I've used the Ray-O-Vac 15-minute chargers with Ray-O-Vac 15-min NiMH batteries for two years; I'm a free-lance photographer and my wife is a full-time newspaper reporter/photographer; we both use them in cameras (except my Canon Rebel, which won't let me) and strobes, and I use them in assorted audio gear, recording devices, preamps, etc. We recharge at least two sets of four every day. Never had a failure yet, though I wish I'd kept track of the number of charges (how?) so I'll know which ones are marginal when one fails. We have six sets of four altogether, and three chargers, one for each car and one for the house. The charger has a fan in it to cool the batteries. I see Eveready has a similar unit now, but I've not tried it. I don't have any connection to any battery company--just a happy user. It's great to be dead certain that you have fully-charged batteries.
Dave Bovee, Saline, MI dbovee@sigmaplastronics.com