Re: [mowbot] motor power, induction charging

Dave Everett (Deverett nospam at
Thu, 26 Sep 1996 16:01:53 +1000

robin nospam at wrote:
> Dave Everett wrote:
> > If we can get 6v motors for all the drive components then we will get
> > almost double the amp/hour capacity for the same size and weight of 12v
> > batteries.
> Unfortunately, you only get to run for twice as long by moving half as fast:-)

The efficiency is better than 50%. I know what your saying, to move the
same force for half the voltage you need to double the current, it's
really more of a problem in a full power mode, if you can pulse-width
modulate the signal you get better performance.
> There are a few imponderables, but it should be easy enough to get
> an approximate idea. Assuming two motors, my guess is no more than 1 > amp per motor.

1 amp should be sufficient, my old Hero Jr consumed 1 amp and only hAd
one drive motor, but it could cruise up hill on my lawn (about 40 deg),
2 motors will provide almost twice the torque.

> > We don't need contacts, we could use inductive charging. The robot only
> > needs to be in close proximity to the charger (maybe a plate on the
> > ground).
> Unless you can arrange to have the two parts of the induction
> system interlocking so they make a pretty good magnetic circuit, the
> efficiency is terrible, so a simple plate is out.

Why? the robot would be capable of detecting the current transfer and
adjust it's position to suit.

Dave Everett                                Email: deverett nospam at
(c) 1996 - Copyright remains with the author unless explicitly stated