What is the smallest powersource i can use?

Hello everyone,
I have a question regarding the project I'm currently building:
As a scale modeller, I wanted a new challenge. That's why i decided to make an RC tank 1/35 scale.
I have a functional setup with my arduino, only the powersource is to big to fit in my model.
the components i am using:
-Arduino uno
-LN298N
-Bluetooth module HC-06
-Tamyia gearbox : Pololu - Tamiya 70097 Twin-Motor Gearbox Kit
-4x AA battery (series = 6v)

basicly my setup is like described here: http://www.roboremo.com/arduino-bluetooth-l298n.html

The only difference is; my power goes into the LN298n, which connects power to my arduino, which powers the bluetooth module.
This works, but I dont know if it's optimal. I have zero electronic skills, I'm glad I already made this work.

now for my question, what kind of powerpack is really small, and will be able to handle this setup?
After googling, I found that lipo batteries are pretty small. but what kind of voltage/current am i looking for. is A 3.7V sufficient, or do i need a 7.2?

any tips would be appreciated,
Cheers!

The L289 will not work with 3.7V. But there are many better chips with mosfets.
A lipo cell is the smallest.

Is the LN289n a better version than the L289 ? Do you have a datasheet ?

L298, not L289.

2S or 3S LiPo pack is obvious power source. You should probably forget the L298 as it is large and
may need heatsinking (which also takes up space and cuases issues).

Checkout some of Polulu's MOSFET motor drivers - no heatsink, much less wasted power (so longer
battery life).

MarkT:
L298, not L289.

Oops.

I misspelled the name of the motorshield, it is L298N.
this is the tutorial link at the product page of the website.

Thanks for the tips, ill take a look at those

And choose a smaller Arduino. My favorite is the Micro but a Teensy or Mini is even smaller. Minis are very cheap, but they require an external programmer, which makes it more expensive if you only need one.

That's why i decided to make an RC tank 1/35 scale

So what length will it be in inches? To save space I would consider using continuous rotation servos to drive the tracks.

I'll take a look at a smaller arduino, that's a possability, but also more difficult i guess. I was also hoping to put in a speaker at some point to simulate engine sounds, would a smaller arduino still have enough connections for that?

as far as the engine/gearbox is concerned, It is designed to fit in perfectly. It's not that big, but it slides in perfectly and aligns in the correct position. the tank kit is also from tamiya (about 20cm, that is 8 inches?), so i think the gearbox was also designed with this in mind (I read that tamyia was hoping to create a fanbase for 1/35 RC tanks, but it was discontinued, so some stuff is still for sale).

If you are looking to do audio playback.. then you'll have to add another board..

or at least other components (DAC, AMP...speaker..etc)

unless you only want to play TONES?

An Arduino Pro-mini is pretty small.. and costs rough $2-3.00 USD...

I picked up a programmer for it for like $1-$2.00 USD..