I use dry cell car battery, gets better mileage.

I think I'll leave the "comment" to you all.

Here's the link to validate my claim. Yes, I do said that AA rechargeable is recommended over the Alkaline Cell for a reason~!

Unless you're questioning the validity of wikipedia.....here's the link:-
Play & charge Wiki

Notes taken from the mentioned URL

Battery packs

Battery Pack, Play and Charge Cable and Quick ChargerThe battery pack for the Xbox 360 controller is nickel metal hydride. The pack provides up to 25 hours of continuous gaming for the wireless controller. It is recommended in place of disposable AA batteries (which differ slightly in voltage). It also ships as part of the Play & Charge Kit and as part of the Quick Charge Kit. Third party rechargeable battery pack kits are also available.
Play and charge kit
The Play and Charge kit allows the controller to be recharged while playing a game by plugging the wireless controller into a USB port. The kit also includes the rechargeable battery pack. It should also be noted that the Play and Charge kit allows use of a wireless controller with the battery pack removed, however this can damage the controller [3]. Microsoft currently does not support it to be used as a wired controller, however it does transmit data letting the host know that it is a wireless controller via a Play and Charge kit.[4]; wireless is still used for data communication and the Play and Charge kit therefore need not be plugged into the console itself to function. Any USB port may be used for the player's convenience. The Play and Charge cable also allows automatic pairing of the Wireless controller with the host (i.e. an Xbox 360 or a Windows PC with the wireless receiver).

It should be noted that the play and charge kit batteries are generic 1300mah AA(LR6) nimh cells. Such cells are readily available in 4 packs up to 3,000mah. With 2,000-2,600mah batteries being common.

There have been notable issues regarding this item. Sometimes, after more than six hours, the charge light will still be red, and the controller will not be fully charged. It should also be noted that the black Play and Charge Kits charge faster than the older white ones.

I don't trust Wiki.
Wiki can be edited by anyone.

hi bro ... we're talking abt rechargeable battery for household electronic devices ... not car ...

NiMH = niamah?