Rayovac 15 minute charger?

Just saw this at sams club. $35 for the charger and 4 2000 mah nimhs. They also had an Energizer 30 minute charger as well. Are these worth the money or do they just cook the batteries?

The writeups for the Rayovac sound promising. Keep in mind though that to use the 15 minute charger you MUST use the batteries that come with it, as they are the only ones so far that are designed for that system. I'm guessing that any other battery will probably be a BAD idea!

Unless there is a standard developed for these 30 minute batteries, I'd say stay away from them. Considering how my Rayovac 1 hour charger cooked batteries, and how other people have actually reported their batteries literally exploaded, I can say I'm done with Rayovac. I have a lenmar Gamma Mach 1 charger which is a one hour charger, and it charges batteries without even making them scarcely warm. The rayovac on the other hand gets batteries so warm that you cant hold them without fear of burning yourself.

The Mach 1 charger also has a fan blowing on the batteries which helps. Anytime I hear about a 15 minute charger, I start running the numbers. 2000mah AA = 8 Amps+ for 15 minutes. Not good for the batteries OR it does not fully charge them in the 15 minutes. Some fast chargers bring them up to about full and then top them off over the next 5 or so hours. As a general rule, the faster you charge a battery the shorter its service life. Metal hydrides are VERY rugged though and do take this fast charging very well. Keep in mind too that a nicad has a "full charge" cut off of 115 degrees F where a NiMH cell can reach 140 degrees F and be fine. Metal hydrides do normally get hotter than nicads in a fast charge state.

I like my eggs sunny side up.

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Stefan said:
The writeups for the Rayovac sound promising. Keep in mind though that to use the 15 minute charger you MUST use the batteries that come with it, as they are the only ones so far that are designed for that system. I'm guessing that any other battery will probably be a BAD idea!

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YES!! The Rayovac charger is meant soley for the "15 minute charge" cells. Using any other type of cell would be very bad. I thought Rayovac was going to use some physical means to lock out other types of cells from being able to use the charger, but not having seen them I don't know how they would accomplish that.

I posted about these NiMH cells a while back. Each cell has a mechanical switch in it. As the cell reaches full charge, gasses begin to form causing the internal cell pressure to begin rising. This increased internal cell pressure pushes on a diaphragm which then opens a switch inside the cell - disconnecting it from the charger. The charge senses the disconnect and cuts off the current to that cell so that when the pressure drops as the gasses recombine, the cell will not start chrging again.

Actually this is an ideal way to sense full charge on a given cell, but time will tell if this implementation is reliable. (Like what might happen after a year and a few hundred charge cycles, if the switch should fail. Perhaps the charger has a high temp safety cutoff? Also, can the switch handle the kinds of current we here might suck out of the cell /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif without damage?).

I do believe the package said something to the effect that it would act as an overnight charger for old style nimh and nicd rechargeables.

Perhaps Rayovac has indeed given the 15 minute cells some mechanical feature (like a special contact ring or something) that allows the charger to discern whether a charge slot has a 15 minute cell in it. Pictures of the cells show an interesting black ring near the negative terminal - could be part of a setection mechanism. That way, the slot would either dump in huge amps for the 15 minute charge type or use a trickle style charge for any other cell placed into the slot. If anyone had these cells It would be great to see a picture - I couldn't find close up shots on the Rayovac web site....

I only looked at it though the packaging.
The negative end of the cells have a center hump similar but not as pronounced as the positive end.
This seems to trigger the charger.

I almost purchased one, but the charger with two cells is ~27 and 4 additional cells are ~13.
When I can get them cheaper, I may try them.....
Then again, do I really need 15 minute capable batteries?

Given that the energizer 1-hour charger roasts batteries, I'm wary of their 30-min one. As for the 15-min batts, hey, cool, but I don't need fast charge that bad ($$).

Ok, I need to pawn off my old 1.6AH batteries on someone, and go buy a wad of these... It'll give me an excuse for the upgrade. /ubbthreads/images/graemlins/faint.gif /ubbthreads/images/graemlins/drool.gif