Hi Mick. It may have something to do with the battery charge capacity. My Canon battery for the 50D has almost half the charge capacity of one I bought from another maker, Yet, the Canon one was more expensive to buy in the same shop. :shock:
I bought two hahnel batteries for my 5d (I use the battery grip) last year in Conns. I went in looking for the Canon bp511 but the salesman put me on to these and they were a lot cheaper. As I needed extra batteries for a job I was forced into getting them and I thought that the shop were just pushing them because they were probably working off a better profit margin.
I needn’t have worried, they are outperforming my original bp 511 as promised and are great batteries.