It's the chemistry. If you've ever taken careful measurements of your car battery's voltage, you'll find it's 12.62 volts (not 12 volts). There are actually six cells forming that battery, and each cell has a voltage of about 2.1 volts. It's the chemistry (lead acid) that determines the voltage.

A Nickel based cell has a voltage of about 1.2 volts. Alkaline is about 1.5 volts. The old cells we used when I was a kid are now marketed as "heavy duty". They're less expensive than alkalines but are a waste of money. The chemistry there is carbon-zinc, and they are also 1.5 volts.

That's because you're charging them too fast. Get a charger that regulates the current and you might get more cycles. I don't know if you could get thousands, though. ;-)

Yes, I know... that's the price you pay for not wanting to wait a night for a charge :)
BTW: I've used both the Rayovac 15-min IC-3 charger/rechargables and the Duracell 15-min charger/rechargables - the Rayovac's didn't last long; I'm still waiting to see how long the Duracell's last.

If you absolutely insist on charging them that fast, then you should make sure they are dead, or nearly dead, before charging them.

I don't know what IC-3 means, but if the batteries are nickel-based then the only way the Duracell might be an improvement is if it has a better way of sensing when the batteries are charged and then shutting down the current. If the batteries are getting warm when you charge them, then chances are they are being over-charged.

IC-3 was Rayovac's product line name for their 15-min NiMh cells that featured an integrated IC. The Duracell cells appear to be standard NiMh cells. Both charges feature cooling fans to cool the cells as they charge, and, as you can imagine, they monitor the current and temperature of the cells.

There is supposed to be a new type of Lithium Ion battery coming out that charges in just a few minutes and is powerful enough to run things like drills and saws. I heard about it last year, but haven't seen it appear on the shelves yet.

I'm looking forward to that, if it is half-decently priced. Do you have any links to it that we can see?

I think it was featured in an article in Popular Mechanics in one of last year's issues. I can't find anything else on it, so I'm guessing it hasn't made it out of R&D yet, if it ever will!

Hi, You are right about new batteries being hit/miss! I found this blog because my MX900 displayed low battery (after about 1 year). I put 4 batteries in and nothing. Put a few more in and nothing. That's when I found your post. Sure enough of the 7 Rayovac alkaline batteries, 4 tested 1.5 volts, 2 registered about .6 volts, and the other registered zero!

I know my voltmeter works because when I put the good ones in, the remote fired up! Thank you!