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[meridian84]

Hi guys
I just bought a motor for my model.
It is 12v. At no load it draws 2.6 amps but at maximum efficiency it draws 12.8 amps.
So what size battery am I going to be needing.
Common sense tells me 12ah, am I right or way off the mark?
Thanks in advance
Grant

[sparkey]

  Depends on what type of boat and how long run time you want,your battery 12AH will give about 45mins run time if load figures are correct,size of prop hull shape and weight of boat all have an effect on run time motor type and size also make a difference,I experiment with prop type,size and pitch to get the performance and run time I want,I use brushless motors now which also give a longer run time and more power for their size,if you belong to a club perhaps some of the members will give some help with this as there is always someone with knowledge of this matter or if you give details of your boat someone on here will give the correct setup also a photo would be helpful,Ray.        

[malcolmfrary]

The motor will likely be pulling less than the max in normal operating conditions, so if a 12A draw is budgeted for, run times "should" be longer than unmodified theory suggests.  The factors that sparkey mentions are all valid, but you have to consider actual use as well.