External Chargers

[_luc]

I'm going to buy an external battery for peace of mind during the excursions.

I have found this: http://www.battech.co.uk/Device-Batteries-External-Batteries/c363_83/p1019/Universal-Slim-Line-External-Laptop-Battery/product_info.html and this: http://www.battech.co.uk/Device-Batteries-External-Batteries/c363_83/p1236/Universal-Mini-External-Laptop-Battery/product_info.html

Can I use any external battery which has 5V USB Output? Is it safe for my Kaiser?