The battery is D-Li8, i've ordered a replacement one from eBay for a tenner, from some guy in hong kong! (his feedback is good).
I thought it was worth the risk seeing as its a third of the price..
Can you let me know what the battery is like - I was going to buy one yesterday - I have just purchased the Optio S4 camera and thought it would be a good idea - especially for £10.
Cheers
Marck.
NB I just bought a reader from 7dayshop for £9, and memory card (256mb Kingston) from valuemedia.com
I've just ordered an S4 from Amazon (£194) which I thought was pretty good. I ordered a spare battery for £13.82 from www.gogo-power.co.uk, who I've used before and I've found really prompt and good. I also got an SD memory card 256mb from www.mymemory.co.uk (who were recommended by a friend) and look like they offer really good prices - SanDisk SD 256mb = £46.
I got the camera case which Amazon offer at around £23 and is said to wrap around the camera and not let it rattle or shake avoiding scratching. All in all quite a good package I reckon.
Just remember that many of the cheaper and non-OEM batteries tend to have a lower capacity than the 710ma Pentax batteries, so wont last as long between charges
I own the s4 and bougth a battery froma guy in hongkong some months ago, paid abotu £11 and use it as a spare, had no problems with it holding charge etc, I would say it doesnt last as long but it's hardly noticeable.
Got my backup memory card & battery at the wkend!
The battery is fine, works great as a backup, and cheap at £8.90 incl. delivery from hong kong (only took a week to get to me).
Well worth it.