Can anyone tell me how to charge a Ford Tourneo Custom battery?

It’s a mobility vehicle, so we have electrical locks to keep a wheelchair in situ. When the battery charge goes below a set level a current limiter won’t allow the locks to release unless the keys are in the ignition. We don’t do enough miles to keep the battery fully charged.

I was hoping to top up the battery with a Halfords smart battery charger (because the vehicle is stop/start), but I don’t think I can get to the battery terminals without disconnecting the battery which then might require a vehicle reset...?

Can I use the jumper and earth point to recharge? Does this work?

Yes, use the positive terminal under the bonnet and the engine hook to the left of terminal for negative to charge the battery. 

Right, great.  However I’ve also heard Ford don’t recommend this as per this... https://vans.honestjohn.co.uk/askhj/answer/101530/how-do-i-charge-the-battery-on-a-new-transit-custom-

I take it a so-called smart charger would assess the condition of the battery before it tried to charge it...?

Does it make a difference as to whether I have one or two batteries in the van?

Thanks for the reply.

My focus battery is flat, is it safe to leave it charging on 'normal' charge overnight?