway EB

Can I ask advice please  
Due to lockdown for corvid 19 could some one tell me what I should do with black shut down electric switch for the van.
I have just had new battery fitted and it is fully charged.   Also have a solar panel.  At the moment no mains electric is going in the van. Upto now I have always left it alone as we have upto date used motorhome each month. 
Help would be appreciated 
Jama 

Hi I  plug my into the mains and leave it on for 24 hours
This keeps both batteries charged  with the smart charger.on a 2019 Broadway eb. No problem  so far .engine starts first time.motorhome has been off the drive  for  at least  8 months

You should have a Sargent EC500 system in your van so this advice is for that.

If possible, connect to an EHU for 24 hrs each week and the EC500 smart charging will charge both Leisure and Vehicle batteries and will not harm them.

If that is not possible, switch off the EC500 with the top LH black switch. This will stop any drain from the leisure battery and if you have one fitted, send all charge from a solar panel to the leisure battery. If your van has the 'red' position on the ignition switch, use that to disconnect the vehicle battery other wise remove the negative connection from that battery.

Given that your 2016 Broadway has a solar panel, that should be sufficient at this time of year to keep both batteries adequately charged (especially if the solar panel is the larger capacity one). You need do nothing. Do not select battery on the Sargent control panel (i.e. do not have the tell-tale blue light on): the current from the panel will be shared between both batteries, keeping them OK.

However, if it's possible to connect to mains, then as Mids says, a regular charge from the mains will be adequate.

I'm afraid I don't know what you're referring to as the "black electric shut down switch for the van." Is it on the Sergant box? A precise description, or better a photograph, would greatly assist. But be that as it may, I think you'll probably be OK by leaving well alone - as long as you've nothing running on the 12v system (such as an alarm or lights).

Cymro

PS: Having started to type above, I nipped out to my van to search for a black switch. Now I'm back and have sent this, I've seen Peter's. I have the 328, not the 500 system, so I have no black switch!  Hence this postscript.

Thank you all. I have a photo but I don’t know how to send it to the forum

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Is it like this:

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Yes. That’s it - the black button on the left
Thank You I understand now.