500A power source

[Winfield Hill]

In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.


--
Thanks,
- Win

 

[Winfield Hill]

John Larkin wrote...

MeanWell has a 5 volt 150 amp power supply for $180.
Parallel two of them.

The MeanWells can put out a bit more than rated
current for a while.

I'd need four of them to get to 8 to 10V. And I have
a pile of surplus half-rack 5V 200A supplies, could
wire up four of them. Also a few years back I made a
6V 400V rack-mount supply, that could probably do 500A
for a few seconds. Some parts I'd like to characterize
could get by with the lower D.U.T. voltage.


--
Thanks,
- Win

 

[Winfield Hill]

Winfield Hill wrote...

In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.

18650 Li-Ion cells, while they look impressive,
are actually really wimpy. 38120 LiFePO4 cells
look even more impressive, but still have rather
disappointingly-high internal resistance. Stack
four in series, esr is 4x higher yet, so you need
lots of parallel stacks. 66160 cells, of either
LiFePO4 or TLO chemistry have attractive low esr.
A two or three-volt drop at 500A isn't too bad.
Whoa, they're huge. I like TLO's safe operation.


--
Thanks,
- Win

 

[John Larkin]

On 1 Apr 2020 14:35:43 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.

MeanWell has a 5 volt 150 amp power supply for $180. Parallel two of
them.

The MeanWells can put out a bit more than rated current for a while.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Winfield Hill]

John Larkin wrote...

On 1 Apr 2020, Winfield Hill wrote:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.

Polyphase buck switcher?

Good idea, but it'd be a 5kW switcher, and
with enough bulk capacitance to last through
the 8ms troughs. Each of six phases running
at almost 100A. Sounds like more work than
putting together a battery.


--
Thanks,
- Win

 

[John Larkin]

On 1 Apr 2020 14:35:43 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.

Polyphase buck switcher?

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[legg]

On 1 Apr 2020 14:35:43 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.

The simpler the requirement, the simpler the
solution.

If all you needed was to duplicate the 8mS half-sine
forward surge current rating ( a non-repetitive
test ) for rectifiers, a pulse-forming circuit
could do it - but this is not really a linearly
controlled method, it's just a resonant hammer
that gets adjusted to suit pulse losses in the
DUT.

The period is set by the non-adjustible PFN.
The standard specifies a peak value of the half-sine.
At 1Hz, you might lose 40W in the circuit and DUT.

A PWM buck would reduce the current stress on the
source - so you'd not really be looking for a 500A
source, you'd be looking for something that can
supply the energy delivered to the DUT, and losses.

How this could be integrated into a linear test
circuit like the RS-796A, is a puzzler. Perhaps
PWMing the switch driver, outside of the linear
control loop, with a choke and rated freewheeling
diode might do it; but you'd have to sense the
current in the DUT, not the switch current. This
would defeats the RS-796A test modality, which
assumes Idut = Iswitch.

Sorry if slow on the draw here. Figured it was
a good time to catch up on paperwork, taxes etc.

RL

 

[Flyguy]

On Wednesday, April 1, 2020 at 2:35:51 PM UTC-7, Winfield Hill wrote:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.


--
Thanks,
- Win

Now you've changed it to 8 to 10V, before it was just 10V. LFP cell voltage is 3.2V, so you only need 3, given cells with low enough internal resistance to keep the voltage from dropping below 8V. What you won't get is an integrated BMS, so you will have to take appropriate precautions. I suggested an external resistor to take part of the load off of the MOSFET.

 

[Winfield Hill]

Lasse Langwadt Christensen wrote...

skrev Winfield Hill:
In my search for a 8 to 10V, 500A source,
needed for 2 seconds ...

something like this?
https://hobbyking.com/en_us/turnigy-graphene-6000mah-3s-75c-lipo-pack-w-xt90.html

Whoa, cotta check that out.


--
Thanks,
- Win

 

[Winfield Hill]

Flyguy wrote...

I suggested an external resistor to take part of
the load off of the MOSFET.

But which of the five or six battery-configuration
choices do you recommend?


--
Thanks,
- Win

 

[Lasse Langwadt Christense]

onsdag den 1. april 2020 kl. 23.35.51 UTC+2 skrev Winfield Hill:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.

something like this? https://hobbyking.com/en_us/turnigy-graphene-6000mah-3s-75c-lipo-pack-w-xt90.html

 

[Clive Arthur]

On 01/04/2020 22:35, Winfield Hill wrote:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.


Supercaps?

--
Cheers
Clive

 

On 1 Apr 2020 14:35:43 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds,

Since you need 2 seconds and you have three phase available on site,
why not use a three phase transformer and a six pulse rectifier ?

If you can't find a three phase transformer (or three single phase
transformers) with exact voltage, get a transformer with slightly
higher secondary voltage than needed and replace three or all six
rectifiers with SCRs and adjust the firing angles for voltage fine
adjustment.

A 5 to 6 Vrms phase to neutral secondary voltage should be quite
suitable. About 200 A/phase secondary current would be required, With
a 120 V / 6 V turns ratio that makes 10 A/phase on primary side.

Using wye/delta configurations on primary and/or secondary side might
increase the number of suitable ready made transformers available.

 

[Uwe Bonnes]

Clive Arthur <cliveta@nowaytoday.co.uk> wrote:

On 01/04/2020 22:35, Winfield Hill wrote:
In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.

Something like 10 kF will be needed for 500 A, 2 sec and 0.1 Volt drop
--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 1623569 ------- Fax. 06151 1623305 ---------

 

[Chris Jones]

On 02/04/2020 20:28, Uwe Bonnes wrote:

Clive Arthur <cliveta@nowaytoday.co.uk> wrote:
On 01/04/2020 22:35, Winfield Hill wrote:
In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells,
in 38120 and 66160 sizes. All types of
suppliers, plus completed battery systems,
with charge balancing electronics. Sheesh,
it's enough to make one's head spin. BTW,
a simple "12V" battery has a bit too much
voltage, an extra burden on power MOSFET(s),
so cell-by-cell connectivity would be nice.
Probably gonna be at least $500, no matter.
Gotta ask Rob Legg what he thinks.

Something like 10 kF will be needed for 500 A, 2 sec and 0.1 Volt drop

Why would you want or need only 0.1V drop? 1V or even 2V drop would
surely do. 3kF capacitors are fairly inexpensive from digi-key. The ones
I have are rated for about 1.9kA and if I recall correctly about 0.3
milliohms series resistance. You'd need at least 3 in series, meaning at
most 1kF total capacitance from a single string but that should be fine.

 

[Winfield Hill]

upsidedown@downunder.com wrote...

On 1 Apr 2020 14:35:43 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds,

Since you need 2 seconds and you have three phase
available on site, why not use a three phase
transformer and a six pulse rectifier ?

Yes, we already agreed that's a viable solution.
But looking around for suitable transformer(s),
I wasn't able to find much. Yes, looking in
the wrong place, no doubt.


--
Thanks,
- Win

 

[Winfield Hill]

Chris Jones wrote...

On 02/04/2020 20:28, Uwe Bonnes wrote:
Clive Arthur <cliveta@nowaytoday.co.uk> wrote:
On 01/04/2020 22:35, Winfield Hill wrote:
In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells

Something like 10 kF will be needed for 500 A,
2 sec and 0.1 Volt drop

Why would you want or need only 0.1V drop?
1V or even 2V drop would surely do.

I can handle 2V drop, and while the peak current
will be 500A, the RMS current will only be 177A.
About $112 worth of capacitors would do for a
33ms 2-cycle budget - simple and very useful.
But a full 100-cycle capability looks like it
would be much more expensive than batteries.


--
Thanks,
- Win

 

[Michael Terrell]

On Thursday, April 2, 2020 at 8:35:47 AM UTC-4, Winfield Hill wrote:

upsidedown wrote...

On 1 Apr 2020 14:35:43 -0700, Winfield Hill wrote:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds,

Since you need 2 seconds and you have three phase
available on site, why not use a three phase
transformer and a six pulse rectifier ?

Yes, we already agreed that's a viable solution.
But looking around for suitable transformer(s),
I wasn't able to find much. Yes, looking in
the wrong place, no doubt.

The main power transformer from one piece of broadcast NTSC video equipment I maintained in the late '80s had a 1000A, regulated 5VDC power supply that was over a half ton. It ran on 208, three phase. It was in a Vital Industries 'SqueezeZoom. It was the first electronic special effects system of its kind, and it sold for US $250,000. One was used at the studio that produced the Sonny and Cher show, where they came back on stage in all the costumes they wore throughout the show, with no loss of video quality. Sadly most or all were scraped when TV went digital. Some industrial surplus stores might turn up similar transformers. Mendelson's, in Dayton Ohio used to have tons of large, low voltage transformers from early mainframes.

 

[Winfield Hill]

Michael Terrell wrote...

On Thursday, April 2, 2020, Winfield Hill wrote:
upsidedown wrote...
Winfield Hill wrote:

In my search for a 8 to 10V, 500A source,
needed for 2 seconds ...

Since you need 2 seconds and you have three phase
available on site, why not use a three phase
transformer and a six pulse rectifier ?

Yes, we already agreed that's a viable solution.
But looking around for suitable transformer(s),
I wasn't able to find much. Yes, looking in
the wrong place, no doubt.

The main power transformer from one piece of broadcast
NTSC video equipment I maintained in the late '80s had a
1000A, regulated 5VDC power supply that was over a half ton.
It ran on 208, three phase. It was in a Vital Industries
'SqueezeZoom. It was the first electronic special effects
system of its kind, and it sold for US $250,000. One was
used at the studio that produced the Sonny and Cher show,
where they came back on stage in all the costumes they wore
throughout the show, with no loss of video quality. Sadly
most or all were scraped when TV went digital. Some
industrial surplus stores might turn up similar transformers.
Mendelson's, in Dayton Ohio used to have tons of large, low
voltage transformers from early mainframes.

Wow, impressive. But I actually may not need a
high VA rating, because I'm only drawing current
for 2 seconds. I do need low winding resistance.
350A for 8ms, 177A for 33ms, down to 20A for 2 sec.
Hopefully no more than 3V drop at 350A = 8mR max.
Probably not a low number compared to your story.


--
Thanks,
- Win

 

[Chris Jones]

On 02/04/2020 23:46, Winfield Hill wrote:

Chris Jones wrote...

On 02/04/2020 20:28, Uwe Bonnes wrote:
Clive Arthur <cliveta@nowaytoday.co.uk> wrote:
On 01/04/2020 22:35, Winfield Hill wrote:
In my search for a 8 to 10V, 500A source,
needed for 2 seconds, I've been looking at
LiFePO4, and LTO (Lithium Titanate) cells

Something like 10 kF will be needed for 500 A,
2 sec and 0.1 Volt drop

Why would you want or need only 0.1V drop?
1V or even 2V drop would surely do.

I can handle 2V drop, and while the peak current
will be 500A, the RMS current will only be 177A.
About $112 worth of capacitors would do for a
33ms 2-cycle budget - simple and very useful.
But a full 100-cycle capability looks like it
would be much more expensive than batteries.

So if you had 4x Maxwell BCAP3000P270, total price $256, that would give
you 750F at 10.8V initial voltage. After 2 seconds of 500A DC, it would
discharge by 1.33V to about 9.46V. The internal resistance would drop
another 580mV, so it would be down to 8.88V at the capacitor terminals
whilst the current is still on. You would not be running 500A DC for the
whole 2 seconds if you are doing half-sine waveforms, so it would not be
as bad as that. Also if you got keen, you could upgrade it to do 1.9kA
for shorter periods with the same capacitors.

Those capacitors are very light too. I was thinking of making a cordless
spotwelder with a series parallel array of those capacitors, but for say
10kA welding current, the MOSFETs to regulate the current (or even just
turn it off at the end of a weld) look like they will be expensive or
big, and I haven't had time to work on it.