The power cabling.
The power cables are the things you will make yourself, although they can be ordered. I like to make my own cables because you measure desired length and the angle of crimped lugs directly in your vehicle, make it one by one, see how it fits and make more cables considering position of existing ones. It's hard to describe process, but for certain it is almost impossible to tell exact length of each cable section for ordering all at once, without actually laying the cable where it suppose to be and marking the length to cut.
In my case I will be using AWG gauge 4 welding cable to route the battery to the inverter, Siemens 50 mm2 shielded cable to connect all 3 phases of the stator to the inverter output, and flat braided strips for individual cells interconnects.
I made the crimping tool from the large used cutters by welding extra metal onto its jaws and shaping it to match OEM crimped lugs. I prefer Siemens style crimp where one or two bumps on the tool smash the lug from one side, it is easy to accommodate smaller lug size by placing half round spacer made out of flat piece of metal onto the half-circled notched jaw. Hex style crimping tool works OK too, but every lug size requires own die for crimping, making the tool less universal and more expensive.
All power connections (actually all the connections for that matter) under hood should be water proof. Usually connectors, especially poorly crimped, define overall reliability of the vehicle, and usually are the most troublesome. Trust me, special attention while making cables will pay off by years of dependable service. And it is not difficult to make good cables. As always, having right materials and tools is 90% of the success.
Will start with battery power cable. A welding cable is often used because is made of many strands of fine copper wire, making it flexible and easy to work with. A cable with fewer strands of thicker wire (same crossection area), while little cheaper, is harder to bend and route in tight places. Nothing special here other than gauge 4 welding cable is used instead of usual gauge 2/0. The currents I see are 40A in average, so the cables can be sized accordingly. Below are a few photos illustrating how to make a proper crimp.
For the individual cells I made interconnects from a braided gauge 4 strips ("ground strips" sold in auto stores) with lugs crimped on each end. Finally, for the motor power connections, special shielded cable is used - this is relevant to prevent interference to the near by shaft encoder cable.
Use corrosion preventing compound (I used Noalox) and right crimping tool. I made my crimping tool from the large wire cutters. Also use the shrinking tube to seal out the connection with meltable sealing glue deposited on its inner surface - it makes really nice insulation and protects crimping point very well. So here is how the proper cable crimping should be made (interconnect strip shown as example, battery cable is the same):
Ground strips and lugs used for
First, make sure you cut right length pieces, considering lugs length.
Before crimping stick the ends of the strip into Noalox.
The lug is placed onto the braided strip and the barrel is about ready to be crimped.
Done. Extra Noalox is squeezed out of the barrel - exactly what you want (no air trapped, no moisture gets in).
Final result. The crimper profile is shown here too.
For the motor power cables, while crimping procedure is the same, assembling is a little more complicated. Besides the need to be a water tight connection on both ends, a good shielding is required to avoid interference with the motor encoder cable and with the inverter brains. PWM pulses of high current produced by inverter consist of high frequency harmonics easily emitted around, and without shielding each power cable becomes an antenna doing just that. On the battery side this effect is not so pronounced, although shielding of the battery cables as well wouldn't hurt. Since the battery cable HF emissions do not interfere with the inverter (and I'm not going to listen to AM radio), I'll leave the battery cables alone.
So, for the motor cables special feed through water tight glands should be used. For my cables each end will have 9 separate parts, 6 of which belong to the gland, 2 heat shrink tubes and the lug. 3 cables for the motor side will be needed (3 phases, remember?). The cable construction is as follows: outer plastic shell, poly film insulation layer, special paper insulation layer, braided tinned copper shield layer, thick plastic insulation layer, paper insulation layer, poly film insulation layer, inner conductor.
This time, the procedure is:
Clean outer insulation.
Cut the shield braid to the right length.
Special Teflon film and mylar layer are unwrapped so the central conductor is exposed for about 12 mm length.
The cable is prepared for assembly - this lug will be crimped on it.
All the parts the connector consists of.
Sequence of assembly.
Ready to be tightened. Make sure the shield has good contact with the metal ring.
Ready for Noalox and crimping.
Noalox applied liberally.
The lug is placed on the inner conductor of the cable.
Crimping is done
All the motor cables needed (the black one is shaft encoder cable)