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Need More Power With The V4.

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Hello all, im am at my wits end. I finally get LeXI physically completed and now i try to wire her up to the ezb v4's. Im using 1 ezb v4 connected to only one arm for testing( just 5 servos). i connect them to d0-d4. I am using a regulated ac power source giving it 7.4v with a max of 5 amps. i connect to the v4 via my pc, i assign each servo with a widget and try to move 1 servo at a time for calibration and ..." My battery is low, My battery is low.." !? how can the battery be low when the power is a constant 7.4v at 5amps? im at a loss! i have been waiting to use the v4's so i didnt need to use regulators and with just the 5 servos it freaked. I reset it and tried again( i also lowered the required voltage level to 5v) and now no more low battery msg, now it resets. Im really at a loss for words. What am i doing wrong? The bot performed as in my early videos with the v3, how come the v4 is not matching or exceeding the v3?

the servos im using are: Power HD 1501MG Metal Gear Servo 60g/ 17kg-cm High-Torque

again im using a constant ac adjustable power supply at 7.4v and 5amp max.

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What do you have the battery voltage set at in EZB.

Start EZB and click on the settings icon next to the connect button.
You will get another screen pop up (settings) and click on the settings tab.
What do you have the voltage set at?

Hope this helps.


While the AC PSU may be constant voltage it sounds as though you are suffering a huge voltage drop when the servo is operated.

Measure the voltage between a ground and vcc pin on any digital port while you attempt to operate the servo, see what it says when it drops. Work out your voltage drop. That'll be useful to determine if you are pulling too much current with a single servo.


It's probably the max amperage of the board. Wire the servo power to the battery direct and the signal wire to the ez-b. Should get you enough power!


@technopro i might as well stay with the v3 if i have to direct connect power.

@herr ball the voltage is set to 5v

@rich voltage reads 6.25


So you have a voltage drop of 1.15v which may indicate that you are pulling too much current or that the length or cable is too long, or that the cable size is not big enough. I presume it reads 7.4v with no load?

Did the exact same setup work with the V3? If so, did it also work with the V3 with the Vcc for the servos taken directly from the regulator rather than the V3s Vcc pins?

Do you know how much current the servos pull when they are under load (measured not taken from datasheets/info online)? Also, are the servos capable of running on 7.4v? The information I have seem on them gives a voltage range of 4.8 to 6.0v.

To answer the question of why it's giving the low battery error when you move a servo is simple, because when you are moving a servo the voltage of the regulator under load is dropping by 1.15v down to 6.25 which is below the default set low battery level.

The solution on the other hand could be a number of things which will depend on the current draw of each servo.


Maybe your power supply is lying to you? Maybe it isn't able to supply 5amps... Can you replace it with a decent 7.2volt nimh or a 7.4v lipo?


Or try 2 batteries in series. Double the amperage.


You mean parallel, Tech... parallel doubles the amps, series doubles the voltage...


@Richard r and Technopro

used 3 lipos ea. 7.4v 3500mha. same result