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Asked — Edited

Power Question

Is there any reason why I can't/shouldn't use a 12 volt battery with a DC to DC
converter set to an output of 7.4 volts? Physical size inside my bot isn't a problem.
A gel cell is common/cheap and has lots of amp/hrs.

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Synthiam
#1  
missing the most important variable... Amperage. What amperage is your converter?
#2  
@Steve.... Yes, the gel cell will produce a lot of current at 12V.... However, as DJ mentioned once it goes through you voltage converter will it still have the amps to drive servos? Without enough power the ezb will likely "brown out" and reset every time you try and move the servos....
#3  
A quick perusal of Mr. Google didn't answer my current question. (pun intended:)
How much does the MG995 servo draw under a reasonable load? And what is an EZB4 drawing while loaded with all the goodies? (worst case)
#4  
SteveB ... well I can tell you this... each power pin on the digital ports can handle a total of 5 amp continuous and I think 20 in a brief spike... Total amps through the board is 20 after that the main fuse blows... As far as the mg995 is concerned you'll probably have to pull out your multimetre and measure it...

For future reference here is the stats on the ezb4... EZB4 Data sheet
#5  
@Richard ...Wow! I had no idea we are talking that much current! I missed the ezb datasheet thanks for the link.
@DJ...I was looking at a 10amp supply. But i was just guessing that would be plenty. Sounds like maybe not.
#6  
I would say 20amp minimum for a power supply... The reason is... start up current in servos (and other motors) can be high... The "in rush" current in a servo may be as high as a few amps (to get it moving) but later settle to a few hundred mA... Multiply that by a dozen or so servos starting you can see how easily a 10amp power supply could (and will) "brown out" the ezb....
#7  
After looking at the data sheet on the ezb and your help Richard I see why you do what you do. Never played with servos before...Thanks for the help.