I run more than that (although motors are 6v) on a single 2S LiPo battery rated at 5000mAh. A 3S or even 4S LiPo should do you. The more mAh the better. Parallel them if you need more too.

You may need to provide an external 6V supply to the high torque servos though, I had issues with 2 high torque servos taking too much power and browning out the LCD.

How much time between charges do you average?

I have no idea.I charged it for the first time since getting it the other day, I'd had it for at least a month but only used it while testing so 15-30 minutes at a time, a good 10 times if not more, but without the motors going much... rough guess 5 or 6 hours, probably more.

If it's just the 2A hbridge running at full power you will use 2A per hour, so a 5000mAh battery will run that for 2.5 hours.

Read up on LiPos though, undervoltage is an issue, as is incorrect use and charge. Don't worry about the paranoid scaremongers, batteries used correctly never explode...

that sounds like it will do the trick!.....i've read some posts around this forum and the net from what i gather, you don't want the cells to go in the negative. and some people are afraid of them catching fire...lol. maybe it would be a good idea for a battery monitor alram. i have seen that you created a battery monitor script i'll check it out and do some reasearch....thanks for the help as usual rich . just out of curiosity, do you work in tech suport?....lol

I created a battery monitor circuit board too, although it's for a 2S LiPo which is 7.4v (8.4v fully charged) but it should be easy enough to do a 3S (12.6v fully charged) or 4S (16.8v fully charged) if you understand how it works (and it's pretty simple, 5 months ago I knew nothing).

I keep my cells above 3.3v when possible, I think 3V is the absolute minimum so it gives a little time for the robot to find the charging station and charge himself up (that part hasn't been done yet).

i'm curious as to how you have the docking station setup? i've seen your posts talking about making your robot charge itself, i didn't know you finished your setup though. very cool, i got to check that out.

my ultimate goal is my vacuum robot. i'm just working out the hardware side of things now "testing & mounting everything" this would be a good addition.

I haven't even started that yet, see the note after that sentence... That's coming once the robot is complete. There are a lot of ideas in another post that's kinda died a little but I will bring it back to life again soon. I'm waiting to see what DJ has planned for future updates too though as he mentioned something not long ago when encoders were being mentioned... which indicates to me that he may have something up his sleeve for the robot knowing where it is. That's half the battle.

that would be nice . i think thats the most difficult aspect of making a script for my project, or any for that matter. thanks again! :D