# [EVDL] Question about pre-charge resistor value - Curtis 1231C



## EVDL List (Jul 27, 2007)

I used an oscilloscope to measure the time to charge my controller's input
caps using a few different resistor values. From this I calculated that the
input capacitance to be around 7,200 uF (Between B+ and B-). Does this mat=
ch
what others know about the Curtis 1231C 144V controller?

Now I'm trying to decide on the value of the pre-charge resistor to use. I=
've
got a Main contactor that comes on with the key, and my pre-charge resistor
will be installed across the Secondary contactor, which comes on when the
accelerator pedal is applied for the first time. So the pre-charge resistor
will start charging the caps when the key is turned on, but I won=92t push =
the
accelerator until my LED on the dashboard indicates that it's been charged =
to
90% or so. (I may add an interlock circuit so that the Secondary contactor
won=92t close until this condition is met.)

My problem is, if I use a 750 Ohm resistor as recommended in the Curtis man=
ual
then it would take over 20 seconds to charge to greater than 90% of the pack
voltage. (This is what my measurement showed, using a 12V supply for the te=
st,
since I don=92t have my batteries yet.) I don=92t want to wait this long b=
etween
turning on key and getting the car moving.

What's the minimum pre-charge resistor I should go with? I think it's a
trade-off of the current through the Main contactor when it first comes on =
vs.
the time I want to wait before pushing the accelerator pedal (and thereby
closing the Secondary contactor, and moving the car.)

Using a 100 Ohm pre-charge resistor with a 136 VDC battery pack would result
in a peak charging current of roughly 1.36A. This is the current that the
Main contactor would switch on. (I'm using a Kilovac EV200 with a coil
economizer). Does this seem reasonable or would I limit the life of the
contacts? If this is too high, what pre-charge resistor values are others
using? Are people using 750 Ohms and waiting 20 seconds for the pre-charge=
to
complete? Or using 750 Ohms and not waiting that long?

Thanks,
Chris
http://www.simonfamily.us/FocusEV/FocusEV.htm

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## EVDL List (Jul 27, 2007)

> Chris Simon wrote:
> > if I use a 750 Ohm resistor as recommended in the Curtis manual
> > then it would take over 20 seconds to charge to greater than 90% of the pack
> > voltage.
> ...


----------



## EVDL List (Jul 27, 2007)

When I built my Vee-Dub, I queried EA about using a pre-charge resistor (or
light) with my Curtis 1231B, (96-volt) as it was not shown in the wiring
diagram provided. They told me I didn't need one ... So I haven't. One year
later: Am I missing something?

Roger Daisley
Pullman, WA
www.96-volt.com

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## EVDL List (Jul 27, 2007)

Same here Roger. Every time you hit the go pedal the secondary contactor 
pulls in and the caps get hit with a jolt, but EA said a resistor is not 
needed. I have 3000 miles on the curtis with no problems. Al

----- Original Message ----- 
From: "Roger Daisley" <[email protected]>
To: "'Electric Vehicle Discussion List'" <[email protected]>
Sent: Wednesday, July 09, 2008 10:43 AM
Subject: Re: [EVDL] Question about pre-charge resistor value - Curtis 1231C


> When I built my Vee-Dub, I queried EA about using a pre-charge resistor 
> (or
> light) with my Curtis 1231B, (96-volt) as it was not shown in the wiring
> diagram provided. They told me I didn't need one ... So I haven't. One 
> year
> later: Am I missing something?
>
> Roger Daisley
> Pullman, WA
> www.96-volt.com
>
> _______________________________________________
> For general EVDL support, see http://evdl.org/help/
> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev
> 

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## EVDL List (Jul 27, 2007)

> Roger Daisley wrote:
> > When I built my Vee-Dub, I queried EA about using a pre-charge resistor (or
> > light) with my Curtis 1231B, (96-volt) as it was not shown in the wiring
> > diagram provided. They told me I didn't need one ... So I haven't. One year
> ...


----------



## EVDL List (Jul 27, 2007)

Ahh but Lee, would this only be the first time everyday or would this be
every time you press on the pedal to close the contactor? Wouldn't the
charge try to stay in the caps when the contactor opens? If the caps were
really good caps then the charge might even be there tomorrow. Not that I am
on the "no resistor" side of this as I am not. The pre charge resistor is
important for exactly the reasons you state. I am just saying that if you
get past that first time event you might be ok for a long long time.

Mark Grasser
Eliot, ME

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Lee Hart
Sent: Wednesday, July 09, 2008 4:17 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Question about pre-charge resistor value - Curtis 1231C



> Roger Daisley wrote:
> > When I built my Vee-Dub, I queried EA about using a pre-charge resistor
> (or
> > light) with my Curtis 1231B, (96-volt) as it was not shown in the wiring
> ...


----------



## EVDL List (Jul 27, 2007)

IIRC, the Cursit 1221 needs a precharge resistor, the 1231C does not.

Joseph H. Strubhar

Web: www.gremcoinc.com

E-mail: [email protected]
----- Original Message ----- 
From: "Al" <[email protected]>
To: <[email protected]>; "Electric Vehicle Discussion List" 
<[email protected]>
Sent: Wednesday, July 09, 2008 9:47 AM
Subject: Re: [EVDL] Question about pre-charge resistor value - Curtis 1231C


> Same here Roger. Every time you hit the go pedal the secondary contactor
> pulls in and the caps get hit with a jolt, but EA said a resistor is not
> needed. I have 3000 miles on the curtis with no problems. Al
>
> ----- Original Message ----- 
> From: "Roger Daisley" <[email protected]>
> To: "'Electric Vehicle Discussion List'" <[email protected]>
> Sent: Wednesday, July 09, 2008 10:43 AM
> Subject: Re: [EVDL] Question about pre-charge resistor value - Curtis 
> 1231C
>
>
>> When I built my Vee-Dub, I queried EA about using a pre-charge resistor
>> (or
>> light) with my Curtis 1231B, (96-volt) as it was not shown in the wiring
>> diagram provided. They told me I didn't need one ... So I haven't. One
>> year
>> later: Am I missing something?
>>
>> Roger Daisley
>> Pullman, WA
>> www.96-volt.com
>>
>> _______________________________________________
>> For general EVDL support, see http://evdl.org/help/
>> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev
>>
>
> _______________________________________________
> For general EVDL support, see http://evdl.org/help/
> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev
>
>
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> Version: 8.0.138 / Virus Database: 270.4.7/1543 - Release Date: 7/9/2008 
> 6:32 PM
>
>
> 

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## EVDL List (Jul 27, 2007)

Mark,

While I was measuring the charge time of the Curtis input capacitors I also
had a chance to watch them discharge. I didn't make a precise measurement but
they actually came down significantly in about 30 seconds - certainly a
minute. And this was with nothing else to load them. I'm considering adding
a ciruit to detect the pre-charge status and that will introduce a slight
discharge current that will speed their discharge.

So for many of the EVs out there (which have a contactor that opens when the
accelerator pedal is relaeased) the contactor and Curtis input caps will be
stressed at every stoplight or after coasting for a while. A pre-charge
resistor (or light bulb would be able to hold the voltage without
dissipating much power after the initial charging.

Chris

> Mark Grasser said:
>
> Ahh but Lee, would this only be the first time everyday or would this be
> every time you press on the pedal to close the contactor? Wouldn't the
> charge try to stay in the caps when the contactor opens? If the caps were
> really good caps then the charge might even be there tomorrow. Not that I am
> on the "no resistor" side of this as I am not. The pre charge resistor is
> important for exactly the reasons you state. I am just saying that if you
> get past that first time event you might be ok for a long long time.

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## EVDL List (Jul 27, 2007)

My EV w/ 1800 miles on a Curtis 1221B and no resistor has significant arc 
damage on the contactor.

I'm putting in a 1221C AND a resistor at the moment..just haven't calculated 
the value yet...

Jack





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## EVDL List (Jul 27, 2007)

About three weeks back on the EVDL, trying to get caught up...

Anyways, have a VoltsRabbit with about 30K on the Curtis 1231C
(replaced the 1221B that blew up back in 1995 after one year). I
have no precharge resistor, wired standard VoltsRabbit, and the
contactor is controlled via the accelerator pedal. I have in the
past noticed some pitting on the Albright contacts. But it all
works, and has for 12 years. Someday I'll add a precharge
resistor, but it's down a ways on that long, long list...

Chuck

----- Original Message ----- 
From: "Mark Grasser" <[email protected]>
To: "'Electric Vehicle Discussion List'" <[email protected]>
Sent: Wednesday, July 09, 2008 1:17 PM
Subject: Re: [EVDL] Question about pre-charge resistor value -
Curtis 1231C


> Ahh but Lee, would this only be the first time everyday or
would this be
> every time you press on the pedal to close the contactor?
Wouldn't the
> charge try to stay in the caps when the contactor opens? If the
caps were
> really good caps then the charge might even be there tomorrow.
Not that I am
> on the "no resistor" side of this as I am not. The pre charge
resistor is
> important for exactly the reasons you state. I am just saying
that if you
> get past that first time event you might be ok for a long long
time.
>
> Mark Grasser
> Eliot, ME
>
> -----Original Message-----
> From: [email protected]
[mailto:[email protected]] On Behalf
> Of Lee Hart
> Sent: Wednesday, July 09, 2008 4:17 PM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Question about pre-charge resistor value -
Curtis 1231C
>


> > Roger Daisley wrote:
> > > When I built my Vee-Dub, I queried EA about using a
> pre-charge resistor
> > (or
> ...


----------



## EVDL List (Jul 27, 2007)

Just curious why you would ignore Curtis
recommendation
to add at least the mininum under $10 part?
Jack



> --- Chuck Hursch <[email protected]> wrote:
> 
> > About three weeks back on the EVDL, trying to get
> > caught up...
> ...


----------



## EVDL List (Jul 27, 2007)

Back when I built the car in 1994, I did not even know about
precharge resistors, and I did not have a Curtis manual. I built
the car pretty much according to the ElectroAutomotive
installation manual. The installation manual (at that time at
least) had no mention of a precharge resistor. The person who
was helping me build the car I don't recall having a precharge
resistor on any of his EVs running Curtii.

When I get to it, I'll gather up all the precharge methods that I
have read about on this list, and decide which one I want to do.
When I make changes to the car, it's gotta work everytime - no
failures in the middle of the night when I leave work (in no less
a driving rainstorm). The only failure the car has had that was
a show stopper was the 1221B kabaam back in 1995. So, it works
the way it is right now.

That said, with the 1231C voltage range being 96-144V, you can
probably get away without a precharge resistor at 96V (I
certainly have). At 144V, the inrush current on those caps might
be great enough to cause a problem after awhile.

I doubt the 1221B died because of no precharge. It died because
of overheating and being run at or near its motor current limit
on my apt. hill too many times. When the 1221B died, Mike Brown
@ ElectroAutomotive kindly gave me a loaner 1221B until we got
the scene straightened out. The loaner controller within a few
days also started having problems on my hill (namely motor
voltage cutback), and probably would've blown up too after
awhile. The 1231C has been happy as a clam, and also within the
last few years, if I have no car on my tail starting up the hill,
I'll keep the battery current at 250A or a little less and just
let the car slow down and crawl, mainly for the health of the
US125 6V flooded batteries.

Chuck

----- Original Message ----- 
From: "Jack Murray" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Monday, July 28, 2008 12:28 PM
Subject: Re: [EVDL] Question about pre-charge resistor value -
Curtis 1231C


> Just curious why you would ignore Curtis
> recommendation
> to add at least the mininum under $10 part?
> Jack
>


> > --- Chuck Hursch <[email protected]> wrote:
> >
> > > About three weeks back on the EVDL, trying to get
> > > caught up...
> ...


----------



## EVDL List (Jul 27, 2007)

i was never told about the precharge either. ran my truck for 13 months with 
out it until the 1231c popped. it popped againa after about 13 months. after 
the second rebuild is when i found out about the need for a precharge 
resistor from flight systems.
there were no circuit problems found. i do know that rebuilt curtis' may use 
rebuilt parts that may be stressed from previous failures.

thanks
lee

----- Original Message ----- 
From: "Chuck Hursch" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Thursday, July 31, 2008 3:09 PM
Subject: Re: [EVDL] Question about pre-charge resistor value - Curtis 1231C


> Back when I built the car in 1994, I did not even know about
> precharge resistors, and I did not have a Curtis manual. I built
> the car pretty much according to the ElectroAutomotive
> installation manual. The installation manual (at that time at
> least) had no mention of a precharge resistor. The person who
> was helping me build the car I don't recall having a precharge
> resistor on any of his EVs running Curtii.
>
> When I get to it, I'll gather up all the precharge methods that I
> have read about on this list, and decide which one I want to do.
> When I make changes to the car, it's gotta work everytime - no
> failures in the middle of the night when I leave work (in no less
> a driving rainstorm). The only failure the car has had that was
> a show stopper was the 1221B kabaam back in 1995. So, it works
> the way it is right now.
>
> That said, with the 1231C voltage range being 96-144V, you can
> probably get away without a precharge resistor at 96V (I
> certainly have). At 144V, the inrush current on those caps might
> be great enough to cause a problem after awhile.
>
> I doubt the 1221B died because of no precharge. It died because
> of overheating and being run at or near its motor current limit
> on my apt. hill too many times. When the 1221B died, Mike Brown
> @ ElectroAutomotive kindly gave me a loaner 1221B until we got
> the scene straightened out. The loaner controller within a few
> days also started having problems on my hill (namely motor
> voltage cutback), and probably would've blown up too after
> awhile. The 1231C has been happy as a clam, and also within the
> last few years, if I have no car on my tail starting up the hill,
> I'll keep the battery current at 250A or a little less and just
> let the car slow down and crawl, mainly for the health of the
> US125 6V flooded batteries.
>
> Chuck
>
> ----- Original Message ----- 
> From: "Jack Murray" <[email protected]>
> To: "Electric Vehicle Discussion List" <[email protected]>
> Sent: Monday, July 28, 2008 12:28 PM
> Subject: Re: [EVDL] Question about pre-charge resistor value -
> Curtis 1231C
>
>
>> Just curious why you would ignore Curtis
>> recommendation
>> to add at least the mininum under $10 part?
>> Jack
>>


> >> --- Chuck Hursch <[email protected]> wrote:
> >>
> >> > About three weeks back on the EVDL, trying to get
> >> > caught up...
> ...


----------



## EVDL List (Jul 27, 2007)

Do you leave the light bulb connected all the time you are using the car?
I used the bulb, but I only precharged before driving, then I disconnect it.



> Lee Hart <[email protected]> wrote:
> 
> > Chris Simon wrote:
> > > if I use a 750 Ohm resistor as recommended in the Curtis manual
> ...


----------



## EVDL List (Jul 27, 2007)

> m gol wrote:
> > Do you leave the light bulb connected all the time you are using the car?
> > I used the bulb, but I only precharged before driving, then I disconnect it.
> 
> ...


----------



## EVDL List (Jul 27, 2007)

> m gol wrote:
> > Do you leave the light bulb connected all the time you are using the car?
> > I used the bulb, but I only precharged before driving, then I disconnect it.
> 
> ...


----------



## EVDL List (Jul 27, 2007)

If you are using 2 contactors, you can eliminate the relay. Precharge
connected to positive pack lead through the lightbulb. Turning on the
key closes the negative contactor which connects the controller to the
negative. With the Raptor, precharge completion turns on the positive
contactor.



> Lee Hart <[email protected]> wrote:
> > m gol wrote:
> >> Do you leave the light bulb connected all the time you are using the car?
> >> I used the bulb, but I only precharged before driving, then I disconnect it.
> ...


----------



## EVDL List (Jul 27, 2007)

Yes - you can do it that way, but now you've lost one of the main advantages of having a second ( negative side) contactor, in that the battery pack is no longer isolated from the rest of the vehicle ( in particular the motor, which can easily have some leakage to chassis ground) when charging.


Phil Marino

> Date: Sat, 2 Aug 2008 15:53:31 -0400
> From: [email protected]
> To: [email protected]
> Subject: Re: [EVDL] Question about pre-charge resistor value - Curtis 1231C
> 
> If you are using 2 contactors, you can eliminate the relay. Precharge
> connected to positive pack lead through the lightbulb. Turning on the
> key closes the negative contactor which connects the controller to the
> negative. With the Raptor, precharge completion turns on the positive
> contactor.
> 
>


> Lee Hart <[email protected]> wrote:
> > > m gol wrote:
> > >> Do you leave the light bulb connected all the time you are using the car?
> > >> I used the bulb, but I only precharged before driving, then I disconnect it.
> ...


----------



## EVDL List (Jul 27, 2007)

Thanks Phil. I hadn't considered that angle.



> Phil Marino <[email protected]> wrote:
> >
> > Yes - you can do it that way, but now you've lost one of the main advantages of having a second ( negative side) contactor, in that the battery pack is no longer isolated from the rest of the vehicle ( in particular the motor, which can easily have some leakage to chassis ground) when charging.
> >
> ...


----------



## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> > m gol wrote:
> > > Do you leave the light bulb connected all the time you are
> using the car?
> ...


----------



## EVDL List (Jul 27, 2007)

Hi, Chuck

I'm using a ceiling fan light bulb - 40 watts - that I got at Home Depot. The package claims " vibration resistant". It fits a candelabra base ( like 5 watt Christmas bulbs) and it's pretty small - about 1 inch max diameter and 3 inches long. I got a small ceramic socket for it at my local hardware store. 

I've got a conventional resistor ( 800 ohm 25 watts) in parallel, in case the bulb breaks. The precharge time with the resistor would be kind of long, but better than nothing.

Another option would be to use two ( or more) of these bulbs in parallel.

I measured the bulb current at different voltages: 0.32 amps at 120V, 0.23 amps at 60 volts, and 0.12 amps at 10 volts. AND, the cold filament resistance is 27 ohms, so my startup surge would be about 4 amps with my pack. Not too bad. 

The precharge time ( to 6 volts across the main contactor) is 4 or 5 seconds with a 104 volt pack and a Curtis 1221C.

Phil

> From: [email protected]
> To: [email protected]
> Date: Tue, 5 Aug 2008 14:49:19 -0700
> Subject: Re: [EVDL] Question about pre-charge resistor value - Curtis 1231C
> 


> > Lee Hart wrote:
> > > m gol wrote:
> > > > Do you leave the light bulb connected all the time you are
> > using the car?
> ...


----------



## EVDL List (Jul 27, 2007)

> Phil Marino <[email protected]> wrote:
> 
> >
> >Hi, Chuck
> ...


----------



## EVDL List (Jul 27, 2007)

Would someone look at page 4 of this document
http://www.canev.com/PressRelease/BornToBeWired_HPIssue122.pdf and
tell me where in the wiring diagram the precharge resistor and relay
would go. Does it basically "short" across the main contactor? Thank
you.

-- 
David D. Nelson

http://evalbum.com/1328

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## EVDL List (Jul 27, 2007)

> David Nelson wrote:
> 
> > Would someone look at page 4 of this document
> > http://www.canev.com/PressRelease/BornToBeWired_HPIssue122.pdf and
> ...


----------



## EVDL List (Jul 27, 2007)

> Chuck Hursch wrote:
> > The more I think about it, the more I like the light bulb idea.
> > Only two problems: breakage and size. What do you use to
> > protect the bulb - a cage like a drop light, or is it naked?
> ...


----------



## EVDL List (Jul 27, 2007)

Thank you, Doug. That is one more thing I won't have to worry about.



> Doug Weathers <[email protected]> wrote:
> >
> > On Aug 6, 2008, at 10:19 AM, David Nelson wrote:
> >
> ...


----------



## EVDL List (Jul 27, 2007)

Ok, thanks Phil, Neon John, and Lee for the info. It's those
details such as where to get a light bulb that can survive under
the hood, that if I don't know 'em, make the project go on the
back burner for another day. Now I've got some ideas 

Presumably, with those inrush currents, it's not only the
controller's caps, but the contacts in the main contactor, that
get hammered. I know there is some pitting on my contacts. I
suppose eventually the resistance could get high enough that
you'd damage the contactor with heat. Another good reason for a
precharge circuit.

Lee, it certainly looks like in that photo that you had to
shoehorn that pack in at an angle. Am I just seeing things or is
that actually the case?

Thanks,
Chuck

----- Original Message ----- 
From: "Lee Hart" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Wednesday, August 06, 2008 8:37 PM
Subject: Re: [EVDL] Question about pre-charge resistor value -
Curtis 1231C




> > Chuck Hursch wrote:
> > > The more I think about it, the more I like the light bulb
> idea.
> > > Only two problems: breakage and size. What do you use to
> ...


----------



## EVDL List (Jul 27, 2007)

> Chuck Hursch wrote:
> > Lee, it certainly looks like in that photo that you had to
> > shoehorn that pack in at an angle. Am I just seeing things or is
> > that actually the case?
> ...


----------



## EVDL List (Jul 27, 2007)

RE: /"It's actually a 130v 75w "black light" bulb, which is coated with 
a deeppurple plastic-like coating that blocks almost all the visible 
light.The plastic also (I hope) makes it more break-resistant. If I were 
to replace it, I'd use a garage door bulb or "drop light" bulb, which 
are specifically advertised as being more resistant to shock and 
vibration."/

I like the light bulb idea! If you are trying minimize shards of broken 
glass, you can purchase at any appliance dealer from Lowes on up a light 
bulb that is "food safe" - coated with a laltex or some sort of flexible 
coating that contains [pieces of glass if broken - thus keeping them out 
of your soup. They are also vibration proofed (if that is possible) to 
be used in the ventilation hood over the family cook stove.
Would serve the same purpose here.
Bob





> Lee Hart wrote:
> > Chuck Hursch wrote:
> >
> >> The more I think about it, the more I like the light bulb idea.
> ...


----------

