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Im new to electronics. Im a freshman in electrical engineering and just trying to start learning some stuff on my own. I saw this https://www.sparkfun.com/products/11497  hexapod robot and I want to try and build it. I ordered all the stuff but I still need a battery to power it and Im not sure what kind I need.

Im using the spider controller recommended on the robot product page: https://www.sparkfun.com/products/11498 . With this controller it says to use 7-30V and 3A but Im not sure what kind of batter would put out that much power. Id prefer to use Sparkfun since I have a gift card for them but if there is another site that has to be used I can do that to.
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So, the controller can supply up to 3A, but that doesn't mean it will always need to do so.  However, I would look into some of the RC hobbyist batteries.  The Lithium Ion batteries are probably your best bet.  You can look on their websites for batteries, and just choose something that can supply at least 7V, and the biggest number of milliamp-hours (mAh) that you can afford and will fit on the robot.  From full charge, this means the battery can supply that many mA for 1 hr.  You might get better results from a higher voltage battery, so I would lean towards the 11-12V batteries over the 7.4V batteries.  Also make sure you buy an appropriate charger and take that into account for your budgeting.

I might also take a moment to read through their assembly manual for a battery suggestion.
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Those are a bit expensive for the chargers, but if its what I need i can get it. I was looking though and I was wondering if this would work: http://www.amazon.com/Tenergy-Li-Ion-2200mAh-Rechargeable-Battery/dp/B002Y2LJW0/ref=pd_bxgy_p_img_y

Its relatively cheap with a charger and if I need more volts I could buy two and connect em in series right? Sorry still not sure how to calculate all this power stuff, if you could help with that part too id appreciate it smiley-razz
« Last Edit: October 30, 2013, 09:09:29 pm by GrimmAce » Logged

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Sorry still not sure how to calculate all this power stuff, if you could help with that part too id appreciate it

Lets see if I can get this right;

Power is measured in joules (J).
But obvioulsy you can apply power over a long time or over a short time.

Energy is measured in watts (W).
A watt is a joule/s i.e. it is a measure of how fast power is being supplied.

Electric charge is measured in coulombs (C)

Electric potential is measured in volts (V).
A volt equates to a J/C

Current is measured in amperes (A).
An ampere is a coulomb/s C/s

From the above you can see that 1V x 1A
is 1J/C x 1C/s or 1JC/Cs or 1J/s i.e. 1W
(so volts times amps gives watts)

When looking at batteries you want to know how many amps they can supply for how many hours.



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When looking at batteries you want to know how many amps they can supply for how many hours.


Ah ok, so amp-hours literally means how many amp/hour it can supply til drained? So a 2200 mAh battery like the one I linked can supply 2.2 A for one hour before being fully depleted and needing to be charged? Does that also mean it can also supply a maximum of 2.2A or is there another way to figure that out?
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Lets see if I can get this right;

Power is measured in joules (J).
But obvioulsy you can apply power over a long time or over a short time.

Energy is measured in watts (W).
A watt is a joule/s i.e. it is a measure of how fast power is being supplied.

Power is the rate of energy delivery.  Power is measured in watts, energy in Joules.
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Power is the rate of energy delivery.  Power is measured in watts, energy in Joules.
- oops indeed, what a stupid mistake, thanks for correcting it.
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