# Precharge resistor and cycle analyst



## Yabert (Feb 7, 2010)

Hi

I have this kind of circuit and I have a problem: The cycle analyst don't turn OFF when I press the E-Stop.
Of course the problem is the resistor. Just enough juice pass by it and the cycle analyst screen stay ON. That cause the resistor to become hot.
I try another time with a 1,8K ohm resistor and it's better because the screen barely stay ON.
I try without resistor and the screen turn OFF after few second (because it stay powered by the energy from the capacitor in the Alltrax).

What could be a solution in this case?
*See post #6 for good shematic.*


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## kennybobby (Aug 10, 2012)

Maybe the E-stop was opened or closed while under a high current load and has welded the contacts together...?


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## Yabert (Feb 7, 2010)

No. In fact the e-stop work perfectly because without resistor across his contacts the cycle analyst Turn OFF.


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## major (Apr 4, 2008)

The resistor is across the contactor, not the e-stop.


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## kennybobby (Aug 10, 2012)

Is your schematic correct--when E-stop is pressed (opens the circuit) there will be no current thru the pre-charge resistor.


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## Yabert (Feb 7, 2010)

Fu*K! Sorry, I drew the schematic too fast.
There is no solenoid contactor and only a manual contactor (E-stop)
Hope it make sens now...


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## kennybobby (Aug 10, 2012)

merci, that makes sense now


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## Yabert (Feb 7, 2010)

So, is anyone know what kind of precharge resistor I could use?
It need to protect the the manual contactor when I close it and don't energize the cycle analyst when I open the contactor.
Idea?


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## kennybobby (Aug 10, 2012)

You really need some sort of ignition switch to control a power contactor so you can turn off the system--otherwise there is always power going to the motor controller thru the precharge circuit that will drain your pack.

then you need a separate on/off switch for the cycle analyst, or power it up from some internal power supply in the motor controller.


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## Yabert (Feb 7, 2010)

kennybobby said:


> You really need some sort of ignition switch to control a power contactor so you can turn off the system--otherwise there is always power going to the motor controller thru the precharge circuit that will drain your pack.


Despite if I use a really high value resistor? Let say 100K ohm? 1000K?

I'm still looking at a really simple schematic using only one manual contactor to energize everything. Is it possible?
My gold is to remove from a typical schematic the solenoid contactor and the key switch.


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## Yabert (Feb 7, 2010)

If I add a small and cheap solenoid relay to cut the current flow to the alltrax and cycle analyst, I'm good right?
But, with a 48v system, if I use a 470 ohm precharge resistor there will still remain 0,1A to energize the relay (48/470). Consequence the relay will stay closed.
So I need an higher value precharge resistor. Let say I put a 5k resistor, there will only have 0,001A available to energize the relay.
Base on a Omron G2R spec sheet, the relay should open with such a low power availble. Right?

But it will stil remain energize XX seconds with the energy store in the capacitor of the Alltrax.

Is anyone have a good idea for a proper way to stop everything with a single manual contactor?
Simply remove the precharge resistor is the easiest way, but this can cause failure of the contactor, right?


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## major (Apr 4, 2008)

Hi Yab,

Sometimes designing a minimal system is tough. Like I've done for 48V race kart with no 12V aboard. 

Don't like running without precharge. If contacts don't weld, controller caps eventually fail.

You're a resourceful guy. Suggest you think simple mechanism. Swivel bar keeping e-stop pushbutton off (depressed). Move swivel in order to pull pushbutton on; swivel also accuates microswitch which connects resistor across main contacts on e-stop. Use small Ohm R so precharge is very quick; like 80% before pushbutton can be pulled.

Hope you get the drift. Thinking spring loaded swivel handle covering pushbutton. Swivel latches out of the way so e-stop can be pushed off but swings back to cover pushbutton once it is in off position. 

Regards,

major


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## Yabert (Feb 7, 2010)

major said:


> Sometimes designing a minimal system is tough


Yeah, I will need to do something out of the box.
Thanks for the tips Major


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## Yabert (Feb 7, 2010)

I thought a bit more on the subject and to respect my mind to K.I.S.S. I end with this:

The Cycle analyst need 10 mA to be energised. A simple 10K ohm 1w resistor across the manual contactor will only allow 5 mA to flow. This will not be enought for the CA so it will turn off when the contactor is open.
Consequence, the resistor will burn a maximum of 1/4w (48v x 0,005A) continuously.
But I don't care because that imply it will drain down my battery in over 2 years (5 kWh / 1/4w = 20000 / 24h = 833 days).

Well, is all that make sens?
Let me know if I miss something.


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## major (Apr 4, 2008)

Yabert said:


> I thought a bit more on the subject and to respect my mind to K.I.S.S. I end with this:
> 
> The Cycle analyst need 10 mA to be energised. A simple 10K ohm 1w resistor across the manual contactor will only allow 5 mA to flow. This will not be enought for the CA so it will turn off when the contactor is open.
> Consequence, the resistor will burn a maximum of 1/4w (48v x 0,005A) continuously.
> ...


Yab,

If you use a high Ohm resistance like that, then with the load of the CA and controller cap leakage (including a bleed resistor which they likely have inside) will cause a voltage drop across the precharge resistor. So the caps in the controller will sit at a lower voltage than you might think. Easy to check. 

I think most would say you need like 80% precharge. You can probably live with less. Just increases arc on those contacts and shock (spike) to caps.

major


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## Duncan (Dec 8, 2008)

Hi Yabert
Just put a separate switch in the supply to the CA - just a normal switch

When you start up switch it on - if you drive off and notice that you haven't switched it on - just throw the switch


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## Yabert (Feb 7, 2010)

Duncan said:


> Just put a separate switch in the supply to the CA - just a normal switch


There is actually a separate switch to turn OFF the CA, but the differents drivers don't turn off this switch. They think to press the big/red manual switch, but not the small one. Consequence, the 470 ohm precharge resistor heat and drain the battery because the cycle analyst stay ON.

I think I will try few different value resistor and monitor the voltage as Major suggest... except if someone know how to calculate or have done similar test with a Cycle Analyst before.


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