After doing a thorough research on the net regarding battery chargers, I got the following points that should be kept in mind while buying a battery charger:- 1. The battery charger should be a Smart/Intelligent charger (It simply means that the charger should be capable enough to sense the status of the battery inserted in charging. i.e., if the battery is a "non-rechargeable" one it should signal and stop charging. If its a "rechargeable battery" then it should sense the status of the battery as to whether it has completed its life or can it hold charge. If the rechargeable battery is new or not too old then it should charge it as required. It should sense how much charging needs to be done. If we mix batteries charged at different times and has different levels of charge left in it, then the charger should charge the battery as required. Not that it treats all the batteries the same and charges them all to a particular time programmed in the charger. This will overcharge the batteries and shorten their lives. To sum up look for chargers that are smart and can sense the battery charge status by heat and time, and thereof automatically stops charging. 2. Always look for a charger that can charge batteries individually and not in pairs. At times u will be using only a single battery (like in the case with cordless/wireless mouse). When one battery is drained u can put it in charge and use the fully charged one. This way by the time the new battery gets drained u have a fully charged one ready. 3. Always keep in mind ur requirement as to where u r going to use the batteries. If you want to use them in high drain devices and u keep requiring them without much delay then i would suggest u to go for fast chargers (2-5hrs) or else go with standard (12-16hrs) chargers. I have given the charge time range as rechargeable batteries of different mAh are available in market. If u charge a 1000-1500 mAh rated battery in a fast charger it will take 2-3 hrs depending on the brand of battery or else if u intend to charge batteries of higher capacities say 2000-2700 mAh then they may take 4-6 hrs. In standard chargers the same principle works - more the mAh, more the time. But standard chargers are good for long life of rechargeable batteries. 4. Also keep in mind the type of rechargeable battery u require. There are "high capacity" batteries and then there are "multi-use premium." High capacity batteries can be found up to a capacity of 2700 mAh (as of now) whereas multi-use premium have a maximum capacity of 2100 mAh. If u r using a high drain device then high capacity batteries are advisable otherwise multi-use premium rechargeable batteries are the best as you can charge them for more than 1000 times, whereas high capacity rechargeable batteries doesn't last the half life of multi-use premium batteries. These batteries are more eco-friendly. NB: Multi-use premium rechargeable batteries come pre-charged and can be directly used in devices and they even have better properties to retain charge if kept unused for a long period; the charge loss is negligible. Whereas on the other side high capacity batteries don't come pre-charged and have to be charged full before use. They even don't retain charge if left unused for long periods of time. My review on Sony BCG-34HW2KN As I had no other option, i settled down with the best i could locate in the market/flipkart. This charger is semi smart/intelligent. It can charge batteries in single, taking away the pain of having to charge compulsorily in pairs. As for the semi smart part it detects dead and non-rechargeable batteries. It has auto cutoff timer of 15 hrs. Had it the intelligence to charge the batteries as per the battery's charge requirement without overcharging them then i would have rated it with 5 stars and would have put it in the smart charger category. I was looking for BCG-34HRE4KN or BCG-34HRMF4N but could not find them so settled down with next best being BCG-34HW2KN

I have bought this product nearly 1 month ago for my Dell WM112 Wireless Optical Mouse (Black), which needs one AA battery to work. Before this, I used normal Eveready, Duracell like batteries, but nothing lasted more than one month. So, after 15-20 days, it became a regular routine to buy a new battery for me. But, this battery lasts more than one month. Also, everytime I have an instant backup battery and charging is easy. Hardly it takes one day. Only problem is there is no indicator to indicate whether the battery(ies) is(are) fully charged. But, other than that.. its performance is just what can be expected from any Sony product. Those who have a requirement of regular battery usage like me, this product is a must go..!!