Re: Power Draw

[adt22-at-drexel.edu]

Some guy on an RC boat list told me to use 24 gauge wire to limit the current draw 
on my EV warriors.  If I ever find that son of a gun! . . . 

----- Original Message -----
From: Frank Pittelli <frank-at-rctankcombat.com>
Date: Saturday, September 18, 2004 10:21 pm
Subject: Re: Power Draw

> randall b reynolds wrote:
> >  
> > HI everyone, I'm at the point in construction where I'm starting 
> to 
> > think of wiring and a speed controller. I checked a book out of 
> the 
> > library called "complete combat Robots". It has some formulas to 
> figure 
> > out Wire size , Amount of amp. draw from a dead stop and running 
> draw. 
> > Has anyone done this on their Elec. system, or have you used 
> past 
> > experience, maybe ?  Any help would be appreciated.
> >                                                                  
>            
> 
> When it comes to wiring, you can't make the main power lines too 
> heavy. 
>  Ev Warriors can pull over 70 amps -at- 12v when stalled, which is a 
> very 
> large current draw.  During normal operations, however, the total 
> current draw is less than 30 amps, but that is still worthy of 
> heavy-duty wiring.  For that reason, I have doubled up my battery 
> wires, 
> using two pairs of 10 gauge, stranded wire. (Stranded wire carries 
> DC 
> current much better than solid wire.)  Alternatively, you can use 
> 10 
> gauge wire that has twice as many strands as standard stranded 
> wire. 
> They sell such wire for high-power audio systems, I think they 
> call it 
> monster wire.  If I remember correctly, it has over 40 strands, 
> whereas 
> standard wire has less than 20. I also run separate supply wires 
> to each 
> side of my speed controller to reduce the current through each wire.
> 
> With large current draws, you also need to consider how all the 
> wires 
> are connected.  Conventional in-line power connectors, such as the 
> ones 
> used on batteries, are usually not rated for such loads, so you 
> have to 
> either double them up or connect the wire directly to a terminal 
> strip. 
>    Direct connections are best from a power perspective, but 
> whenever 
> you change batteries it is easy to hook them up backwards, which 
> can 
> lead to some nasty surprises.  For that reason, I use polarized, 
> double-up connectors for all batteries and I use large spade 
> terminals 
> and terminal strips for the rest of the wiring.
> 
> You'll also need to get a cut-off switch that is capable of 
> handling the 
> max current draw.  I use a 100 amp key switch that is normally 
> used in 
> cars to disable the starter battery.  They are very durable and 
> the key 
> is a nice bright orange so that you can easily spot it on the 
> outside of 
> the tank.
> 
> Finally, you'll want to include a high-amp, slow-blow fuse 
> somewhere 
> between the batteries and everything else.  I use an 80 amp fuse 
> that is 
> used for high-powered car stereos.  They come in different shapes 
> and 
> mounting fixtures, but they all do a good job of safely shutting 
> things 
> down if you short something.
> 
>       Frank P.
> 
>