# Pre-Charge - How Long?



## Iboondock (Feb 16, 2010)

I have an Alltrax AXE4844 controller. 

Does anyone know how long it typically takes to charge the capacitors through the pre-charge resistor?


Thanks.


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## Jimdear2 (Oct 12, 2008)

Iboondock,

I measured my ALLTRAX 7245 and it takes about 15 to 20 seconds for the current to stop flowing through the resistor. 

This may vary on your model and will also depend on system voltage and the value of the precharge resistor you use.

To be sure for your set up, contact Alltrax and ask.

http://www.alltraxinc.com/index.html

They are very good about customer support. Also chech their library of documents and diagrams.


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## Iboondock (Feb 16, 2010)

Jimdear2 said:


> Iboondock,
> 
> I measured my ALLTRAX 7245 and it takes about 15 to 20 seconds for the current to stop flowing through the resistor.
> 
> This may vary on your model and will also depend on system voltage and the value of the precharge resistor you use.



Thanks for the quick reply. 

I didn't find anything in the Alltrax manuals, but haven't talked to anyone at Alltrax yet. I was hoping somebody one the forum knew off the top of their head.

That gives me a ball park for design anyway.

Thanks


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## Iboondock (Feb 16, 2010)

The response I received from Alltrax:

_
_
_"Without looking up the actual rate of the caps, the short answer is, in a blink. As soon s you connect, the caps will draw current. With a pcr, you don’t have to be concerned. In a manual contactor application (boat/cycle) closing the contactor with NO throttle or motor demand will charge them as well, but we prefer a separate switch for pcr in those cases. Thanks, Chuck_

_
_
_Customer Service Tech_
_Alltrax Inc"_


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## vpoppv (Jul 27, 2009)

Hmmmm, that is interesting. I used a 60w light bulb for my pre-charge resistor before my resistors came in the mail. It it took a few seconds for the light to dim- not exactly a blink. I've read people who have concluded that insufficient pre-charge time led to the demise of their controller. IMO, a 10 second pause is worth it.

At about 13 seconds into the video, you can just barely see the lightbulb light up and stay on for a few seconds:

http://www.youtube.com/watch?v=-w0oeUKesMQ


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