After buying an R4 for my DSlite a few weeks ago I found that the battery just couldn't keep up with my gaming needs, saw this 1600mah battery on amazon for £2.40 and thought "what the hell, even if it's crap I've only spent a couple of quid on it"
turns out it's quite decent
the 1st charge only lasted about 2 hours and I was worried but now, after a few charges battery life is averaging at around 7 hours (high brightness) where it would have been about 4-5 before... so it's worth it in my oppinion