Powering a HEQ5 mount

[Nelson]

In the near future I am going to buy the above mount. I currently have a 7ah Skywatcher power tank but I'm not sure whether it will do. I aim only to run my mount and laptop whilst in the field and usually for about 4/5 hours. I have read a number of comments on various web sites and mostly they all say a leisure battery or car battery is the way to ensure your mount does not play up during the viewing session, so, not being electrically minded what do I need and from where? I'm sure I will need a box to fit the battery in, to prevent rain getting in but where from? Cables and connectors, tools Etc. Can anyone help please. In the future I will be doing some AP, hence the need for the new mount, the HEQ6 is probably the better mount for AP but the weight is something I would struggle with.