This is really helpful if your doing a long car journey. It tells you when to stop charging the battery, unlike the official 3 pin plug charger for the w810i which doesn't warn you about over-charing. I have had this for 2 days now and used it once on a 2 hour car journey. So far no problems, good value for 1p too...
Upon first use charger did as expected and charged phone. upon attempted removal from my handset the retaining pins detached from the charger and stuck in my handset, these were only removable with a pair of pliers. Stay well away and buy genuine