I've found that that maplin rechargable 9v PP3 batteries last about as long as I need them to. I have a Status S2 Classic bass with an 18vdc active pick up system and an X2 rack mounted digital wireless system. The bass really isn't a prob (2 batteries will last for ages) but the wireless transmitter was eating batteries to the extent of about 4 per gig. However, using the maplin PP3's (fully charged) if I'm lucky 1 will last a full nights giging, 2 at a push, so in my experience (such as it is!!) those maplin rechargeables are worth a go!