I had the SJ4000,one big problem is no spare batteries that fit
What had happened is the battery got down to 15mins life before going flat,i found a replacement battery and ordered it and it didn't fit.Was about 1mm too big,so i ordered a few more from different suppliers as they were cheap and same thing 1mm too big.Ended up making a dash cam out of it and running of the cigarette lighter and it worked great.
Still got those new spare batteries here and of no use.
Picture quality was great as a action cam just a pity about the batteries.
I was looking on line last week for another replacement action cam and noticed a ebay mob was selling the SJ4000 with 2 batteries so you may find they have replacement batteries to offer when needed at a later stage.Ask them first if you can buy batteries separately before placing a order on the camera.
Last week I ended up buying a used Gopro Hero 3 and got some spare batteries delivered today,at least this way i had a good supply for future use.
Hope it works out for you whatever you end up with