# Wire Sizing for Motorcycle Conversion



## Csecrist12 (Nov 22, 2019)

I am having some trouble with wire sizing of each component in my system. Some of the following is what I have:

Curtis PMC 1231C Controller
K91-4003 Motor: K91-4003 Motor
LiFePo4 Battery pack of 32S 15P (102.4V Nominal and 116.8V Peak Charged)
ZEVA BMS setup with 3 12 slot modules
Thunderstruck DC to DC Converter in replace of the Aux battery for my 12V units. TSM 96V DC-DC TSM48DC-DC

I have the generic wiring diagram from Curtis that I would like to follow:










http://www.thunderstruck-ev.com/Manuals/1231.pdf



My question is, what wire sizing should I use where? The unit I have is limited to 500 amps Max as per page C-2 in appendix C (Very last page of the manual provided).
I am starting the build and ramping up my fabrication here in the next few months and would like to to have this topic covered.


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## MattsAwesomeStuff (Aug 10, 2017)

Your diagram actually shows the heavier gauge wiring in bold. Those are the ones that have to be thick enough to provide 500 amps.

The others are just signal wires. Technically almost anything would work, your limit is probably mechanical strength rather than electrical conductivitiy. 18g wire is probably fine.

Who's giving you advice to buy LiFePO4 batteries like it's 2011 still?


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## Csecrist12 (Nov 22, 2019)

MattsAwesomeStuff said:


> Your diagram actually shows the heavier gauge wiring in bold. Those are the ones that have to be thick enough to provide 500 amps.
> 
> The others are just signal wires. Technically almost anything would work, your limit is probably mechanical strength rather than electrical conductivitiy. 18g wire is probably fine.
> 
> Who's giving you advice to buy LiFePO4 batteries like it's 2011 still?



I appreciate the feedback. What type of wire would be able to handle the 500 amps?

Also, I picked them up on a trade I had and couldn't pass them up since I had no money in the trade anyways. All the cells so far are good and should do the job just fine.


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## Frank (Dec 6, 2008)

4/0 would be safe... 

Sent from my SM-T380 using Tapatalk


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## MattsAwesomeStuff (Aug 10, 2017)

Csecrist12 said:


> I picked them up on a trade I had and couldn't pass them up since I had no money in the trade anyways. All the cells so far are good and should do the job just fine.


Cheap cells are best cells, can't argue with that. I to enjoy the thrill of a budget build.


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## Dcoxryton (Dec 29, 2010)

If you haven't sourced the wire yet, I am using # 2 for 600A. I have 3 battery packs, each puts out about 200A (all at 72V), and I have #6 to contactor. It is a 3 phase motor so #6 to the 3 phases. Mine is a motorcycle. The motor gets hot, but the cables work fine. It is watercooled, but I haven't hooked the water system up yet. That is going to be done this next week, it is getting hotter out here in the desert. DC current calculations are really tough to find a straight answer. I have been using #4 on a 400A motorcycle for 5-6 years dirtbike and no problem or even discoloration. The fuse I am using in the DC bike is #12 romex solid wire. I have only blown it once when a drill bit part shorted the B+ to grd. Worked like it should


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## Toastednow (Oct 16, 2021)

MattsAwesomeStuff said:


> Your diagram actually shows the heavier gauge wiring in bold. Those are the ones that have to be thick enough to provide 500 amps.
> 
> The others are just signal wires. Technically almost anything would work, your limit is probably mechanical strength rather than electrical conductivitiy. 18g wire is probably fine.
> 
> Who's giving you advice to buy LiFePO4 batteries like it's 2011 still?


Lifepo4 batteries have improved from 2011. There are lifepo4 cells with 160 wh/kg and 18650 and 21700 li-ion cells have exploded in prices. If you have space and higher weight don't bother you why wouldn't you go with lifepo4. Lifepo4 batteries are better for environment, they are safer, they live longer and many can be fast charged in half hour even with 4,2V for cell without decomposing electrolyte.


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## cricketo (Oct 4, 2018)

Dcoxryton said:


> DC current calculations are really tough to find a straight answer.


What is that supposed to mean ? Motor controller has two ratings - continuous and peak. 600A motor controller is about 200A continuous, unless overrated by adding cooling. Wire current ratings are given as continuous ratings, primarily based on the insulation type - that is the reason why some wire from different manufacturers of the equivalent gauge may have a different current rating. Typical 2AWG "welding" wire would be rated at about 200A (again, got to look at the specific brand for the reasons of insulation), which should be sufficient for 200A continuous / 600A peak applications. Then the other consideration is voltage drop - for vehicles with long cable runs got to oversize the wire if the room allows, so if you got a 200A continuous and 10+ft traction wiring, got to go with 0AWG or bigger if practically possible.


P.S. The topic is old, hopefully OP hasn't set his house or garage on fire yet.


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