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Discussion Starter #1
Hi Folks,

I've been having a difficult time finding a DC-DC converter that can
handle 370v DC (max 400v). The only ones I've found tend to be VERY
pricey and don't have that much power.

A coworker of mine suggested that I could use an AC-DC converter as a
DC-DC converter, as long as the rated (voltage * 1.4) was high enough.
Meaning, I'd need an AC-DC converter that could handle 285v AC and
produced 13.8v DC.

Does this make sense to you? If so, could someone point me to some
readily available examples?

Thanks in advance,
Peter
http://www.evalbum.com/2784



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Discussion Starter #2
Peter C. Thompson wrote:
> I've been having a difficult time finding a DC-DC converter that can
> handle 370v DC (max 400v). The only ones I've found tend to be VERY
> pricey and don't have that much power.
>
> A coworker of mine suggested that I could use an AC-DC converter as a
> DC-DC converter, as long as the rated (voltage * 1.4) was high enough.
> Meaning, I'd need an AC-DC converter that could handle 285v AC and
> produced 13.8v DC.

Look for a "power factor corrected" power supply with the desired output
voltage and current. This type of supply has a) a rectifier that
converts the incoming 50/60 Hz AC into DC, b) a boost converter that
increases this DC voltage to about 400vdc, and c) a 400vdc-to-whatever
output voltage DC/DC converter.

In your case, the only stage you need is the final one, since you
already have a 400vdc power source. You can take the supply apart and
tap into it at the desired point (easy to find; it goes to the big
450vdc rated electrolytic capacitors). Or better yet, find a power
factor corrected supply that lists *both* AC and DC input specs, and
simply use it as-is.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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Discussion Starter #3
Another option is to run 2 lower power DC-DCs, each on it's own half
of your pack. This way you won't unbalance the pack and you can
parallel the outputs.

I'm running a Vicor power supply. It's a PFC supply rated for 120 -
230 VAC or 300 VDC. That means it will be happy anywhere from 168 to a
little over 300 VDC. It's NOT one of the ones that's labeled
100-120/200-240. My pack is 219 nominal, rests briefly at 250 after a
charge, and sags as low as 150 when I'm having fun. The Vicor seems
pretty content, but I do have a 12v house battery also.

My Vicor has been happy so far this year, we'll see if it keeps taking
the abuse.

Dave Cover

Lee Hart <[email protected]> wrote:
> Peter C. Thompson wrote:
>> I've been having a difficult time finding a DC-DC converter that can
>> handle 370v DC (max 400v). The only ones I've found tend to be VERY
>> pricey and don't have that much power.
>>
>> A coworker of mine suggested that I could use an AC-DC converter as a
>> DC-DC converter, as long as the rated (voltage * 1.4) was high enough.
>> Meaning, I'd need an AC-DC converter that could handle 285v AC and
>> produced 13.8v DC.
>
> Look for a "power factor corrected" power supply with the desired output
> voltage and current. This type of supply has a) a rectifier that
> converts the incoming 50/60 Hz AC into DC, b) a boost converter that
> increases this DC voltage to about 400vdc, and c) a 400vdc-to-whatever
> output voltage DC/DC converter.
>
> In your case, the only stage you need is the final one, since you
> already have a 400vdc power source. You can take the supply apart and
> tap into it at the desired point (easy to find; it goes to the big
> 450vdc rated electrolytic capacitors). Or better yet, find a power
> factor corrected supply that lists *both* AC and DC input specs, and
> simply use it as-is.
> --
> Lee A. Hart | Ring the bells that still can ring
> 814 8th Ave N | Forget the perfect offering
> Sartell MN 56377 | There is a crack in everything
> leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
>
> _______________________________________________
> | REPLYING: address your message to [email protected] only.
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>



-- =

http://www.evalbum.com/2149

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Discussion Starter #4
Many EV'ers use Iota AC-DC converters running from their pack.
While it is not the highest quality equipment available,
I expect that a 230V AC model will do exactly what you want.
Every 230V AC equipment that I have seen uses a rectifier
and capacitor that is rated for at least 400V DC.

Success,

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Peter C. Thompson
Sent: Thursday, September 16, 2010 4:33 AM
To: Electric Vehicle Discussion List
Subject: [EVDL] Repurposing an AD-DC convert to a DC-DC converter

Hi Folks,

I've been having a difficult time finding a DC-DC converter that can
handle 370v DC (max 400v). The only ones I've found tend to be VERY
pricey and don't have that much power.

A coworker of mine suggested that I could use an AC-DC converter as a
DC-DC converter, as long as the rated (voltage * 1.4) was high enough.
Meaning, I'd need an AC-DC converter that could handle 285v AC and
produced 13.8v DC.

Does this make sense to you? If so, could someone point me to some
readily available examples?

Thanks in advance,
Peter
http://www.evalbum.com/2784



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Discussion Starter #5
Hello Peter,

I have been using a 110-240VAC to 48VDC PSU (I think is was designed
for a printer) to supply 48V to part of my EV system that normally
uses a tap off the traction pack - it supplies power for the
controller cooling fan and the main contactor. It has worked well for
several thousand miles and the main reason I used it was to eliminate
the imbalance it creates on the traction pack which would only have to
be corrected using the charger in 'balancing' or 'equalizing' mode -
rather a waste of power... and just rather annoying and inelegant, if
you will. For simple, non-silicon based loads and circuits this is
fine. Curiously, the PSU appeared to be polarity sensitive on the
input side but worked down to around 100VDC input.

However, when I tried doing the same for the 24V supply the system
needs, using a mains to 24V PSU designed I believe for a macBook, I
ran into an issue which it seems was caused by the PSU allowing a
momantary spike of high DC volts through to the controller at start
up. This fried a few silicon based components in the controller that
were obviously not rated for the 120VDC that my traction pack is.

If you only have lights etc to worry about then you'll probably be
OK. But for any modern vehicle systems with PCB's for this and that
you will have to be very careful. I don't know if you have the
equipment to test for such a possibility.... perhaps a transient
suppressor (such as a varistor) might eliminate the risk?

Regards, Martin Winlow
Herts, UK
http://www.evalbum.com/2092
www.winlow.co.uk


Peter C. Thompson wrote:

> Hi Folks,
>
> I've been having a difficult time finding a DC-DC converter that can
> handle 370v DC (max 400v). The only ones I've found tend to be VERY
> pricey and don't have that much power.
>
> A coworker of mine suggested that I could use an AC-DC converter as a
> DC-DC converter, as long as the rated (voltage * 1.4) was high enough.
> Meaning, I'd need an AC-DC converter that could handle 285v AC and
> produced 13.8v DC.
>
> Does this make sense to you? If so, could someone point me to some
> readily available examples?
>
> Thanks in advance,
> Peter
> http://www.evalbum.com/2784
>




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