As per the Jan 18 rules update on the Tamiya site:
The batteries that are allowed for the 2008 season are:
a. Sanyo NI-CD 2400, Sanyo NI-MH HV 3000, 3300 & 3600
b. Panasonic 3000 Ultra Metal Hydride, Panasonic 3000 Stock Metal Hydride
c. GP (Gold Peak) 3300 & 3700, 4300, 4700
d. Intellect Batteries 3600, 3800 and LRP 3700, 4200
e. EPIC 3800, EP 4600.
f. LIPO batteries are only legal for the following classes: F103-GT, GT-2, GT-3 and 4WD-Off-Road. At this point in time the only three packs allowed are the Orion/Peak Carbon Edition 3200, 3600 and Platinum Edition 4800.
g. Sport packs that are readily available at hobby stores are legal as long as they are assembled from the general hobby industry i.e. Orion, Peak, Reedy, Duratrax, Dynamite, Trinity and Hobbico etc.
There is no further distinction on batteries in the Mini section:
1. Any Tamiya M03 or M04 chassis car that uses the 60D size tire or smaller.
2. Tamiya Hop-Ops only.
3. No chassis lightening allowed.
4. A proper mini body must be used with its proper mini chassis. I.E. (A front wheel drive body must be used with front-drive chassis. A rear wheel drive body must be used with rear wheel chassis)
5. Cars may run any Tamiya tires designed to fit the "M" chassis as long as the tires and wheels conform to the scale look of the body and are no bigger than the 60D. Running 26mm sedan wheels and tires on a Mini M03 and M04 is no longer allowed despite body type.
6. 24mm wheels and tires are not legal.
7. Mixing tire diameter sizes to create overdrive and under-drive is not permitted.
8. Kit type closed-end-bell, silver can motors only. Mabuchi or Johnson motors must be used for this class at all times.
9. It is now allowed to use the maximum pinion gear size on all front-drive and rear drive Mini cars. I.E. 20-tooth on the M03 and 21-tooth on the M04.
10. Any Tamiya plastic or aluminum hop-op damper may be used.
11. Any Tamiya short or regular size hop-op spring may be used.
I am not actually familiar if they have revised it already..You can refer to their site for further info: