what i personally would use when the robot isn't going to move (example: animatronics head) a power adapter >5A 12V, or qa standard ATX power supply using the 12V rails if you have alot of servos.

and if you need to be portable (example: riding robot) i should use a >6V >7A battery (if needed, a solar charger too) but i f you want to run more servos, you can add another battery to double the amps

(when i'll buy my battery, i'll buy this one: http://www.conrad.com/ce/en/product/250153/ , measuring 12A 6V, measuring: (W x H x D) 151 x 94 x 50 mm )

that's what i would do for myself~

Personally I am using one 2S LiPo battery rated at 5000mAh to run my Hearoid, so far I haven't had to charge it although it is only being used for testing at the moment. Edit: I plan to increase the number of batteries to at least 2. I am tempted to fit a riser and fit a further 3 too, giving 5 batteries at 5000mAh, so 25,000mAh which would last quite some time)

LiPo (Lithium Polymer) batteries offer the best power to weight as far as I found out. However caution must be taken when using them as misuse can, and will cause the battery pack to burst in to violent flames.

A 2S LiPo is 2 cells each 4.2v when fully charged, in series. This gives 8.4v when fully charged. They are rated at 7.4v though. They shouldn't be discharged completely as they will not charge again, they also should be balanced so you have the same voltage in each cell. There are a lot of technicalities with them but in my opinion are worth it.

Other common batteries are the Sealed Lead Acid types, 6v or 12v, multiple batteries in parallel will give a long time between charges (as with any battery).

You need to decide if you weight and size are a major factor, if they aren't then Sealed Lead Acid may be the ones for you. They are powerful, can hold plenty of charge and are cheap.

If weight and size are important then LiPo are very small and very light.

You can get, or configure most battery types to give a lot of power but the more power the bigger the battery.

You don't need to use 18v. You can use anything between 5v and 18v, the regulators will regulate the voltage down to 5v. The higher the voltage the more the regulators work, the hotter they get and the more waste energy. @DJ Sures recommends 7.2v RC batteries. But then it depends on what you are running too, if you plan an onboard PC or netbook you will want to power that, so will need bigger batteries and ideally 12v.

If you were to give details of your project, space available, function, accessories planned, drive type etc. it'll help advise which batteries would suit it best.

You will, however always find that different people will recommend different batteries as it is generally down to personal opinion. They all have good points and bad points.

Thanks Guys ! Appreciate your input alot

RichMR2, i am using the small wall-e push toy, i managed to pack in the EZ-B , camera etc. into such a small case. I do have the larger Wall-e but i just wanted to see if i could get the EZ-B into the small wall-e and i did.

Right now I have (2) battery packs with 6v on each one, AA's, of course they do not last long at all. They do not power the camera, just two arm servos, 2 drive servos, 2 neck servos and the EZ-B.

Just looking for a pack I can put on his back, and if not to thick I can double it.

In which case you are very limited to what batteries you can use. My LiPo wouldn't fit in or on Wall-E and neither would a small 6v 4.5Ah sealed lead acid.

You can get different capacity AA rechargable NiCd batteries although I don't know how great they will be. I know when I bought a load of my camera I had two different capacities.

You could try and find a smaller RC pack, a 2Ah 6v NiMh pack, or run 2 or 3 of them in parallel to increase the capacity. Something like the Tenergy 6V 2000mAh.

Don't forget Wall-e carried around his little backpack thing, build one and fill it with batteries

Thanks for the ideas RichMR2 !