Precharge circuit preliminary test (was: Precharge alternatives)

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Precharge circuit preliminary test (was: Precharge alternatives)

eric@zyxod.com


[Cross-posted to evtech]

I tried the vacuum tube method mentioned below last night.

Charging a 6000uF cap bank from 0v to 30V with a 35V power supply took
18 seconds using both diodes in a 12x4 tube.  Ten seconds elapsed before
there was any change in the capacitor voltage, probably because of the
filament warm-up time.

When I get a chance to bust out my super-dirty power supply (variac,
rectifier, capacitor), I'll test it at 150VDC, and post the results.

I bought two of the tubes, and I expect that two in parallel should give
1A total charge current, but the 10 second lag will always be there.


Lee Hart wrote (on 4/23/06):

> Neon John wrote:
>  
>> I'm unhappy with the current practice and techniques of precharging
>> the controller caps.
>>    
>
> I'm using a 130v 75w light bulb as my precharge resistor. It precharges
> in a fraction of a second; far faster than the recommended 750 ohm
> resistor. Yet it still limits the current to a reasonable value.
>
> [snip]
> How about a really odd solution? Use a vacuum tube rectifier, like a
> 12X4. The isolated 12v filament is powered by your key switch. The
> cathode and anodes connect across your main contactor, to controller B+
> and pack+ respectively. To precharge, power the filament. A diode with
> some series resistance appears between anode and cathode, and the
> controller precharges.
>
>  

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Re: Precharge circuit preliminary test (was: Precharge alternatives)

TrotFox Greyfoot
Just a thought...

How are those tubes going to stand up against the vibrations in an EV?
 Have you thought about mounting them in such a way as to minimize bad
vibes?

Trot, the gray, fox...

On 8/14/07, Eric Poulsen <[hidden email]> wrote:

>
>
> [Cross-posted to evtech]
>
> I tried the vacuum tube method mentioned below last night.
>
> Charging a 6000uF cap bank from 0v to 30V with a 35V power supply took
> 18 seconds using both diodes in a 12x4 tube.  Ten seconds elapsed before
> there was any change in the capacitor voltage, probably because of the
> filament warm-up time.
>
> When I get a chance to bust out my super-dirty power supply (variac,
> rectifier, capacitor), I'll test it at 150VDC, and post the results.
>
> I bought two of the tubes, and I expect that two in parallel should give
> 1A total charge current, but the 10 second lag will always be there.


--
|  /\_/\       TrotFox         \ Always remember,
| ( o o ) AKA Landon Solomon \ "There is a
|  >\_/<       [hidden email]       \ third alternative."

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Re: Precharge circuit preliminary test (was: Precharge alternatives)

eric@zyxod.com
Having owned a car with a vacuum tube radio (that still worked 30 years
later), I don't think it's a problem.

Tube equipment is remarkably robust; most of the problems are with aging
components:

Bad paper or electrolytic capacitors
Dirty or corroded tube sockets
Bad selenium diodes

I have a 50-year-old LCR meter
(http://nuancesystems.net/equipment.shtml) that still has good tubes.

In any case, the effect that vibration usually has on tube amplifiers is
that the tube acts as a microphone, which isn't a concern in this
application.

TrotFox Greyfoot wrote:

> Just a thought...
>
> How are those tubes going to stand up against the vibrations in an EV?
>  Have you thought about mounting them in such a way as to minimize bad
> vibes?
>
> Trot, the gray, fox...
>
> On 8/14/07, Eric Poulsen <[hidden email]> wrote:
>  
>> [Cross-posted to evtech]
>>
>> I tried the vacuum tube method mentioned below last night.
>>
>> Charging a 6000uF cap bank from 0v to 30V with a 35V power supply took
>> 18 seconds using both diodes in a 12x4 tube.  Ten seconds elapsed before
>> there was any change in the capacitor voltage, probably because of the
>> filament warm-up time.
>>
>> When I get a chance to bust out my super-dirty power supply (variac,
>> rectifier, capacitor), I'll test it at 150VDC, and post the results.
>>
>> I bought two of the tubes, and I expect that two in parallel should give
>> 1A total charge current, but the 10 second lag will always be there.
>>    
>
>
>  
   

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Re: Precharge circuit preliminary test (was: Precharge alternatives)

David Wilker
In reply to this post by eric@zyxod.com
For those that don't know, it takes 5 time periods to charge or disharge a capacitor. You can determine the time period using the formula: Resistance times Capacitance equals time period (R X C = t) in seconds.

Showing off,
David C. Wilker Jr.
USAF (RET)

---- Eric Poulsen <[hidden email]> wrote:


[Cross-posted to evtech]

I tried the vacuum tube method mentioned below last night.

Charging a 6000uF cap bank from 0v to 30V with a 35V power supply took
18 seconds using both diodes in a 12x4 tube.  Ten seconds elapsed before
there was any change in the capacitor voltage, probably because of the
filament warm-up time.

When I get a chance to bust out my super-dirty power supply (variac,
rectifier, capacitor), I'll test it at 150VDC, and post the results.

I bought two of the tubes, and I expect that two in parallel should give
1A total charge current, but the 10 second lag will always be there.


Lee Hart wrote (on 4/23/06):

> Neon John wrote:
>  
>> I'm unhappy with the current practice and techniques of precharging
>> the controller caps.
>>    
>
> I'm using a 130v 75w light bulb as my precharge resistor. It precharges
> in a fraction of a second; far faster than the recommended 750 ohm
> resistor. Yet it still limits the current to a reasonable value.
>
> [snip]
> How about a really odd solution? Use a vacuum tube rectifier, like a
> 12X4. The isolated 12v filament is powered by your key switch. The
> cathode and anodes connect across your main contactor, to controller B+
> and pack+ respectively. To precharge, power the filament. A diode with
> some series resistance appears between anode and cathode, and the
> controller precharges.
>
>  

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Re: Precharge circuit preliminary test

Lee Hart
In reply to this post by TrotFox Greyfoot
TrotFox Greyfoot wrote:
> How are those tubes going to stand up against the vibrations in an EV?
> Have you thought about mounting them in such a way as to minimize bad
> vibes?

The 12X4 vacuum tube was specifically built for car radios in the
1950's. Vibration is not a problem. Cars nowdays are a lot smoother than
back then!

--
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

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