* Prices may differ from that shown
Ansmann's extensive, "leading-edge" list of features on the Energy 4 charger is backed up by an extensively high price. The Energy 4, and the rest of the chargers in the "Energy" series, are clearly not meant to be budget chargers. Simply, they are marketed at serious users of rechargable batteries.
The Energy 4 is the smallest and cheapest charger in the "Energy" series. The others differ only by having more charging slots; otherwise features of each model are basically identical.
Ansmann includes a set of socket adapters for different countries worldwide, a nice addition, although it's not really a selling point. Before you can use the charger here in the UK, you must attach the right adapter. Unforunately it seems Ansmann made a design error because (at least on my version) the UK adapter results in the charger fitting in the wall socket upside down! Oops!
Nevertheless it charges batteries fine. Unlike cheaper chargers which use only a timer (an estimate), the batteries' voltage is measured throughout charging so it can detect almost exactly the point when your batteries are fully charged. This is really a feature worth looking for in battery chargers as Ni-mh batteries hate being overcharged.
It also means that your batteries can be charged more quickly (5-6 hours for a set of AA's, compared to 12-24 hours in timed chargers). There are faster 1-2 hour chargers around, but only the best of those charge so quickly without overcharging or overheating batteries. The Ansmann's charging time is an acceptable compromise. I should mention that it appears to charge newer Eneloop/Hybrio-type batteries without a problem, as should any Ni-mh charger.
Ansmann also included a "refresh" feature that is supposed to improve the life of old batteries and prolong the life of new ones. It activates at the beginning of every charging cycle, even for brand new batteries, which is a bit of a surprise and contrary to what's said in the manual. It wasn't able to revive any of my really old ruined batteries, it simply rejected them, but I expected that anyway since those were totally dead.
When you insert a battery, the charger gives you its approximate charge level. "Approximate" is an understatement though. Your batteries are basically "charged", "fairly charged" or "nearly dead". But it's better than nothing.
Far more useful is the fact that batteries are charged completely independently. In other words, you can charge as many or as few as you like, inserted at different times, and each will be charged to its own full capacity. This is much better than the most basic chargers that require you to charge 2 or 4 at the same time and stop all simultaneously, regardless of individual charge levels. However it is a feature found many mid-range chargers selling for less than this.
Unfortunately, it does come down to the price in the end. The £30 or so it is selling for is just going to be too expensive for all but the heaviest users of rechargeables, even when you consider the quality, well thought-out features and the 3-year warranty. At £15-£20, it would be much more reasonable, in fact I'd recommend buying at this price if you see it. But otherwise you can get a cheaper charger with most of the features (except the refresh mode) for a less cash.