Best battery for Lego Mindstorms ?

Hello,
My son is in a Lego Mindstorms club in his middle school. They placed 10th this year at the State FIRST competition in Illinois.
Anyways, the Bricks eat batteries like they are candy, and as the batteries are draining the robots performance changes. Does anyone know the best battery for this type of application ? What we'd like to see is a battery that can supply a pretty constant current till a certain point, then falls off quickly.
We've tried Alk's, rechargeable Alk's, standard, ... They all seem to perform about the same.
Any suggestions of what to use or where there is a web site that shows the different battery performance information (I've search around a bit, but have not found any thing too useful).
Thanks...
--
Greg Deuerling
Fermi National Accelerator Laboratory
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Nickel Metal Hydride rechargeables or NimH work good for high drain applications. I use them in my robots. Good luck.
-Dave

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Try NiMH rechargeable batteries. Look for 2100mAh capacity or higher (AA size). You can get them in most stores for about $10 a four-pack or a little bit more packaged with the charger. I would recommend buying better quality charger, which will extend number of charge/discharge cycles you will get from the batteries, especially if you don't intend to discharge them fully each time. You can get good selection from these web stores:
<http://www.thomas-distributing.com <http://www.batteryspace.com
Paul.

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