View Full Version : Battery Cable Lengths

22 September 2010, 1901
I know it's advisable to keep battery cable lengths as short as possible to minimize voltage drop but if I want to locate some portion of my pack at the back of the bike, is that a problem? Is there a best way to split up the pack, or does it not matter? Or would it be better to build a pack for the back of equal size as the front pack and wire them in parallel?

Just wonderin'

Tony Coiro
22 September 2010, 2335
If you're worried about voltage drops, just use a larger diameter wire (smaller number AWG) If you are curious about how much power (voltage drop * amperage) you'll be dissipating as a function of wire length, voltage, amperage or AWG, here is a voltage drop calculator:


Hope this helps.

23 September 2010, 0613
Nice application Tony, but your link seems to be broken.

23 September 2010, 0638
It doesn't seem to know the difference between 0 and 00 gauge wire.

23 September 2010, 0656
Try -1 and -2

23 September 2010, 0745
That's very helpful Tony, thanks. It looks like it won't be a huge deal, but I will definitely want to use a larger gauge cable for anything I locate back there. Of course I don't yet have my final battery pack in this thing and already I'm developing schemes for more power... sick.

23 September 2010, 1545
Just remember to double the wire length in that calculation. Need to connect plus and minus.....
Also remember that every connection has resistance. Keep the number of connections to a minimum.

The total resistance of your entire current path can limit your maximum current. A 400 amp controller is useless if you have 2 ohms of total resistance in a 72V system for example. (72V/2ohms=36A !!!) To make full use of your controller in this example your resistance total cannot be more than 72/400 = 0.180 ohms. This resistance includes the motor winding, batterys, cables, controller, contactor, connectors, shunt and fuse. So keep those cable drops to a minimum resistance.

09 December 2010, 1501
Keeping that in mind - what are some guidelines of where to start in determining the gauge of wire to use between the traction pack, motor and controller?