I gotta say I've used B&D battery maintenance products before and have always terrible luck with them. It seems to power tools by them are Pretty good as the ones I have have been working well. However for the price you can't really go wrong, plus if it does break fast you can get another free...
For battery maintenance I use a minnkota battery charger/trickler. Had it for 5-6 yrs. Used it mainly for charging the trolling motor batteries on the pontoon boat I used to use, now I use it for my scooter's/auto's and it works great, although I paid $80 for it.