Battery for powering 4 motors?

I plan to run 4 Brushed DC Motor: 130-Size, 6V, 11.5kRPM, 800mA Stall on L293 arduino motor shield. I want to power them via the ext power connector on the motor shield. What type of battery would produce good results with this set up? What voltage battery should I look for? and type of battery?

In addition, I'm stacking the motor shield onto a arduino uno which is power by a separate battery source. I know that I need to remove the power jumper on the arduino to use two separate power sources for my setup. But what are my options for "removing" the power jumper? I'd like to use this power jumper in the future for other projects, so I'd rather not just cut the terminals of the power jumper. Any suggestions? Thanks!

First check the L293 datasheet for its voltage drop; iirc it's about 2V, so you should probably look to putting about 8 in to get 6 out.

Is it cast in stone that you use an old technology like the L293? Maybe have a look at this list of Pololu's for some inspiration. If the "za" on your name means South Africa like mine, have a look here if you don't know these guys already.

What voltage battery should I look for?

That depends on how fast (RPM) you want the motors to spin. The speed is roughly proportional to the applied voltage, viz half the voltage = half the speed. The motors are also more likely to burn out if stalled on higher voltages and will have a shorter life due to increased arcing at brush to commutator contact point.

and type of battery?

That depends on the motor load and how long you want them to run for before changing/charging the battery. If you put a load on the motors and all four take 400mA each that is 1.6A total, so a set of 4 AA Alkaline cells may last say 1 hour. Alkaline batteries are 1.5V each so start with 4 off, this type of batteries loses voltage under load and as they discharge.

NiMh rechargeable AA cells typically have a capacity of >2000mAh, so would run for an hour and can then be recharged. NiMh cells are about 1.25V each, 4 off in series would give 5V and 6 off about 7.2V. NiMh batteries can maintain a steadier voltage under load (lower internal resistance) so are good for motor driving. Of course you have the expense of a charger but if the motors will be run for many hours this may be cheaper in the longer term.

You will lose some voltage in the L293 depending on the load (current flow), an extra cell would compensate for this.

Out of interest.... what are you powering with the motors?

Does battery weight matter? if so then Lipo batteries with 2 cells would provide about 7.4V, these need a special charger and this option would be more expensive.