Charging leisure battery.

I have a customer with a small chalet with no electricity. I fitted a
basic domestic alarm connected to a 75 ah leisure battery. What would

Why so large?

Thats what the customer has to be honest no other reason. But everytime
I do a load test it only registers about 40-50ah. Even after a full
charge.

You can realistically only draw around 35% of total capacity, so it's
functionally a 25AH battery. It's probably oversized, I would guess that
the actual requirement is closer to 8-10AH, but at least it will give some
headroom for a couple of days power outage.

be best to trickle charge the battery wind or solar power. Also the
charging device would have to be about 20-30 feet away from the chalet
because of tree cover. Any help much appreciated. Let me know if you
need more info.