In combat robots the motors are slammed from forward to reverse then stalled against a wall. They repetitive ly have to accelerate drawing huge currents. On an electric bike it sees nothing like this it has to occasionally accelerate then go along at a constant speed, and it only has one of those motors, your talking about having 4! So although lithium ion are suitable for electric bikes not so much for our applications.
If each of your motors draws 60A at stall then you need a battery that can comfortably output 240A (4x60) at burst. I would go for a 5aH battery to supply those 4 motors, this can output 5A for one hour, or 10A for half an hour, or 20A for a quarter of an hour etc. so for the 3minute fight it can supply an average of 100A which should be adequate.
To find the max discharge rate of a battery you multiply the capacity (in Ah) by the discharge rate (in C). So you need a C rating of at least 48C (240/5).
To achieve this I think you need either a Hawker Oddysee SLA battery (very heavy) or an optipower Ultra 50C Lipo like this:
http://www.optipower.co.uk/Catalogue...cat=131&cnode=
This would be very light. You could if you wanted more voltage use a pair of the 4 cell optipower batteries in series.
If you only want to use 2 motors then you only need half the discharge rate in which case I think web some of the cheap hobbyking lipos could supply the current (as long as you choose very high discharge ones- they are always overrated) but I would still choose a 5Ah battery to keep the high discharge rate.
I would listen to someone else though about what capacity(Ah) you need for those motors as I have never used them.
Originally Posted by Max
I think perhaps thats something to look into if i do well in the events, or if enjoy them for that matter! (though i'm sure i will)
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