Switching the precharge resistor?

[AMPhibian]

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.
http://www.alltraxinc.com/files/Doc100-045-A_DWG-AXE-No-Reverse-wire-dia.pdf
http://www.alltraxinc.com/files/Doc100-045-A_DWG-AXE-No-Reverse-wire-dia.pdf

[Jon Glauser]

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

[Lee Hart]

Post by Jon Glauser
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!

That is indeed the best plan.

[Peter VanDerWal]

Post by Lee Hart

Post by Jon Glauser
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!

That is indeed the best plan.

The only down side is the expense of having two main contactors, and the
(minor) hassle of having to engage them in sequence.

[Neon John]

Post by Lee Hart

Post by Jon Glauser
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!

That is indeed the best plan.

Just to quibble, adding a low side contactor is adding another relatively high
failure-rate component to the mix in an attempt to solve a non-existent
problem.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
If stupidity hurt then they'd be putting morphine in the water supply.

[storm connors]

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.)

Post by Jon Glauser
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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[Roland Wiench]

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" <stormconnors-***@public.gmane.org>
To: "Electric Vehicle Discussion List" <ev-UWgVIey+***@public.gmane.org>
Sent: Sunday, June 22, 2008 5:51 AM
Subject: Re: [EVDL] Switching the precharge resistor?

Post by storm connors
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.)

Post by Jon Glauser
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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http://stormselectric.blogspot.com/
Storm
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[Zeke Yewdall]

Post by Roland Wiench
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.
This is sort of what I was thinking of -- so you have to consciously

"start" the car before driving off, just like an ICE, instead of just
turning it on.

[Neon John]

Post by Zeke Yewdall

Post by Roland Wiench
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.
This is sort of what I was thinking of -- so you have to consciously

"start" the car before driving off, just like an ICE, instead of just
turning it on.

No, I still just turn it on. There is a time delay module that closes the
main contactor about 2 seconds after the pre-charge relay. I hear a "click"
<tick> <toc> "Clack" and I'm live.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
I like you ... you remind me of me when I was young and stupid.

[Peter VanDerWal]

Post by AMPhibian
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.

[Peter Shabino]

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

Post by AMPhibian
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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[Lee Hart]

Post by Peter Shabino
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
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.

Electrolytic capacitors do have relatively short life expectancies. Look
at their data sheets; 1000 hours at full rated voltage and temperature
is typical. That's only a little over 1 month!

Now, these numbers are worst case; the life is *strongly* affected by
temperature and voltage. Temperature has the greatest effect. The heat
can either come from the ambient temperature (parked outside in Arizona
in the summer) or from ripple current (from charging or driving). The
capacitor life roughly *halves* for every 10 deg.C increase in temperature!

The voltage effect is more complicated. Capacitors last the longest at
about 75% of rated voltage. Going above this shortens life by putting
more stress on the insulation. It's maybe half the life at 100% of rated
voltage, and falls really fast as you go still higher.

But going down in voltage shortens life, too. It won't fail from voltage
breakdown; it will fail from issues like higher leakage current, ESR,
capacitance change, or a reduction in its voltage rating. At zero
voltage (like when you let the capacitor sit unused for years), the
capacitance, leakage, and voltage rating will get so bad that the
capacitor is likely to fail very soon after being put back in service!

To combat this, it is recommended that you gradually apply voltage to
things with old capacitors to let them "reform" their insulation before
putting the device is regular service.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

[JS]

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

[Peter VanDerWal]

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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[AMPhibian]

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?

Post by Peter VanDerWal
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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[Peter VanDerWal]

Post by AMPhibian
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.

[AMPhibian]

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?

Post by Peter VanDerWal
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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[damon henry]

I leave my precharge resistor always on in my truck as recommended by Alltrax. 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 those are the two controllers I am currently using.

Here is my uneducated thoughts however. Their 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. I have a 6 ohm precharge resistor hooked across the main contactor through a momentary switch. When I engage the precharge resistor I can wait for the green light on the controller 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 available 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 their 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
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[Lee Hart]

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.
I have a 6 ohm precharge resistor...

Are you sure, Damon? I can drive my EV with just the 0.5 amps provided
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
amps 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 fully charge the controller's capacitors, I have a fraction
of a second at full power available, which will "chirp" the tires and
lurch the car forward.

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!

[damon henry]

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 positive I have tried it in the past and was surprised that it would not even budge. However, my motorcycle only has a single gear ratio and I generally can't start from a dead stop without seeing at least 100amps draw on the batteries 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 probably 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 to see what/if lurch I get. No reason to theorize or estimate when emperical 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 my 14 soon to be 15 year old daughter how to use a clutch. It is much easier 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 lifespan. I guess this is another case where the correct answer depends on the details of the situation.

damon
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[Jack Murray]

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

Post by AMPhibian
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?

Post by Peter VanDerWal
The power lead to the controller is ON!! it's

being powered through the

Post by Peter VanDerWal
resistor.
The only thing that is off is the KSI voltage

which is just a logical

Post by Peter VanDerWal
(yes/no) input to the processor.
Put the switch inline with just the resistor,

(i.e. between the resistor

Post by Peter VanDerWal
and it's connection to the relay) you don't want

main current going

Post by Peter VanDerWal
through the switch.
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Post by AMPhibian
Sent from the Electric Vehicle Discussion List
mailing list archive at Nabble.com.
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[Robert Brown]

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

Post by Jack Murray
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

Post by AMPhibian
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?

Post by Peter VanDerWal
The power lead to the controller is ON!! it's

being powered through the

Post by Peter VanDerWal
resistor.
The only thing that is off is the KSI voltage

which is just a logical

Post by Peter VanDerWal
(yes/no) input to the processor.
Put the switch inline with just the resistor,

(i.e. between the resistor

Post by Peter VanDerWal
and it's connection to the relay) you don't want

main current going

Post by Peter VanDerWal
through the switch.
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Post by AMPhibian
Sent from the Electric Vehicle Discussion List
mailing list archive at Nabble.com.
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[Neon John]

Post by Robert Brown
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,

The guy who started this thread posted two links to Alltrax schematics.

John

--
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See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
No one can be right all of the time, but it helps to be right most of the time. -Robert Half

[Neon John]

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

Post by Peter VanDerWal

Post by AMPhibian
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.

Get a grip, Peter. His Alltrax is powered up by a 1k resistor if it is the 72
volt model. That's 72/1000 = 0.072 amps max. Do ya think that'll launch his
car through the garage wall?

John

--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
If stupidity hurt then they'd be putting morphine in the water supply.

[Neon John]

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

Post by Peter VanDerWal

Post by AMPhibian
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?

No. None. Nada.

Post by Peter VanDerWal
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.

No it can't, not with an Alltrax.

A 72 volt Alltrax stores insufficient energy to even move a CitiCar. The best
it can do is cause a little vibration in the frame. The wheels barely move
even with the car on jacks.

The 450 amp, 48 volt Alltrax in my GoBig stores just enough energy to take up
the slack in the chain. Or power the 50 watt halogen headlight (through a
48/12 volt converter) for less than a second after the contactor opens if I
leave the light on.

Post by Peter VanDerWal
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.

It'll actually probably extend their lives because it keeps them fully formed.
Ripple current and heat are what kills electrolytic caps. Neither is present
when the vehicle is stationary and the controller is powered only by the
pre-charge resistor.

This is way beyond an academic consideration, as if they fail, they'll fail in
service LONG before they'll fail just sitting there with a charge on 'em.

To answer the OP's question (it'd be nice to have a name to go with that
handle!), the only concern is that the resistor could very very slowly run
down your main pack. I can't conveniently find the standby current draw of an
AXE but it has to be small.

At 72 volts with the 1000 ohm resistor as specified, the MAX that could be
drawn with the AXE's terminals shorted is 72^2/1000 ohms = 5.2 watts. Probably
no more than a watt in practice, since the AXE can be powered up for
programming with 2 9 volt batteries in series (72 volt) or one 9 volt battery
for the rest. And since the pre-charge resistor gets barely warm when the car
is off.

If you have 72 volts' worth of 220 amp-hour golf cart batteries then you have
15.8kWh of energy storage. If the controller draws a watt on standby through
the pre-charge resistor then it would take 15,800 hours to run down your pack.
Pretty much a non-issue. If you leave your car plugged in on float when
you're not driving it then it really is a non-issue.

The only "problem" with the controller being powered all the time is that it
drains off the small "surface charge" that freshly charged batteries hold for
some time. That surface charge will give you an initial kick in the butt if
you floor the accelerator right out of the driveway. I enjoyed that kick in
the butt so I put a relay in series with the pre-charge resistor that
energized the pre-charge a couple of seconds before energizing the main
contactor. A very minor but pleasurable effect preserved. :-)


John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Save the whales, collect the whole set!

[AMPhibian]

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.

Post by Neon John
The only "problem" with the controller being powered all the time is that it
drains off the small "surface charge" that freshly charged batteries hold for
some time. That surface charge will give you an initial kick in the butt if
you floor the accelerator right out of the driveway. I enjoyed that kick in
the butt so I put a relay in series with the pre-charge resistor that
energized the pre-charge a couple of seconds before energizing the main
contactor. A very minor but pleasurable effect preserved. :-)
It'll actually probably extend their lives because it keeps them fully formed.
Ripple current and heat are what kills electrolytic caps. Neither is present
when the vehicle is stationary and the controller is powered only by the
pre-charge resistor.

Could you clarify?

John

[Neon John]

Post by AMPhibian
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.
Could you clarify?

Sure.

I'm speaking of the surface charge on the BATTERIES and not the caps. For
awhile after a battery is taken off the charger, the battery will show a
higher than "normal" voltage. This is referred to as "surface charge" because
it resides on the surface of the plates and not down in the active materials.

If I pull my vehicle off the charger and fairly soon afterward nail the
throttle, I get more power and more acceleration - the kick in the butt - than
I would if the fully charged batteries sat for awhile. The pre-charge
resistor bleeds down this surface charge a lot faster than would natural
processes. Therefore I open the precharge circuit so that there is no load at
all on the batteries.

It's a minor little enjoyment that cost me nothing since the relay and the
time delay relay came out of my junk box. I'd not bother if I had to buy
either.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
No one can be right all of the time but I'm getting close.