My MAHA charger is great quality. Here is what I'm getting when I soft charge these batteries(rapid charge of course would be somewhat less lasting) :
When using the 'Blue'(-ish?) Tenergy batteries in the Rayovac 300 on 'low' setting I get just under 3 days(~70hours constantly 'ON'), however the light given off at during the last day is VERY dim. When using the 'White' Tenergy batteries in the Rayovac 300 on 'low' setting I get nearly 4 days(~90hours constantly 'ON') and the light stays fairly constant until the last ~15 hours of so then it gets VERY dim.
If turning this Lantern 'OFF' at daylight and 'ON' at night then the Tenergy 10,000 mAh batteries can last significantly longer than my 'constantly ON' tests.
I believe the 'White' Tenergy D NIMH batteries have a slower discharge rate than the 'Blue', otherwise they are the same 10,000mAH rating. All that being said, I still would've expected a little more from these batteries on the 'low' setting with the Rayovac 300. I'm going to end up purchasing a couple more Rayovac 300 for spares along with the Tenergy batteries regardless in another few weeks.
**UPDATE** Jan 2014...
I've had 4 of these Lanterns and the rechargeable Tenergy D 10,000mAh batteries for years now and everything is still running strong. I've recharged my batteries scores of times and remain satisfied with my overall experience.
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I use this lantern with NiMH batteries and it works fine. Specifically, I use the Energizer AA Rechargeable 2200 mAh batteries or the Sanyo Eneloop AA 2000 mAh (I have multiple sets of rechargable batteries which I use for all sorts of things). I also use the AA to D adapters so the batteries will fit. The Sanyos last a little longer; probably because they are better batteries. Obviously, the AA rechargeables don't last as long as D batteries. I also haven't timed how long the lantern lasts with AA rechargables, but my best guess is about 10-15 hours. I hope this helps.
I use it with the Powerex 10,000 mah rechargeable D cells and it last just as long as the alkaline. I have used it for a week while camping and no problem. I also use a 12v D, C, AA, AAA charger with a solar panel to keep an extra set of batteries charged up and ready to go. No problems after a year of running this system.