Might just nip out to the Co Op or Tesco and buy 2 packs of Duracell batteries then, might be cheaper and last longer.
They have battery extenders that you can precharge and take with you, in addition to the batteries that you can charge before you put them into your camera. That will close to double the time that your camera will last before you need another charge.
When I used to take a lot of photos, I got several sets of batteries to put into my camera, that way I could go for many hours before I used up all of my power.
The loss of time a rechargeable battery is not that great when you only use it one time. You can notice the shorter time the rechargeable battery lasts after you have been recharging it for a while, but when it got short enough to be annoying, I would just get more new recyclable batteries, precharge them and bring them along with the rest of the older batteries.
It costs a lot less to use recyclable batteries over time than to keep using regular batteries once and throwing them away. It is also a lot easier on the environment to keep recharging than to throw away one use batteries.
A specialized battery store near me says they have a new thing to recharge batteries, called a "battery conditioner". It has a little computer inside it that lets it fully drain the rechargeable batteries. This makes them last longer on a charge. I believe you can even recharge some regular batteries in a battery conditioner.
I plan to get a battery conditioner in the near future. They are not cheap, but sound worth it since the money it saves in battery longevity will pay for it over time. The battery conditioners do more stuff, but I do not understand it well enough to explain it well yet.