500A power source

 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

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

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

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

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

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

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.

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 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

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