# Alltrax 7234 Problem



## Hezsus (Oct 22, 2013)

Its wired exactly like this:
http://www.alltraxinc.com/files/Doc100-047-A_DWG-AXE-PermMag-wire-dia.pdf

my Reverse contactor has a 12v coil (it was cheap) so i have it engaging from the output of the main contactor through the FNR rocker switch, I have diodes but have not installed them yet, And I have resistors but I dont think they are necessary since the controller is not powered through the FNR contactor.


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## Hezsus (Oct 22, 2013)

i'm also having a pretty large voltage drop under heavy load, nearly 10 volts


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## major (Apr 4, 2008)

Hezsus said:


> Its wired exactly like this:
> http://www.alltraxinc.com/files/Doc100-047-A_DWG-AXE-PermMag-wire-dia.pdf
> 
> my Reverse contactor has a 12v coil (it was cheap) so i have it engaging from the output of the main contactor through the FNR rocker switch, I have diodes but have not installed them yet, And I have resistors but I dont think they are necessary since the controller is not powered through the FNR contactor.


If you have the F/R contactor coils wired per that diagram (which doesn't show F/R contactor coils) and say you have them powered from the main contactor, then when your throttle microswitch opens up the coil supply for the main contactor, the F/R contactor coils lose power and resort to the NO position. The NO position on the F/R contactors short circuits the motor. Being a PM motor, this means shorting the armature which still has a constant field from the permanent magnets. That is a very strong brake.

I'd move the contactor coil power supply off that micro switch.


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## Hezsus (Oct 22, 2013)

major said:


> If you have the F/R contactor coils wired per that diagram (which doesn't show F/R contactor coils) and say you have them powered from the main contactor, then when your throttle microswitch opens up the coil supply for the main contactor, the F/R contactor coils lose power and resort to the NO position. The NO position on the F/R contactors short circuits the motor. Being a PM motor, this means shorting the armature which still has a constant field from the permanent magnets. That is a very strong brake.
> 
> I'd move the contactor coil power supply off that micro switch.


Great explanation, thank you, makes perfect sense, so my f/n/r microswitch should remain under power when throttle is at 0%, I will run the power for it through the key switch rather than through the main contactor. 

Is it bad for the motor to apply throttle when the F/N/R contactor is in the NO position (I do this for programming the controler.. so not often just dont want to burn anything up) 

Is it worth my time adding diodes/resistors to the f/n/r contactor? 

And is my voltage drop acceptable? aprox 10v drop, according to the controller under moderate to heavy load

Thanks again for the great reply


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## frodus (Apr 12, 2008)

You don't need precharge resistors on the FNR contactor, but DO install the diodes. Install diodes and precharge resistor on the main contactor.


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## major (Apr 4, 2008)

Hezsus said:


> Great explanation, thank you, makes perfect sense, so my f/n/r microswitch should remain under power when throttle is at 0%, I will run the power for it through the key switch rather than through the main contactor.
> 
> Is it bad for the motor to apply throttle when the F/N/R contactor is in the NO position (I do this for programming the controler.. so not often just dont want to burn anything up)


If the F/R contactors are both in the NO or both in the NC positions, the controller output is open circuit. So that should do no harm.


Hezsus said:


> Is it worth my time adding diodes/resistors to the f/n/r contactor?


I'm not sure what resistors you mean. Diodes are typically used to squelch the coil kickback and protect the switch controlling the coil. Those can be used if you're worried about your toggle switch.



Hezsus said:


> And is my voltage drop acceptable? aprox 10v drop, according to the controller under moderate to heavy load


Is that measured at the battery? What type of battery? At what current? But yep, 10V sounds excessive.


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## Hezsus (Oct 22, 2013)

major said:


> If the F/R contactors are both in the NO or both in the NC positions, the controller output is open circuit. So that should do no harm.
> 
> 
> I'm not sure what resistors you mean. Diodes are typically used to squelch the coil kickback and protect the switch controlling the coil. Those can be used if you're worried about your toggle switch.
> ...


I will probably install the diodes on the contactor since I have them, I'll leave out the resistors.

I was reading the voltage drop on the controller, I'll have to see exaclty where it was measured, the batteries are a group 31 size lead acid, brand new deep cycle 130ah and 900ca. I have 6, 12v. I noticed the worst voltage drops at full (or close charge and about 300-450a.. which I can only draw for just a second or 2, and when the batteries run lower (70 volts) They will drop low enough to hit the undervolt on the controller.

I have a digital volt guage ordered that I plan to run from the batteries (through the keyswitch) to give me a better indication

I purchased all the parts in a kit from electricmotosport.com and it came with 4 or 6ga wire, It was really nice looking wire so i decided to use it over the 2ga welding wire I have lots of, I ran out of the nice stuff though and have all 2ga from the controler to the motor. could the smaller wire be causing the voltage drop?

I can live with the drop when drawing 400+a but at 70v and very mild throttle it will drop to 60v.


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## Hezsus (Oct 22, 2013)

well I forgot to measure the voltage drop but I got the contactor wired properly, works much better.


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## dougingraham (Jul 26, 2011)

8 feet of 4 gauge wire has a resistance of about 0.002 ohms. At 450 amps there would be a voltage drop of 0.9 volts. There would be 405 watts wasted heat or about 51 watts per foot. If you do this very long the wire will get hot. That is not where your voltage drop is. With 6 gauge wire the voltage drop would be 1.4 volts (0.0031 ohms for the 8 feet) and the waste heat would be 640 watts or 80 watts per foot.

At 450 amps things will get hot if there is a problem. I would recommend going to a heavier gauge of wire if you find things are heating up.

Your voltage drop is probably just the lead acid batteries sagging.


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## Hezsus (Oct 22, 2013)

dougingraham said:


> 8 feet of 4 gauge wire has a resistance of about 0.002 ohms. At 450 amps there would be a voltage drop of 0.9 volts. There would be 405 watts wasted heat or about 51 watts per foot. If you do this very long the wire will get hot. That is not where your voltage drop is. With 6 gauge wire the voltage drop would be 1.4 volts (0.0031 ohms for the 8 feet) and the waste heat would be 640 watts or 80 watts per foot.
> 
> At 450 amps things will get hot if there is a problem. I would recommend going to a heavier gauge of wire if you find things are heating up.
> 
> Your voltage drop is probably just the lead acid batteries sagging.



Good to know, Thanks.. I have not had any heat issues since the stock fw/rev switch... it did not at all like the extra power. 
I have about 8' of 2ga wire and 6' of 6ga wire. i may switch the rest to 2ga, just to boost performance.. and I have the wire already.
I will blame the drop on the lead acid.. I hope to one day be able to afford something better.


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