# Re: [EVDL] Switching the precharge resistor?



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

I'd say switch it on when you want the car to be active (like moving the key
to 'start'), and turn it off to save battery drain when you want the car
inactive (like moving the key away from 'run').

Why not leave the resistor permanently across the high side contactor and
stop the battery drain with a low side contactor? Kinda the same as
switching the resistor on to precharge, only now the switch is a contactor
instead of a small relay. Humm.. anyone else see a problem with doing this?
It could simplify my plans!

-Jon Glauser
http://jonglauser.blogspot.com
http://www.evalbum.com/555
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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

>
> I see a recent thread talking about how to power up the precharge
> resistor,
> my question is why would it ever need to be switched off? Does it draw
> that
> much power? My Alltrax diagram just shows it wired between the 2
> secondary
> contactor terminals, unswitched.

So you leave you controller powered up all the time? Don't you think
that's a little dangerous?
When controllers fail, they tend to fail full on. I.e. full power to the
motor.
Granted with the input power limited by the precharge resistor, all you'll
have available is the power stored in the caps, but that can still cause a
nasty surge.

Plus, the capacitors in your controller have a limited life span. One of
the things that effects this life span is how much time they spend with
voltage across them. Leaving the charged 24/7 can reduce their life span
significantly.

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

Where did you see that tidbit on the life of the caps is significantly affected by time on vs time off....

There is definitely a age curve to electrolytic capacitors but never noticed any affect for on vs off time. I have a pair of old controllers for my bandsaw (Belt drive DC speed controllers) Recently the controller died for bad filter caps after 5 years of no issues. Swapped in my spare (similar age and has not been powered on in those 5 years) and it died 5 weeks later as well for the same thing. I shouldn't have procrastinated so much and gotten replacement caps on order sooner . 

Later,
Peter

> Date: Fri, 20 Jun 2008 02:32:12 -0600
> From: [email protected]
> To: [email protected]
> Subject: Re: [EVDL] Switching the precharge resistor?
> 
> >
> > I see a recent thread talking about how to power up the precharge
> > resistor,
> > my question is why would it ever need to be switched off? Does it draw
> > that
> > much power? My Alltrax diagram just shows it wired between the 2
> > secondary
> > contactor terminals, unswitched.
> 
> So you leave you controller powered up all the time? Don't you think
> that's a little dangerous?
> When controllers fail, they tend to fail full on. I.e. full power to the
> motor.
> Granted with the input power limited by the precharge resistor, all you'll
> have available is the power stored in the caps, but that can still cause a
> nasty surge.
> 
> Plus, the capacitors in your controller have a limited life span. One of
> the things that effects this life span is how much time they spend with
> voltage across them. Leaving the charged 24/7 can reduce their life span
> significantly.
> 
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> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

I guess since the diagram didn't show any switching I didn't think it was
that important. Is the controller actually powered all the time, or just
the caps, since the power lead to the controller is still off? I assume I
could just use a simple switch in line to turn it on and off since it's a 48
volt low current circuit?




> Peter VanDerWal wrote:
> >
> > So you leave you controller powered up all the time? Don't you think
> > that's a little dangerous?
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

>
> I guess since the diagram didn't show any switching I didn't think it was
> that important. Is the controller actually powered all the time, or just
> the caps, since the power lead to the controller is still off? I assume I
> could just use a simple switch in line to turn it on and off since it's a
> 48
> volt low current circuit?

The power lead to the controller is ON!! it's being powered through the
resistor.

The only thing that is off is the KSI voltage which is just a logical
(yes/no) input to the processor.

Put the switch inline with just the resistor, (i.e. between the resistor
and it's connection to the relay) you don't want main current going
through the switch.

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*



> Jon Glauser wrote:
> > Why not leave the resistor permanently across the high side contactor and
> > stop the battery drain with a low side contactor? Kinda the same as
> > switching the resistor on to precharge, only now the switch is a contactor
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*



> Peter Shabino wrote:
> > There is definitely a age curve to electrolytic capacitors but never
> > noticed any effect for on vs off time. I have a pair of old
> > controllers for my bandsaw (Belt drive DC speed controllers) Recently
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

I routinely disconnect my 96 volt traction battery from the Curtis 1231C
when I park my EV in the garage any length of time.

Would I be better off leaving it connected through the pre-charge 
resistor, or building a circuit to maintain 75% on the 1231C?

My NG3 remains connected to the traction battery. Should I do the
same for it?

John in Sylmar, CA
www.evalbum.com/1749

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*



> > Jon Glauser wrote:
> >> Why not leave the resistor permanently across the high side contactor
> >> and
> >> stop the battery drain with a low side contactor? Kinda the same as
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

>From what I've read, there is no problem leaving electrolytics unpowered
for 6 months at a time. If it's been stored longer than that, it's best
tongradually apply voltage in steps to reform the insulation and reduce
problems with high leakage currents. Even with doing this, the leakage
currents will be high for the first couple days of operation, so avoid
pushing high power through it for the first few days (this will keep the
caps cooler)

At any rate, if storage is for less than 6 months and longer than a couple
weeks, follow the above advice about taking it easy for a couple days.
Other than that, I wouldn't worry about it.

> I routinely disconnect my 96 volt traction battery from the Curtis 1231C
> when I park my EV in the garage any length of time.
>
> Would I be better off leaving it connected through the pre-charge
> resistor, or building a circuit to maintain 75% on the 1231C?
>
> My NG3 remains connected to the traction battery. Should I do the
> same for it?
>
> John in Sylmar, CA
> www.evalbum.com/1749
>
> _______________________________________________
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> http://lists.sjsu.edu/mailman/listinfo/ev
>


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

That is how I ended up doing it. The low side contactor is turned on
with the keyswitch. The high side contactor is turned on when the
controller indicates the precharge is completed. The heater and dc/dc
are also connected at the same point.

If you only use one contactor, do not connect these things on the
controlled side of the contactor. You will be supplying them through
the precharge when the contactor is off and burn up the precharge. :-(
Putting a resistor on the precharge lead -like a 60 watt light
emitting resistor (lightbulb)- will prevent the burnout from this or
some other mistake and also make the caps life easier.)



> Jon Glauser <[email protected]> wrote:
> > I'd say switch it on when you want the car to be active (like moving the key
> > to 'start'), and turn it off to save battery drain when you want the car
> > inactive (like moving the key away from 'run').
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

Hello Storm,

No problem in having your low side contactor, which is normally call the 
safety contactors that turn off the battery power to the main main contactor 
and controller.

You must first turn on the battery contactors on first which I do with the 
ignition switch turn to the ON position. This power must first be apply to 
the line side of the main contactor first before the main contactor is 
activated, or some controllers will go in a error fault.

If I try to have all three contactors come on at the same time, they may be 
a difference in closing action, where the main contactor may close first and 
I get a error message, NO BATTERY POWER PRESENT AT MAIN CONTACTOR.

After I turn on the safety contactors with the IGNITION ON POSITION, I then 
turn on the main contactor with the IGNITION START POSITION which activates 
the main contactor and pre-charge circuit.

Roland

I then turn the ignition switch to the start position to activate the main 
contactor and pre charge. I can turn the ignition switch from ON to START 
in one motion

----- Original Message ----- 
From: "storm connors" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Sunday, June 22, 2008 5:51 AM
Subject: Re: [EVDL] Switching the precharge resistor?


> That is how I ended up doing it. The low side contactor is turned on
> with the keyswitch. The high side contactor is turned on when the
> controller indicates the precharge is completed. The heater and dc/dc
> are also connected at the same point.
>
> If you only use one contactor, do not connect these things on the
> controlled side of the contactor. You will be supplying them through
> the precharge when the contactor is off and burn up the precharge. :-(
> Putting a resistor on the precharge lead -like a 60 watt light
> emitting resistor (lightbulb)- will prevent the burnout from this or
> some other mistake and also make the caps life easier.)
>
> On Fri, Jun 20, 2008 at 11:33 AM, Jon Glauser <[email protected]> 


> > wrote:
> > > I'd say switch it on when you want the car to be active (like moving the
> > > key
> > > to 'start'), and turn it off to save battery drain when you want the car
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

How long should I wait to turn on the KSI after connecting the precharge
resistor? Is there a way to tell when the caps are charged?




> Peter VanDerWal wrote:
> >
> >
> > The power lead to the controller is ON!! it's being powered through the
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

I leave my precharge resistor always on in my truck as recommended by Alltr=
ax. I don't believe Peter is correct in his assesment, but he does have a =
reasonable track record on knowing what he is talking about, so I am going =
to send off an inquiry to the engineers at Logisystems and Alltrax since th=
ose are the two controllers I am currently using.
=

Here is my uneducated thoughts however. Their is no safety hazard. The ca=
ps don't hold enough energy to even move the vehicle a little... I have ac=
tually tried this on my motorcycle in the past. I have a 6 ohm precharge r=
esistor hooked across the main contactor through a momentary switch. When =
I engage the precharge resistor I can wait for the green light on the contr=
oller to light up without closing the main switch. Turning the throttle at=
this point does not move the motorcycle at all. The 10 amps of current av=
ailable through the resistor plus the energy stored in the capacitors does =
not provide enough power to even budge the thing.
=

As far as leaving voltage across the caps, I do not believe it effects thei=
r life span at all, but I could be wrong.
=

The only possible downside that I can see to this scenario is that it puts =
full pack voltage one more place that unsuspecting fingers might accidently=
touch.
=

damon



> Date: Sun, 22 Jun 2008 07:54:31 -0700> From: [email protected]> To: e=
[email protected]> Subject: Re: [EVDL] Switching the precharge resistor?> > =
> How long should I wait to turn on the KSI after connecting the precharge>=
resistor? Is there a way to tell when the caps are charged?> > > Peter Van=


> DerWal wrote:> > > > > > The power lead to the controller is ON!! it's bein=
> g powered through the> > resistor.> > > > The only thing that is off is the=
> KSI voltage which is just a logical> > (yes/no) input to the processor.> >=
> > > Put the switch inline with just the resistor, (i.e. between the resist=
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*



> damon henry wrote:
> > I leave my precharge resistor always on... There is no safety hazard.
> > The caps don't hold enough energy to even move the vehicle a
> > little... I have actually tried this on my motorcycle in the past.
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

In my Curtis Companion precharge controller, 
http://www.nimblemotorsports.com/web10/controllers.html
a micro measures the current and turns on the main
contactor only when the current stops flowing. If the
current never stops flowing, then there is a fault
somewhere, including a possible full-on broken
controller, such that when you then turn on the main
contactor, the car will launch full-speed ahead.
Jack



> --- AMPhibian <[email protected]> wrote:
> 
> >
> > How long should I wait to turn on the KSI after
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

I have been reading, slowly and carefully, this thread about precharge. 
You guys have a lot of finesse and understanding.
If I may be so bold as to ask, when you have it about resolved, would it 
be possible to attach a schematic or photo, so those of us who are less 
sophisticated might understand it and maybe even duplicate it?
Thanks in advance,
Bob





> Jack Murray wrote:
> > In my Curtis Companion precharge controller,
> > http://www.nimblemotorsports.com/web10/controllers.html
> > a micro measures the current and turns on the main
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

It's been a long time since I tried it on my motorcycle and my battery pack=
is currently torn apart so I can't run a quick test, but I am almost posit=
ive I have tried it in the past and was surprised that it would not even bu=
dge. However, my motorcycle only has a single gear ratio and I generally c=
an't start from a dead stop without seeing at least 100amps draw on the bat=
teries according to my emeter. =

=

It's actually a pretty easy experiment to run, especially on my motorcycle =
since I have the precharge resistor and main switch separated. I will prob=
ably try the same experiment on my truck now. All I need to do is manually=
enable the KSI without closing my main contactor and hop on the throttle t=
o see what/if lurch I get. No reason to theorize or estimate when emperica=
l knowledge is easy to come by  =

=

Now all I have to do is wait for my son to bring the truck home. =

=

It's great fun bringing the kids up on electric. They love it. Besides my=
17 year old son driving all around I have also been using my EV to teach m=
y 14 soon to be 15 year old daughter how to use a clutch. It is much easie=
r to teach her on a vehicle that doesn't throw a fit and die when she gets =
things wrong.
=

It sounds like in my case the caps should be happy since I am running a 120=
volt controller at 96 volts. I never have to worry about maxing the caps =
out so leaving them connected to pack voltage should not shorten their life=
span. I guess this is another case where the correct answer depends on the=
details of the situation.
=

damon
=

> From: [email protected]> To: [email protected]> Subject: Re: [EVDL] =
Switching the precharge resistor?> > damon henry wrote:> > I leave my prech=
arge resistor always on... There is no safety hazard.> > The caps don't hol=
d enough energy to even move the vehicle a> > little... I have actually tri=
ed this on my motorcycle in the past.> > I have a 6 ohm precharge resistor.=
..> > Are you sure, Damon? I can drive my EV with just the 0.5 amps provide=
d > by the precharge resistor. It has a 132v pack, Curtis 1231C controller,=
> and ADC 6.7" motor. The controller will happily step the 132v at 0.5 > a=
mps down to a couple volts at 20 amps, which is enough to run the > motor, =
and move the car (slowly) in 1st gear. If I wait for the > precharge to ful=
ly charge the controller's capacitors, I have a fraction > of a second at f=
ull power available, which will "chirp" the tires and > lurch the car forwa=
rd.> > > As far as leaving voltage across the caps, I do not believe it> > =
effects their life span at all, but I could be wrong.> > It depends on how =
close the voltage is to the capacitor's voltage > rating. Leaving 72v on a =
100v capacitor doesn't matter -- but leaving > 100 volts on it will!
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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

On Fri, 20 Jun 2008 02:32:12 -0600 (MDT), "Peter VanDerWal"


> <[email protected]> wrote:
> 
> >>
> >> I see a recent thread talking about how to power up the precharge
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

On Fri, 20 Jun 2008 06:41:25 -0600 (MDT), "Peter VanDerWal"


> <[email protected]> wrote:
> 
> >>
> >> I guess since the diagram didn't show any switching I didn't think it was
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*



> Lee Hart <[email protected]> wrote:
> 
> >Jon Glauser wrote:
> >> Why not leave the resistor permanently across the high side contactor and
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

On Sun, 22 Jun 2008 17:48:34 -0400, Robert Brown <[email protected]>


> wrote:
> 
> >I have been reading, slowly and carefully, this thread about precharge.
> >You guys have a lot of finesse and understanding.
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

Thank you for the detailed explanation. However the following quote is a bit
puzzling. You stated that the caps would likely last longer when
continuously powered which keeps them fully formed, yet you are switching
yours off.



> Neon John wrote:
> >
> > The only "problem" with the controller being powered all the time is that
> > it
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*

On Mon, 23 Jun 2008 06:15:25 -0700 (PDT), AMPhibian <[email protected]>


> wrote:
> 
> >
> >Thank you for the detailed explanation. However the following quote is a bit
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*



> Roland Wiench <[email protected]> wrote:
> 
> >
> > After I turn on the safety contactors with the IGNITION ON POSITION, I then
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Switching the precharge resistor?*



> "Zeke Yewdall" <[email protected]> wrote:
> 
> >On Sun, Jun 22, 2008 at 7:46 AM, Roland Wiench <[email protected]> wrote:
> >
> ...


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