I have just purchased a 100w fold up solar panel. It currently doesn't have a controler so I am looking to add one to it. I'm a little confused by the amp rating that I will need. I currently have a 100amp leisure battery. Have seen these on eBay just not sure if suitable. https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/233053091466 They do 40a up to 100a.