# Parallel Contactors, Pre Charge Resistor, Disconnect



## athomas03 (Jul 13, 2011)

I have three questions regarding a racing project I'm doing with a golf cart. Running 96+ volts, possibly parallel PC680's with a main contactor that activates or closes to pull the + leg to controller.

1. If I parallel two EV200's does it double my amperage limits...ie 500 continuous becomes 1000 continuous.....as well as inrush limits? Parallel 680's would have 1360 PCA (5 seconds).......1/8 mile race....10 seconds or less. Are there other dangers to doing this......if one fails do they both fail??? 
2. Pre Charge Resistor - I have one that is oversized (with 72v I used 1k 10w it was real hot with parallel pack of PC925's).......4kohm 20 watt....any drawbacks to going overkill on the pre charge? I also have a 1800 ohm 25 watt. Voltage will be 96v to 120v......controller max. Its my understanding higher ohms is better protection for the controller and higher watts better proctects contactor.
3. Emergency disconnect.......when I bypassed, I placed this between M- and motor. But, now with no bypass if the main contactor fails, should I locate the disconnect on the + side between contactor and controller to stop current from the welded contactor?

Thanks for any help or suggestions.


----------



## frodus (Apr 12, 2008)

Kind of.....

The contactors will have slight differences in opening/closing speed, so EACH contactor must be able to take the fully loaded amps. If you open under load (say 1000A) and each contactor is theoretically carrying 500A, if one opens before the other, that full 1000A goes through that contactor momentarily. This will decrease the life of the contactor and can cause failure. So while you'd think it'd be 1000A total, that's only carry amps when closed. When opening and closing, you need to make sure it's done without any load, because you cannot guarantee that they'll open/close at the same time. 

Also, there could be slight differences in contact resistance, so there's nothing to guarantee that they will share current equally.

Best idea is to get one contactor that is designed for this application.



But.... Are you really doing 1000A continuous on the battery side in a Kart?


----------



## major (Apr 4, 2008)

athomas03 said:


> I have three questions regarding a racing project I'm doing with a golf cart. Running 96+ volts, possibly parallel PC680's with a main contactor that activates or closes to pull the + leg to controller.
> 
> 1. If I parallel two EV200's does it double my amperage limits...ie 500 continuous becomes 1000 continuous.....as well as inrush limits? Parallel 680's would have 1360 PCA (5 seconds).......1/8 mile race....10 seconds or less. Are there other dangers to doing this......if one fails do they both fail???
> 2. Pre Charge Resistor - I have one that is oversized (with 72v I used 1k 10w it was real hot with parallel pack of PC925's).......4kohm 20 watt....any drawbacks to going overkill on the pre charge? I also have a 1800 ohm 25 watt. Voltage will be 96v to 120v......controller max. Its my understanding higher ohms is better protection for the controller and higher watts better proctects contactor.
> ...


1.) A single EV200 will suffice. You are not running continuously. Look at the ratings information.

2.) Use a smaller Ohmic value for the precharge so it does its job quicker.

3.) Keep the E disconnect (contactor or otherwise) near the battery and definitely between the battery and controller to minimize arcing on disconnect.

What controller and motor are you running?


----------



## athomas03 (Jul 13, 2011)

major said:


> 1.) A single EV200 will suffice. You are not running continuously. Look at the ratings information.
> 
> 2.) Use a smaller Ohmic value for the precharge so it does its job quicker.
> 
> ...


Major, running a Logisystems 72-120 1200amp racing controller that was built by Jim before the company went under. These were built near the end just for racing purposes, not daily driver. I know I have no support should I fry it so I'm trying to protect as best I can. Most of the issues with these on the racing side have been from bypassing and boosting with the CEMF's, unless a large blocking diode has been placed (which I'm not aware of the part#). I am not going to bypass, the ramp up is very fast, but there have been some issues with parallel packs also causing some problems with the Logi (more so with parallel PC925's not 680's).

I know the EV200 has the coil economizer but I also placed a 6amp diode in between the small leads.......if this can hurt in anyway let me know, I was just going for overprotection once again. 

Motor is a reworked motor by Plumquick, double banded and setup for 72v drag racing.....but supposedly has been dyno'd to 10k rpm....I may find out with these higher voltages.


----------



## athomas03 (Jul 13, 2011)

frodus said:


> Kind of.....
> 
> The contactors will have slight differences in opening/closing speed, so EACH contactor must be able to take the fully loaded amps. If you open under load (say 1000A) and each contactor is theoretically carrying 500A, if one opens before the other, that full 1000A goes through that contactor momentarily. This will decrease the life of the contactor and can cause failure. So while you'd think it'd be 1000A total, that's only carry amps when closed. When opening and closing, you need to make sure it's done without any load, because you cannot guarantee that they'll open/close at the same time.
> 
> ...


Another racer is running series PC680's and his Zilla printout shows 1000 for 3 seconds from batts and too motor. So, I was getting a little nervous if a parallel pack doubles that for 3 seconds I will 2000 amps flowing. I was always under the impression the 680 would deliver 680 amps (PCA) for 5 seconds, but it delivers more (short circuit is 1800) for a short period. But is a race that is 10 seconds or less I only need the high amps early for low end torque and its okay if they drop down the track. Any suggestions are welcome as I am trying to learn. Thanks, Adam


----------



## TerryH (Jun 9, 2012)

athomas03 said:


> Another racer is running series PC680's and his Zilla printout shows 1000 for 3 seconds from batts and too motor. So, I was getting a little nervous if a parallel pack doubles that for 3 seconds I will 2000 amps flowing. I was always under the impression the 680 would deliver 680 amps (PCA) for 5 seconds, but it delivers more (short circuit is 1800) for a short period. But is a race that is 10 seconds or less I only need the high amps early for low end torque and its okay if they drop down the track. Any suggestions are welcome as I am trying to learn. Thanks, Adam


Other racer chiming in...LOL..

If nothing else, my DAQ file from the Zilla proves beyond a shadow of a doubt that at least on my drag cart, the 680's will flow well over 680 amps for at least 3 seconds. I saw peaks slightly over the 1000 amp limit of my Z1HV using the Fastrack program so I feel certian that parallel packs will flow well over the 1000 amps perhaps even 2000 for some period of time anyway. No clue what that period of time is but it would be interesting to find out.

And I do have a SB350 in the main positive cable from the pack to the controller for emergency purposes even though I doubt I would ever need it. It is nice to be able to disconnect everything to work on it though. I have a dead man switch on the steering wheel and on the deflector plate behind my head both connected to the key switch on the Z1.


----------



## athomas03 (Jul 13, 2011)

Controller










Motor


----------



## major (Apr 4, 2008)

athomas03 said:


> I know the EV200 has the coil economizer but I also placed a 6amp diode in between the small leads.......if this can hurt in anyway let me know, I was just going for overprotection once again.


Don't use the diode. It is not needed with the economizer and may interfere with proper operation like fast turn off.

And with out by-pass, the controller will limit the current regardless if you have stronger or paralleled batteries.


----------



## TerryH (Jun 9, 2012)

major said:


> Don't use the diode. It is not needed with the economizer and may interfere with proper operation like fast turn off.
> 
> And with out by-pass, the controller will limit the current regardless if you have stronger or paralleled batteries.


Stephen at Manzanita actually told me to run the diodes on my EV200's.  I have mine paralleled and I'm running a diode on each. Beats me but it seems to be working.


----------



## frodus (Apr 12, 2008)

He might have told you to use them with LEV200's, which have no economizer.

Don't use them with the EV200's. They're already built into the economizer.


----------



## TerryH (Jun 9, 2012)

frodus said:


> He might have told you to use them with LEV200's, which have no economizer.
> 
> Don't use them with the EV200's. They're already built into the economizer.


Quote from the email from Stephen Johnsen @ Manzinita...

"Since you have the diodes already you might as well put them over each of the 12V inputs to each contactor. Some people have said that the EV200 contactors do not need a snubber but I have seen a Hairball damaged by an EV200 without one and the cost of a snubber diode is MUCH less than the cost of a new Hairball and so easy to install."


----------



## major (Apr 4, 2008)

TerryH said:


> Quote from the email from Stephen Johnsen @ Manzinita...
> 
> "Since you have the diodes already you might as well put them over each of the 12V inputs to each contactor. Some people have said that the EV200 contactors do not need a snubber but I have seen a Hairball damaged by an EV200 without one and the cost of a snubber diode is MUCH less than the cost of a new Hairball and so easy to install."


I'd go with Stephen's recommendation due to the fact he is connected to Manzanita and should know what he's talking about. Maybe you should be using the LEV200 which doesn't have the economizer and then use special diode which is supplied with the Zilla.

Typically when using the EV200 (with economizer) it is standard procedure not to use an external diode on the coil.


----------



## TerryH (Jun 9, 2012)

major said:


> I'd go with Stephen's recommendation due to the fact he is connected to Manzanita and should know what he's talking about. Maybe you should be using the LEV200 which doesn't have the economizer and then use special diode which is supplied with the Zilla.
> 
> Typically when using the EV200 (with economizer) it is standard procedure not to use an external diode on the coil.


 
I assumed that I would not need the diodes with the EV200's as well but I asked the Zilla tech guys just to make sure. I was a bit surprised by Stephen's answer but I wanted to do what they recommended so I bought more of the same diodes that came with the Z1 so I could run one on each of the contactors.


----------



## frodus (Apr 12, 2008)

Go with Stephen's recommendation, he knows his Zilla stuff!

Any time you have a controller driving the contactor, I'd use an LEV200 series. Don't use anything with an economizer. Not sure how the Zilla drives the contactor, but it's wise to use a contactor with a Coil and Diode only, and no economizer.

You're just "doubling up" the diodes.


----------

