cable? 12awg, 14awg ...

[izeman]

hi

i drive a mac/puma with 1.500w max, on 12s, so about 30amp and an infineon eb209. i plan placing the controller under the saddle, and batteries within the frame triangle in the front. before the controller was near the battery so this couldn't be any problem.

battery packs are put in series with 14awg and in parallel with 12awg. then they are directly connected to the controller. now there is 1m of cable between those. i'd like to use 14awg but am afraid that voltage drop would be too high. same goes for cabeling from motor to controller (which is the original cable right now and has to be extended).

i thought of that cable: http://tinyurl.com/c3omgap

what do you think? am i overreacting?

 

[stewrobb]

For 1 meter of wire, the resistance of 12AWG would be 0.005 Ohms, for 14AWG it would be 0.008 Ohms. this may not be exact due to differences in the actual wire, but the ratio should be equivalent. For 12AWG you would get a 0.15V drop at 30A, and for the 14 you would get a 0.24v drop. Like I said, it depends on the strand count and other factors, but with the same type of wire, expect to see 60% more sag than 12AWG. Then you have to consider the resistances of the connectors and such, which won't change, so the actual difference will be much less. Depends how picky you are, if you can, just use 12, if there is a space concern or something else, it's not a huge deal. You won't even notice.

 

[Kingfish]

9C & Ebike-Kit hub motors have 14-AWG wires coming out of the motor, so I would tend to agree with Stewrobb that the difference might be subtle unless you upgraded all wiring. If possible, try reducing the amount of connectors between the batteries, controller and motor. On a side note, I do not care for the APP and prefer Barrel; the APP connectors have been frequently problematic in the past for me.

My ½ watt, KF

 

[SamTexas]

What they said.

what do you think? am i overreacting?

Yes! Seriously you're fine. Although the max power is 1,500W, that power level only lasts a few seconds while you're accelerating hard. After that it would most likely settle down to the [400 - 750 watt] range. But if you're one of those speed freaks who draws 1,500W cruising then yes, upgrade the wiring. Otherwise, just keep the wiring as short as possible and eliminate as many connectors as possible.

 

[ZOMGVTEK]

1,500W peak is fine with really thin wire. I was running 14 or 16 gauge for a year or two, on 48V of lead at 60+A. It got awfully hot up a hill, but it never melted. It was still thicker than the garbage wire that came with my 1000W hub. However, that wire DID melt.

Thicker wire is generally a better idea, but it should be fine.

 

[izeman]

... It got awfully hot up a hill, but it never melted ...

but getting hot means it burns a lot of power, doesn't it? i mean melting cables is a definite no go *ggg*
even hot cables imho is no good idea. so i may go for 12 awg.

 

[dogman dan]

I'd be inclined to wire the whole thing with 12g, and connectors that you can count on. But since 30 amps is not that much power, it doesn't have to be done immediately.

In other words, if you are going out to buy wire, go ahead and get 12. If you have the 14 g laying around the shop, you coluld use that ok. By 40 amps, 12 g for sure, but you are only pulling 30. If you do heat up something, it's more likely to be a connector. On my race bike, 110v 40 amps, 12 g wire gets noticeably warm, but doesn't melt. 3000 watts or so.

 

[johnrobholmes]

I would be inclined to wire the whole thing with 8 or 10ga. Or double the 12ga. I rewired the motor leads on my bike from 14ga to 8ga and the controller temps dropped over 20 degrees F. 35a/ 75a settings.

 

[Kingfish]

Small comment: For 8-AWG, using APP connectors at 75A capacity and below are difficult to assemble. I like the idea of doubled-up 12-AWG; good way to go if 10-AWG is short in supply.

OT: So guys… is that 3kW per wheel?
~KF

 

[izeman]

i have none of those cables laying around. a least not those lenghtes. so i have to buy all of them.
i measured cable coming from the controller: the seem to be 12 awg. but cables from the motor seem to be 14 awg.
can anyone confirm?

 

[Kingfish]

i have none of those cables laying around. a least not those lenghtes. so i have to buy all of them.
i measured cable coming from the controller: the seem to be 12 awg. but cables from the motor seem to be 14 awg.
can anyone confirm?

Can't confirm if we don't know what motor you are using... or did I miss that part?

~KF

 

[izeman]

I would be inclined to wire the whole thing with 8 or 10ga. Or double the 12ga. I rewired the motor leads on my bike from 14ga to 8ga and the controller temps dropped over 20 degrees F. 35a/ 75a settings.

will that be possible with the puma/mac motor? don't think so ..

 

[izeman]

i have none of those cables laying around. a least not those lenghtes. so i have to buy all of them.
i measured cable coming from the controller: the seem to be 12 awg. but cables from the motor seem to be 14 awg.
can anyone confirm?

Can't confirm if we don't know what motor you are using... or did I miss that part?

~KF

it was the 5th word in my first thread: PUMA / BMC / MAC , i bought the PUMA @grafsport.eu
should be a 12t wound. i did order the 200rpm version, but think i got the 250rpm one. i'm fine with that.

 

[Kingfish]

D'oh! My bad! Too much coffee, not enough food :lol:

I don't own one, but from the looks of it, I'd wager it's 14-AWG; that looks like the standard hub motor out-cabling. The insulation is pretty good for that gauge and can take a lot of abuse. I defer to others on the PUMA / BMC / MAC as to what max-wattage motors can take.

Thanks for sharing!
~KF

 

[johnrobholmes]

I would be inclined to wire the whole thing with 8 or 10ga. Or double the 12ga. I rewired the motor leads on my bike from 14ga to 8ga and the controller temps dropped over 20 degrees F. 35a/ 75a settings.

will that be possible with the puma/mac motor? don't think so ..

I didn't pull 8ga into the axle, but all the external wire from controller to motor got replaced. It is about three feet of run from the rear hub to the controller on the front forks.

 

[izeman]

i just checked cables coming from the motor. those are 16 awg at most. so 14 awg would be a HUGE improvement. but i can't imagine how those would fit into this small hole. no wonder that ppl tell that those melted (no @30amp though)

 

[johnrobholmes]

The hole of a plug, or the axle? You can keep the small wire inside the motor and just add larger wire between components externally.

 

[ZOMGVTEK]

Resistance is additive. You want to minimize it where you can, but replacing the wires in the motor can be quite a bit of work for minimal gains. You only really should bother when you want the absolute most you can get out of the motor, and you are already pushing it to the edge. Cut the phase wires from the motor very short, and run thicker wire right off the controller to them. The thinest wire in the system is probably going to be the weak link, but thats fine in most cases. Especially if you aren't running major power.

Run the largest wire you can everywhere. Most people leave the phase wires alone, and that way they act as a sort of temp gauge and fuse. It's not like if you replace the phase wires with thick stuff the hub will be more reliable. If you are burning up phase wires, you are damn close to burning up the motors windings.

 

[izeman]

Resistance is additive. You want to minimize it where you can, but replacing the wires in the motor can be quite a bit of work for minimal gains. You only really should bother when you want the absolute most you can get out of the motor, and you are already pushing it to the edge. Cut the phase wires from the motor very short, and run thicker wire right off the controller to them. The thinest wire in the system is probably going to be the weak link, but thats fine in most cases. Especially if you aren't running major power.

Run the largest wire you can everywhere. Most people leave the phase wires alone, and that way they act as a sort of temp gauge and fuse. It's not like if you replace the phase wires with thick stuff the hub will be more reliable. If you are burning up phase wires, you are damn close to burning up the motors windings.

that sounds like a good argument. better blow up some small cables as some kind of fuse before the windings get destroyed. (i still have a small 40a fuse directly behind the battery). i cut wires near the axles and will run 14 awg from the controller to the motor, and 12 awg from controller to the battery. this should do it for a 30a setup.

i still haven't found an answer for the maximum wire to fit into the mac's axle.

 

[izeman]

The hole of a plug, or the axle? You can keep the small wire inside the motor and just add larger wire between components externally.

axle. i will use goldies for phase wires. so no problem with the plugs.

 

[ZOMGVTEK]

30A isn't a whole lot of current. I'm running 6-7kW (60-70A @ 24S LiPO, 150A phase) into the stock phase wires on my 1000W GM hub. They get really hot when abused, but they never melted yet.

The thickest wire you can get to fit, depends on your skill, wire used, how much you drill the axle, the thickness of sensor wires used (if any), etc... At your power levels, unless you find they get burning hot, its probably best to just leave them stock.