# Controller Connections



## TheSGC (Nov 15, 2007)

So how hot/warm should the B+, B-, M- connections be on a controller? I just did a 1 mile hilly run on my Kelly using 96 volts and I found the M- connection to be quite warm. I was thinking it might be a crappy cable, (which is possible because these are temporary ugly cables) but I want to make sure. I was probably pulling 100+ amps during the run and much more when trying out the acceleration.


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## Guest (Nov 8, 2008)

Do you have a proper heat sink on your controller to pull away the heat? I'm talking a big heat sink and not some wimpy one. The connections can be warm with that kind of amps. Mine never get so hot I can't touch them. I also have some old cable still in my system. Slowly being removed. Most of my cable is new. How did you do your lugs? Crimps? Got photos of your cables? I think the M- side gets a little hotter than the B+ side of things. 

Pete : )

Love pictures. 




TheSGC said:


> So how hot/warm should the B+, B-, M- connections be on a controller? I just did a 1 mile hilly run on my Kelly using 96 volts and I found the M- connection to be quite warm. I was thinking it might be a crappy cable, (which is possible because these are temporary ugly cables) but I want to make sure. I was probably pulling 100+ amps during the run and much more when trying out the acceleration.


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## Guest (Nov 8, 2008)

Had a gander at your blog spot. Interesting Controller set up you have there. Interesting way to hook up your precharge resistior and what the heck is that bit black box? Nice heat sink your using for your kelly. Do you have thermal grease between the controller and aluminum heat sink? Interesting cable set up too. Maybe your heat came from over taxing your controller with those hills. Is the amp gage reading the battery pack or motor? If the battery pack your controller is doing double duty or more. Pushing that kind of amperage is going to get things hot in a jiffy. 

: )


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## TheSGC (Nov 15, 2007)

gottdi said:


> Had a gander at your blog spot. Interesting Controller set up you have there. Interesting way to hook up your precharge resistior and what the heck is that bit black box? Nice heat sink your using for your kelly. Do you have thermal grease between the controller and aluminum heat sink? Interesting cable set up too. Maybe your heat came from over taxing your controller with those hills. Is the amp gage reading the battery pack or motor? If the battery pack your controller is doing double duty or more. Pushing that kind of amperage is going to get things hot in a jiffy.
> 
> : )


Ok the heatsink is a beast, the 11" diameter cutout from my 3/4" aluminum plate and I used a massive chunk of thermal pad for it. The heatsink itself was rather cool, and so was the controller, just the M- was warm, but still touchable. I don't have my AMP gauge setup yet, and when I do it will probably be for motor current. 

I don't think I taxed the controller too much because I never floored it up the hills, but I did during a straight way and it was fun. The tranny also slipped into 3rd gear when I wasn't paying attention and that alone will draw something like 120 amps on a straighway. (autotranny that I usually use in 2nd gear which should be more like 60 AMPS)

So it must be the hills creating the heat. Maybe I should add a fan cooling system too just to be safe. 

Oh, and the little black box is my mess of control circuits, relays and fuses that activate the controller and contacters when I turn the ignition on.


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## Tesseract (Sep 27, 2008)

TheSGC said:


> So how hot/warm should the B+, B-, M- connections be on a controller? I just did a 1 mile hilly run on my Kelly using 96 volts and I found the M- connection to be quite warm. I was thinking it might be a crappy cable, (which is possible because these are temporary ugly cables) but I want to make sure. I was probably pulling 100+ amps during the run and much more when trying out the acceleration.


The connections should be no warmer than the controller's heat sink or enclosure. That is to say, if the connections are noticeably warmer than the heat sink then it is either because the wires/bus bars are undersized (not to belabor a point made elsewhere...) or because there is too much resistance between the bus bars and the wire lugs due to corrosion, not enough torque on the bolts, etc...

One interesting thing to note is that the ANSI and NEC strongly encourage you to use plated copper bus bars (tin, silver or nickel* plating) if you want to run a reasonable amount of current through them for a given cross-sectional area. In other words, a plated bus bar is allowed to carry a lot more current than the same sized bare copper bus bar. This is mainly because copper oxidizes rapidly as temperature goes up and copper oxide is a poor electrical conductor, thus, the allowable temperature rise (from I^2R loss) is much lower for bare copper than plated.

* - note that gold is not recommended. Tin plating is the most economical and it will also sacrificially protect the underlying copper if it is scratched; silver plating will induce corrosion in the copper bus bar in the same situation but silver tarnish conducts just as well as silver. Btw, "Cool-Amp" does not deposit a thick enough layer of silver to be worthwhile but the "brush-on" silver plating solutions do.


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## TheSGC (Nov 15, 2007)

I think it's a mixture of the hills and the cable connections since they are copper pipes smashed onto the cables. I will be making new cables that are much higher quality and I will try to find some decent lugs for the controller connections.


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## Tesseract (Sep 27, 2008)

TheSGC said:


> I think it's a mixture of the hills and *the cable connections since they are copper pipes smashed onto the cables*...


*Oh*

"Well thars yuh problem..."


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## TheSGC (Nov 15, 2007)

Tesseract said:


> *Oh*
> 
> "Well thars yuh problem..."


LOL. I guess I took "temporary and cheap" to whole new level. Now I must find some lugs for my new cables.


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## 84bertone (Apr 10, 2008)

_So how hot/warm should the B+, B-, M- connections be on a controller?_


I made a 6 mile run with varying speeds up to 50mph. Ambient air temperature was 50 degrees F. I have a 96vdc system with LogiSystems controller. Car weighs 2340 lbs. Temperature on those 3 connectors were *85-87 degrees F*. About the same as the case temperature of the controller.


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## TheSGC (Nov 15, 2007)

84bertone said:


> _So how hot/warm should the B+, B-, M- connections be on a controller?_
> 
> 
> I made a 6 mile run with varying speeds up to 50mph. Ambient air temperature was 50 degrees F. I have a 96vdc system with LogiSystems controller. Car weighs 2340 lbs. Temperature on those 3 connectors were *85-87 degrees F*. About the same as the case temperature of the controller.


Ok, so that must be normal usage temperature. Mine was probably about that because I could still touch and it not get burned. I am still going to make better connections and an even larger gauge cable because I have a some.


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## Tesseract (Sep 27, 2008)

This is an excellent justification to buy one of those cheap infrared thermometers from Harbor Freight:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93984

$20?!

84bertone - a 30-35F rise is pretty low. Sounds like your system is humming right along. Did you apply any dielectric grease to the lugs before bolting them down?


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## 84bertone (Apr 10, 2008)

_84bertone - a 30-35F rise is pretty low. Sounds like your system is humming right along. Did you apply any dielectric grease to the lugs before bolting them down? _

No, I did not. I simply attached the lugs right to the terminals with good stout bolts and nuts. I used the hammer on tool to attach lugs to the 2/0 wire and it worked fine.


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## JRP3 (Mar 7, 2008)

Tesseract said:


> Did you apply any dielectric grease to the lugs before bolting them down?


Isn't the point of dielectric grease to stop current flow? If it's not conductive I see no benefit to putting it in between connections and in fact it would seem to be counter productive.


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## Tesseract (Sep 27, 2008)

JRP3 said:


> Isn't the point of dielectric grease to stop current flow? If it's not conductive I see no benefit to putting it in between connections and in fact it would seem to be counter productive.


Yeah, it does seem that way, and I still have a hard time with it myself but the rationale is that when you compress the connection the grease gets forced out except for the spots where the two connectors aren't in contact (we're talking about the microscopic level here). The grease then protects against oxidation from there on out. Note that you only use dielectric grease on high-compression-force fittings, or sliding contacts. Typically this means circuit breakers in electrical panels (notice how they always have a little dab of grease on the contacts?) and mechanical connections (lugs, etc.) of wires larger than 10ga. or so. Wires smaller than this you only smear the grease on the *outside* of the connection because there might not be enough force applied when compressing the connection to squeeze the grease out where the two surfaces might otherwise meet.

I live near the ocean so the results of greasing versus not greasing connections is pretty clear cut; YMMV.


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## JRP3 (Mar 7, 2008)

I thought there were other options besides dielectric grease for using on connections, depending on the connecting material. One is called Noalox but there are others: http://sw-em.com/anti_corrosive_paste.htm


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## Tesseract (Sep 27, 2008)

JRP3 said:


> I thought there were other options besides dielectric grease for using on connections, depending on the connecting material. One is called Noalox but there are others: http://sw-em.com/anti_corrosive_paste.htm


NoAlOx is a dielectric grease...  It has zinc particles suspended in it to protect against corrosion but not at a high enough density to be conductive.

The illustration on the above referenced web page shows you exactly why dielectric grease (with or without zinc) is good to use. Ironically, the author of said page exclaims that he can't see any benefit from using insulating grease between two connections, but can for zinc-filled greases like NoAlOx. He then goes on to explain that NoAlOx is actually no-conductive and that the zinc is only in it to provide cathodic (sacrificial) protection... It was good for a chuckle for me, anyway...


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## JRP3 (Mar 7, 2008)

Indeed, he does make your point quite clearly. I guess I should have read the entire page I linked for full understanding


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## Tesseract (Sep 27, 2008)

JRP3 said:


> Indeed, he does make your point quite clearly. I guess I should have read the entire page I linked for full understanding


Aw, it's no big deal. Even engineers still argue furiously about whether or not to use dielectric grease. Frankly, it is one of those things that really doesn't jive well with your intuition at first but when you consider things from a microscopic perspective it makes a lot more sense.


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## JRP3 (Mar 7, 2008)

I assume simple resistance tests of connections with and without grease have been or could be done to check it?


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## Tesseract (Sep 27, 2008)

JRP3 said:


> I assume simple resistance tests of connections with and without grease have been or could be done to check it?


While I'm sure *someone* has done this sort of testing, I couldn't find any results myself... 

Definitely worth doing, but there are two practical problems:

a) You need to run a high current through the connection to get a meaningful voltage drop and use "Kelvin" clips to do such.

b) You need to perform this measurement for a long time period to see if there is any difference in conductivity over time between coated and uncoated connections. Perhaps months or years of time depending on how abusive the climate is (Tampa, FL - abusive; Phoenix, AZ - not so much).

***

BTW - to do this test you need to make a very accurate current source to force a fixed amount of current through the connections then measure any changes in voltage drop over time.

Maybe I'll set something like that up and let it run in the corner of the shop for a year or two...


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