I used 6 aa batteries 4 are 2500 mah and 2 are 1300 mah but there were fully charged

And I don't think the batteries are the problem because it's working when I'm pressing test but when I'm trying both together it's not working

I still say it's your batteries dude... When you press test it is only driving one servo (less power needed)... When you close the control and press the Arrow forward button both servos attempt to move, then the disconnect... 2 servos obviously use more current than 1, right? Your batteries are not providing enough current for 2 servos...

Try this... Disconnect (un-plug) one servo and press the forward button (with just the one servo connected)... If it works... You need new batteries...

Just a tip you should never use "AA" rechargeable when using servos or any application that requires a lot of current... Use 7.4V Lipos or 7.2V NiMh rechargeable batteries instead...

@Richard R I use 2500mah aa rechargables, and the robot only slogs a little bit. But I agree, it sounds like his battery pack.

When testing, you can run both servos I believe. Press forwards test on 1, and forwards test on the other, running both at the same time, and see if it burns out. If not, its a bug.

You should never mix mah rated batteries in the same pack. The uneven discharge could be related to your issue.

If they are rechargeable NiMH, they should be OK running 2 servos with 6 of either mah rating. The nah rating tells you how long they will last, not how many amps they can deliver all at once. Rechargeable Alkaline can not meet the inrush current requirements and the EZ-B will brown out. Non-rechargeable Lithium AA's are OK, but wasteful. Alkaline are not. NiCD (if you can even still get them) can not meet the inrush current requirements either.

Personally, I think EZ-Robot should add a LiPo, Charger, and the Adapter plug to the Dev kit and raise the price accordingly. This issue happens too often. But you can get a 7.4v 2S Lipo at any hobby shop that sells R/C cars or planes or easily find them on-line in your own country and not need to pay the international shipping rates.

Alan

@MazeHorizonTech If you have "good" niMh "AA" then they will work of course... but even awesome, name brand niMh "AA"s will never provide the current and longevity Lipos, SLAs or Sub C niMh packs can deliver...

Personally I recommend not using rechargeable "AA" at all and I agree with Alan, a Lipo and recharger should be included in the ez robot dev kit...

With your battery configuration, the most current that you are going to be able to draw at any one time is based on the smallest battery cell that you have (1.3 A * the C rating of that cell). The way that the pack is configured is to increase voltage and not amps. The thing is that these batteries don't use C ratings so you would have to identify the manufacturer and see if they have a spec sheet for those batteries.

Example http://data.energizer.com/PDFs/NH50-2500.pdf

In any event, you don't have enough current or amps available for what you are trying to do. Its not the EZ-B, its the inrush of current needed by the servos that is causing the disconnect. This has been discussed many times in this community. Use the search feature and look up "Inrush Servo" and enjoy the reads. There is a lot of info available from many different users.

I also agree that the dev kit should include a battery but I think it has something to do with laws about shipping LiPO batteries outside of enclosures or something. It seems like this was mentioned by Jeremy or DJ before.

customs check lipo's more the one time averywhere

see link a bomb proof bag for lipo's,gets you thinking.

lipo bomb bag