Thanks Steve, I understood bits like 'the', 'and',
battery etc. but I'm afraid the rest went waaaay over my head.

Hi Sharon, not at all! I'm as 'educationally challenged' [aka thick as mince ] as they come when it comes to physics, especially
battery technology, which is why I've gone into OCD mode to protect the M/Home! If you have a Vanbitz Relay, it allows for the Leisure
Battery ]'LB'] to pass surplus energy to the Starter
Battery ['SB'] AFTER the LB has become fully charged, which is often well into the day in Winter, especially in Scotland!
The AMT12 transfers current to the SB from the LB, even if the latter is still below 'full charge', effectively [in extreme cases] sacrificing itself by giving all of its available energy to the SB. So, on a Winter's morning, after a cold night, the LB can supply enough power to the SB to start the M/Home and get you going, allowing the alternator to start replenishing the SB as you drive. And then, when you park up, with luck, the
Solar Panel will be churning out leccy to feed the SB via the LB. It's like 'electrical courtesy', instead of the LB pushing to the front of the queue, it does a 'After you, I insist' and lets the SB have priority!
If the SB is at really low State of Charge, you can connect the prewired cable to Switch 2 terminal, say on the night before you need to start the M/Home, and the transfer of energy from LB to SB for 9 seconds in every 10 seconds will bring the SB back up to a level to start the engine in the morning
We have only on street parking, and the LB to SB transfer of power avoids the hazard of trailing extension leads and
battery chargers across the footpath to do what the AMT12 does
I cheated, and paid the £65 for the AMT12 plus cabling costs and labour, to have the work done by a professional, so that I didn't have to understand it fully, but just to use and enjoy it!
Steve