View Single Post
Old 11-25-2007, 10:52 PM   #162 (permalink)
Batman Junior
MetroMPG's Avatar
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,274

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.07 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)
Thanks: 3,810
Thanked 6,688 Times in 3,467 Posts
SW skools me on the basics (I need it)...

Originally Posted by SW
I think that does count. It's the current thing to do.

I don't think jumper cables have enough surface area in contact with the battery cables to handle the current you'd need (even in a test). The clips will probably heat up, and may even burn them at the contact points (you might be shocked to find the battery terminals burned as well), but I may be wrong. Don't let this impede your progress, just keep an eye on it. I read about many EV builders who regularly check and tighten their battery terminal connections because of the effects the high current has on them. One of the advantages of going with higher voltage is lower current:

Volts * Amps = Watts (Watts law)

But you may not be able to change the top voltage your motor/controller can take, so don't get too wired about it.

The other potential problem is the voltage drop across the jumper clips in proportion to the current:

Ohms * Amps = Volts (Ohms law)

So you want to minimize the ohms (unit of resistance) wherever you can: thick cable, heavy duty terminal connections, high surface area connections to your controller, fuse(s), motor, kill switch (eventually), etc. Try to have as little 'etc.' as possible.
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: Oops, I did it again! Bought another cheap, 3-cylinder Mirage. Mods in progress...
Ecodriving test: Manual vs. automatic transmission MPG showdown

has launched a forum for the efficient new Mitsubishi Mirage - fuel efficiency info for Geo Metro owners - electric car conversion on a beer budget
  Reply With Quote