Author Topic: Cheezeball DC Load: DL24P: Pump, or Dump ???  (Read 77801 times)

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Offline frogblenderTopic starter

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Cheezeball DC Load: DL24P: Pump, or Dump ???
« on: September 20, 2020, 01:59:08 pm »
Anyone have the DC Load shown in the pic?  If so, please post your thoughts.

$42USD delivered, 180W, 200V, 20A, full-disco LCD display, low-voltage cutoff,  bluetooth connection to bug-ridden app.  What else could one want?  Seems great to me.

https://bit.ly/2ZVbN8x

 
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Offline No.15

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #1 on: September 20, 2020, 02:02:25 pm »
I had a similar one and it let the magic smoke out on the third use
 

Offline Grandchuck

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #2 on: September 21, 2020, 09:20:41 pm »
I have one and can report mixed feelings about it.  The software is useless.  The current is noticeably jittery at low values in CC mode.  However, it is sometimes handy to have around.  The photo shows the external temperature sensor being used to monitor the heatsink of the switching FET of the power supply.
 
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Offline interflexo

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #3 on: September 27, 2020, 06:12:02 pm »
I had plans to use it (proof of concept only) at half the max power in a computer USB controlled project.

The USB/Bluetooth reported voltage, capacity and temperatures lack the screen resolution.

The remote setup is achieved by emulating the user interface button clicks. You can't use the buttons long press modes to access or change some parameters. You can't inquire any of the programmed settings or where is the cursor blinking. It's like trying to configure the unit by hand but using a blindfold. Who in his right mind would release a product like this?

The unit has an internal and an external NTC.

There is a new unit available with added remote voltage sense.
https://de.aliexpress.com/item/1005001458325206.html?spm=a2g0o.productlist.0.0.3822ccf1zniWmj&algo_pvid=219f12ff-32b4-4855-bf41-41d5690f1ee2&algo_expid=219f12ff-32b4-4855-bf41-41d5690f1ee2-7&btsid=0bb0623116012052587916854ed059&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
« Last Edit: September 27, 2020, 06:18:21 pm by interflexo »
 
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Offline frogblenderTopic starter

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #4 on: October 08, 2020, 08:03:49 pm »

There is a new unit available with added remote voltage sense.
https://de.aliexpress.com/item/1005001458325206.html?spm=a2g0o.productlist.0.0.3822ccf1zniWmj&algo_pvid=219f12ff-32b4-4855-bf41-41d5690f1ee2&algo_expid=219f12ff-32b4-4855-bf41-41d5690f1ee2-7&btsid=0bb0623116012052587916854ed059&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

Do you have any experience with this newer revision?   The fact that these guys are coming out with newer revisions is a good sign.  Any idea about reflashing latest firmware?
 

Offline frogblenderTopic starter

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #5 on: October 08, 2020, 08:11:20 pm »
I had a similar one and it let the magic smoke out on the third use
Apparently there's a design flaw where voltage spikes above 20v get onto the fet's gate, blowing it up.   You can probably fix permanently with a new fet and a 15v zener.  https://syonyk.blogspot.com/2018/06/the-atorch-purple-fan-mosfet-destroyer.html
 
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Offline frogblenderTopic starter

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #6 on: October 08, 2020, 08:21:06 pm »
I have one and can report mixed feelings about it.  The software is useless.  The current is noticeably jittery at low values in CC mode.  However, it is sometimes handy to have around.  The photo shows the external temperature sensor being used to monitor the heatsink of the switching FET of the power supply.

Couple of quick questions, if you could:
1) Once it hits the low-voltage-cutoff and turns off.... does it stay off (at least until user intervention)?   Earlier versions apparently hit the cutoff, turn off, but then turn back on as soon as the voltage drifts back up above the cutoff (which every battery known to mankind will do)

2)  Is there any output on this thing that can be used to switch a relay ?   I want a battery tester that'll discharge a battery down to my specified cutoff, then switch in a charger or my choosing.  I know this is alot to ask....


 

Offline frogblenderTopic starter

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #7 on: October 08, 2020, 08:23:24 pm »
I have one and can report mixed feelings about it.  The software is useless.  The current is noticeably jittery at low values in CC mode.  However, it is sometimes handy to have around.  The photo shows the external temperature sensor being used to monitor the heatsink of the switching FET of the power supply.
Hey, wait... were you making a wisecrack here?  "It is useless, unless you only need a cheap thermometer, in which case it's handy to have around!"
 

Offline Grandchuck

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #8 on: October 09, 2020, 12:40:17 pm »
I have one and can report mixed feelings about it.  The software is useless.  The current is noticeably jittery at low values in CC mode.  However, it is sometimes handy to have around.  The photo shows the external temperature sensor being used to monitor the heatsink of the switching FET of the power supply.

Couple of quick questions, if you could:
1) Once it hits the low-voltage-cutoff and turns off.... does it stay off (at least until user intervention)?   Earlier versions apparently hit the cutoff, turn off, but then turn back on as soon as the voltage drifts back up above the cutoff (which every battery known to mankind will do)

2)  Is there any output on this thing that can be used to switch a relay ?   I want a battery tester that'll discharge a battery down to my specified cutoff, then switch in a charger or my choosing.  I know this is alot to ask....

1)  It stays off.
2)  No output for that.
 
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Offline duckduck

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #9 on: October 09, 2020, 06:30:17 pm »
Anyone have the DC Load shown in the pic?

I had the 150W version (ATORCH DL24). I did not test its accuracy, but it seemed to function OK. Build quality seemed decent enough. I didn't ever use the PC software or Bluetooth. It was very handy for seeing which USB chargers are decent and which are crap. I did some unnecessary surgery and destroyed it. You might consider making a case for it. It's pretty easy to damage the bare PCB if you are not careful. I paid US$26 plus a couple of bucks for shipping. I don't know that I'd pay US$42, but then I just bought it to play with.
 
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Offline frogblenderTopic starter

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #10 on: October 29, 2020, 08:11:32 pm »
SO I bought the version that doesn't come with a heatsink - you must add your own.   1000W, don't ya know.   https://www.aliexpress.com/item/1005001345772275.html

1)  The included 12v PSU is garbage.   It cuts out intermittently, and you will waste an hour or 4.  Roundbin it immediately.

2)  The FET will promptly explode.  The problem outlined by Syonyk (https://syonyk.blogspot.com/2018/06/the-atorch-purple-fan-mosfet-destroyer.html) still exists.  I think the problem is an opamp stage driving the fet:  it is bode unstable, and the oscillations exceed the ±20v Vgs spec.     My fet failed short circuit - which will cause big problems if connected straight to a Lipo battery (it's funny that the brand name is "ATORCH" - this should be taken literally).

Replaced FET with FDH44N50.   The specs to look for in this application:  1) lowest possible °C/Watt on Junction-to-case,  and, 2)  175°C max junction temp (most big fets are 150). 

I put a 16v Zener from gate to source to clamp the oscillations.  There's probably an easier/better fix by changing something in the opamps' (there are multiple) feedback loop to improve stability, but I was too lazy.

3)  Heatsink:  my heatsink box yielded a nice copper sink with blower (not fan), 12v @ .8A, harvested from some old compaq P4.   I drilled/tapped a 6-32 thread in the copper, and a screw holds it nice and hard against the fet.

4) Do not use the included white plastic standoffs - they interfere with your heatsink.  Use rubber feet.

5) One other problem:  there is a TO252 diode on the PCB, with a .7v forward drop.  At the ATORCH's rated 20A... that's 14watts into the PCB, which may already be stinking hot from the fet.  If you run high power at high amperage... I can foresee melted solder on the TO252.


Anyway, it works pretty good now.  Reasonable accuracy (at higher voltages/currents at least;  I didn't test a low current.   You might have problems if you want to characterize an LR44 or somesuch). 

I put 250W through it for a couple of hours, draining a 48V ebike battery, with no issues.

I put 500W through it for maybe 10 seconds, before dialing it back cuz I'm chicken.   I wouldn't trust it more than maybe 300W.

Overall, not bad.  For the money, it is alot of watts.

 
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Offline ptluis

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #11 on: November 18, 2020, 01:59:10 pm »
SO I bought the version that doesn't come with a heatsink - you must add your own.   1000W, don't ya know.   https://www.aliexpress.com/item/1005001345772275.html

1)  The included 12v PSU is garbage.   It cuts out intermittently, and you will waste an hour or 4.  Roundbin it immediately.

2)  The FET will promptly explode.  The problem outlined by Syonyk (https://syonyk.blogspot.com/2018/06/the-atorch-purple-fan-mosfet-destroyer.html) still exists.  I think the problem is an opamp stage driving the fet:  it is bode unstable, and the oscillations exceed the ±20v Vgs spec.     My fet failed short circuit - which will cause big problems if connected straight to a Lipo battery (it's funny that the brand name is "ATORCH" - this should be taken literally).

Replaced FET with FDH44N50.   The specs to look for in this application:  1) lowest possible °C/Watt on Junction-to-case,  and, 2)  175°C max junction temp (most big fets are 150). 

I put a 16v Zener from gate to source to clamp the oscillations.  There's probably an easier/better fix by changing something in the opamps' (there are multiple) feedback loop to improve stability, but I was too lazy.

3)  Heatsink:  my heatsink box yielded a nice copper sink with blower (not fan), 12v @ .8A, harvested from some old compaq P4.   I drilled/tapped a 6-32 thread in the copper, and a screw holds it nice and hard against the fet.

4) Do not use the included white plastic standoffs - they interfere with your heatsink.  Use rubber feet.

5) One other problem:  there is a TO252 diode on the PCB, with a .7v forward drop.  At the ATORCH's rated 20A... that's 14watts into the PCB, which may already be stinking hot from the fet.  If you run high power at high amperage... I can foresee melted solder on the TO252.


Anyway, it works pretty good now.  Reasonable accuracy (at higher voltages/currents at least;  I didn't test a low current.   You might have problems if you want to characterize an LR44 or somesuch). 

I put 250W through it for a couple of hours, draining a 48V ebike battery, with no issues.

I put 500W through it for maybe 10 seconds, before dialing it back cuz I'm chicken.   I wouldn't trust it more than maybe 300W.

Overall, not bad.  For the money, it is alot of watts.


I like it, it's cheap, works fair enough but definitely the diode mod is necessary.
I don't like the way they erase the main chips reference, but anyway I've found out what the microprocessor is, second chip from the left, it's an HC32F030E8PA  ARM Cortex-M0+, 48 MHz
 https://www.keil.com/dd2/hdsc/hc32f030e8pa/
The other chip on it's left I couldn't find out. if anybody knows tell us.

I bought the dl24p and the new version dl24p 4 wire. This 4 wire version doesn't have the dc-dc chip MC34063A.
Regarding the dl24p 2 wire version, this one (4 wire) starts faster, but both have the same firmware 5.1.
I only tested those units at low current máx 2 Amps or 30w max, because I didn't have proper heatsink available at the moment and my available time for electronics is short at the moment.


 

Offline radud5

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #12 on: January 16, 2021, 09:42:17 am »
How to upgrade DL24 to 4wire in Russian (blue line is interrupted and red line is short) https://youtu.be/ITKDrbPwFx8 . The text can be translated with google android  translate from photo/camera.
« Last Edit: January 16, 2021, 10:07:03 am by radud5 »
 
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Offline ptluis

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #13 on: January 25, 2021, 06:50:38 pm »
It worked for me.

Following two images with simple instructions from video

Step 1
* Step1.jpg (101.64 kB. 1343x470 - viewed 1565 times.)

Step 2
* Step2.jpg (136.94 kB. 1312x853 - viewed 1577 times.)
 

Offline Elasia

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #14 on: January 25, 2021, 06:58:59 pm »
Looks like house fire
 
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Offline ptluis

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #15 on: January 25, 2021, 07:08:24 pm »
mine still alive  :) do it at your own risk. Worked for me, but needed a microscope to cut things  ;D

BTW my DL24 is modded. I add a 15v zener diode between mosfet gate and source to reduce 20v+ spikes existing on gate. I also add a 47 ohm in series between gate driver and mosfet gate to reduce the rigging i'm having on this mosfet. Now working ok. no problems at the moment.
« Last Edit: January 25, 2021, 07:15:31 pm by ptluis »
 

Offline fubgumfaw

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #16 on: February 22, 2021, 11:12:44 pm »
I just got a DL24P. I've had it just days now. I'm seeing some weirdness...
1. At 48v or higher it will work at 180 watts. I haven't tried something between 12v and 48v yet to see what that actual cut-off is.
2. I tried a bunch of 21700 cells in parallel so I could run it at 4.1v. MAX I could get out of it was 6.8 amps or almost 28 watts...disappointing!
3. I tried it on a 12v SLA battery and that too would not get to 180 watts. I see around 120 watts max.
4. Has anyone found firmware for these things? I'm wondering if maybe I have old firmware and that is causing the current limiting at lower voltages.
5. I wondered if that diode would get hot and it sure does! It needs a heat sink ASAP! I think I'll pull off the factory one and add a larger one. Any suggestions on a solid copper one that will fit and get to the diode too?
6. I have not seen 20 amps max ever. 4.1v should have gotten me that!
7. I'll have to sort through my zeners. I'm sure I have a 15v zener...
8. I saw one poster who blew their Chinese mosfet. Since the mosfet is doing all the work, I was thinking about the Rds. I found lower Rds mosfets than the factory one. This would drop the heat on the mosfet considerably. The thing I wondered about is how will the mosfet Rds effect the current sensing? I suspect that the 2 shunts on the board are how that is measured, but thought I'd check before I swapped out the Chinese mosfet for a much better one.
9. Just to be sure here, I was going to go for the lowest Rds and the highest wattage I could find. Anything else matter for this application?
11. People that are running at over 180 watts, are you just changing the wattage setting or is there something else too?
12. Anyone tried for 1000 watts like the aliexpress ad reports? NO way that's possible without heat sinking the diode!


Edit: Looking at mosfets...
The IXTX110N20L2  has the lowest Rds and the highest wattage I could find in a 200v mosfet. Rds is 24mOhms and 960 watts. Vgs is 20v continuous so with that 15v zener that should be OK. That's awfully close to that magical 1000 watts. All of this is better than the factory mosfet by a lot! Not particularly cheap at $25 on Mouser! Still...180 watts was not enough IMHO. I knew buying it that I was going to want more than the fiddly 180 watts.

The factory 12v PSU is pretty noisy. It does work, but better filtering would help it a lot. I'm going to crack mine open and add a bigger cap on the 12v line. Inside that tiny box...I bet it's like 220uF! Worst case I have several small 12v PSU's that can work here.

I have an old square CPU heat sink. I think it might work in place of the factory one and reach over to the diode too.
« Last Edit: February 23, 2021, 12:10:33 am by fubgumfaw »
 

Offline frogblenderTopic starter

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #17 on: February 23, 2021, 02:29:50 am »
I found lower Rds mosfets than the factory one. This would drop the heat on the mosfet considerably
I have an old square CPU heat sink. I think it might work in place of the factory one and reach over to the diode too.

rdsOn doesn't matter at all in this application - the fet is operating in its linear region (ie. the fet is never fully "on", as in rds"on").

The fet specs you want are:   
- lowest possible junction-to-case °C/W
- 175°C operating temperature (most big mosfets are 150°C)
- highest power handling
- VGS of  20v  or more (cuz of the dumb ringing on the gate driver amp, that blows up the fet.  That's what the zener is for.  A better fix would be to figure out how to stabilize the opamp that drives the gate).

The best I could find is FDH44N50

The diode and your fet are likely two different heights, making both sharing the same heatsink problematic. 

I think the diode is there strictly for reverse polarity protection.  The problem is it is not schottky, so it will smolder at least 0.7W per amp you shove through it.  But schottky's generally have poorer reverse-voltage standoff. 

 

Offline fubgumfaw

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #18 on: February 23, 2021, 05:59:38 am »
I found lower Rds mosfets than the factory one. This would drop the heat on the mosfet considerably
I have an old square CPU heat sink. I think it might work in place of the factory one and reach over to the diode too.

rdsOn doesn't matter at all in this application - the fet is operating in its linear region (ie. the fet is never fully "on", as in rds"on").

The fet specs you want are:   
- lowest possible junction-to-case °C/W
- 175°C operating temperature (most big mosfets are 150°C)
- highest power handling
- VGS of  20v  or more (cuz of the dumb ringing on the gate driver amp, that blows up the fet.  That's what the zener is for.  A better fix would be to figure out how to stabilize the opamp that drives the gate).

The best I could find is FDH44N50

The diode and your fet are likely two different heights, making both sharing the same heatsink problematic. 

I think the diode is there strictly for reverse polarity protection.  The problem is it is not schottky, so it will smolder at least 0.7W per amp you shove through it.  But schottky's generally have poorer reverse-voltage standoff.

Of course...the Rds doesn't matter if the mosfet is not fully turned on. I was not expecting it being in it's linear zone. I was assuming the mosfet was getting a PWM signal.

IXTH130N20T is probably a better option: (not the IXTX110N20L2 which is 150C)
200v, 175C, 130 amps, 830w, 30v Vgs
I'll never use this thing at over about 130v. I will never care about 200 or more.

The FDH44N50:
500v, 175C, 44 amps, 750w, 30v Vgs

The 2 things I see in favor of the IXTH130N20T are the package watts (830w vs 750w) and the amperage (130a vs 40a).
Did I miss anything?

I think you are right about the diode. There is no backwards current flow in a mosfet junction. The back diode is the only "reverse" current path . Back diodes are never going to hold up well to a dead short situation so I bet that "protection' diode is there to protect from the back diode being a current path. I think I'll replace it with something a bit larger In a TO-247 package. This will also make for a level surface for the heat sink across both components. I have a lot of them...probably have a 50a diode or better.

I bought a couple of solid copper CPU heat sinks to use. Each one is slightly smaller than the total area I need to fit over the diode and mosfet. I'll trim off a section of one and then solder that to the other one. There is no way it will get hot enough to melt the solder!
« Last Edit: February 23, 2021, 06:03:09 am by fubgumfaw »
 

Offline frogblenderTopic starter

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #19 on: February 23, 2021, 06:44:58 am »
The 2 things I see in favor of the IXTH130N20T are the package watts (830w vs 750w) and the amperage (130a vs 40a).
Did I miss anything?

You should add thermal resistance to your list as well - the IXTH130N20T is a bit better.
40a is more than the diode will handle, unless you have good heatsinking on it, and/or swap in a schottky, and/or jumper it.

830w vs 750w - I doubt you can get this without chilled water cooling or LN2 or something.  IIR the chinglish manual that came with mine (hey, at least it had a manual) spoke of paralleling fets.  I'm not sure if this would work (hinges on whether the temperature coefficient is positive or negative, and I can't remember what fets are *EDIT: fets have positive tempco:  resistance increases with temperature, so paralleling identical partnumbers should be ok), and there is the mechanical hassle of a bunch of thick wires and fets and big heatsinks all hanging loose.

Anyhoo... my record is 300W sustained.  Let us know what you achieve.

 

Offline capt bullshot

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #20 on: February 23, 2021, 06:57:30 am »

The 2 things I see in favor of the IXTH130N20T are the package watts (830w vs 750w) and the amperage (130a vs 40a).
Did I miss anything?


The IXTH130N20T datasheet doesn't show the SOA plot, while the FDH44N50 does, including DC. It's the first thing to look at if you want to use a MOSFET in its linear operating region.
Safety devices hinder evolution
 
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Offline mnementh

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #21 on: February 23, 2021, 06:29:39 pm »
I have a couple of the bare-board version coming. Is the original FET a IRFP260N of dubious origin, either reclaimed or counterfeit, as some of the review comments suggest?

Also, as I can't see them from the pics... what are the shunt resistors on this board? Will I need to plan on rebuilding the stack to be able to pull 20A through them without fireworks?

mnem
*taking a punt*
« Last Edit: February 23, 2021, 06:38:19 pm by mnementh »
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Offline fubgumfaw

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #22 on: February 23, 2021, 08:16:42 pm »
The 2 things I see in favor of the IXTH130N20T are the package watts (830w vs 750w) and the amperage (130a vs 40a).
Did I miss anything?

You should add thermal resistance to your list as well - the IXTH130N20T is a bit better.
40a is more than the diode will handle, unless you have good heatsinking on it, and/or swap in a schottky, and/or jumper it.

830w vs 750w - I doubt you can get this without chilled water cooling or LN2 or something.  IIR the chinglish manual that came with mine (hey, at least it had a manual) spoke of paralleling fets.  I'm not sure if this would work (hinges on whether the temperature coefficient is positive or negative, and I can't remember what fets are *EDIT: fets have positive tempco:  resistance increases with temperature, so paralleling identical partnumbers should be ok), and there is the mechanical hassle of a bunch of thick wires and fets and big heatsinks all hanging loose.

Anyhoo... my record is 300W sustained.  Let us know what you achieve.

I'm going to replace the diode with a bigger one. I have lots of half wave bridges in TO-247. Many are 40-60 amps. I don't need a fast diode for DC. I'll parallel the 2 diodes inside. Between the amperage increase and the TO-247 package, I can put the same heat sink over the mosfet and the diode bridge. That ought to get the amperage through the diode bumped up significantly and still have the protection in place. I doubt I'll ever make the mistake of reverse connecting anything, but still...good to have it in there.

I'm not sure how hot the mosfet will get. I figure more package wattage is better than less. I am shooting for that 1000 watt mark from the load tester. I bought some solid copper heat sinks to use in place of the aluminum one. I bought 4 of these. I'm not sure how many will fit on end across the width of the board. I'll screw/solder them to a copper plate which will be the heat spreader for the mosfet and diode. Between the copper and the significant additional surface area, I bet I have no issues with heat in the diode or mosfet. Probably beef up some traces too if it's needed.
https://www.ebay.com/itm/408296-001-HP-CPU-Processor-HeatSink-ProLiant-DL145-G2-389010-002/372618563641?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Paralleling the mosfets...I did think about doing that too. To that end, I'll buy several of the same mosfet. At $6 each...this is cheap and easy to do.

All of this will make the load tester bigger and top heavy, but it will get mounted to a piece of 6061 anyway and then the bottom of the board will also conduct heat to the aluminum. IF all of this isn't enough, what will be?
 

Offline fubgumfaw

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #23 on: February 23, 2021, 08:28:32 pm »
I have a couple of the bare-board version coming. Is the original FET a IRFP260N of dubious origin, either reclaimed or counterfeit, as some of the review comments suggest?

Also, as I can't see them from the pics... what are the shunt resistors on this board? Will I need to plan on rebuilding the stack to be able to pull 20A through them without fireworks?

mnem
*taking a punt*

It's hard to tell what is or isn't legit. China does a good job of making fakes! This is my second DL24P load tester. The first one arrived with a blown mosfet! The gate was blown on it. So much for ESD protection! I sent it back. The mosfet looked legit...like that really means anything!

The shunts are 5w, R010 or 10 mOhms. I have tons of shunts because of upgrading BMS's. I've touched my shunts under load and they do warm up a little. Replacing them with bigger ones is probably a good idea. They are probably OK for 20 amps as is.

I have to admit...china makes some cheap stuff and often times that means cutting corners...and yet I keep going back for more china junk...LOL!
 

Offline fubgumfaw

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Re: Cheezeball DC Load: DL24P: Pump, or Dump ???
« Reply #24 on: February 24, 2021, 08:48:22 am »
Well...
I looked through my collection of shunts and I had none in 10 mOhms in anything other than 5 watts. I put in an order earlier at Mouser for 10w shunts and IXTH130N20T mosfets. I have half wave bridge diodes so that's not a problem. Copper heat sinks and plate are on the way. I'll be modding this thing soon enough.

This brings me to another application...and yes...of topic.
I don't really use mosfets in their linear region. I mess with motor controllers and BMS's more than anything else and they use mosfets where Rds matters. I need a current limiter. I've been using resistors for this, but mosfets are a better option. I build EV's for myself and for friends. I build my own chargers from PSU's. Charging a battery pack can happen at a much higher rate than the PSU's can deliver. Then they shut down to protect from over load. I've been making a bank of resistors that I can switch in or out that goes inline with the positive output wire from the PSU's. They get pretty warm, but this is OK for wire wound resistors.

The problem is 2 fold:
1. They are fixed resistance and not adjustable. I'd like to do more than just switch them in and out.
2. My charger is made of 8 Meanwell 24v PSU's in series. This lets me select an output voltage that is specific to various pack voltages. I need a resistor bank for each voltage output.

My thinking is a few large mosfets in parallel and running in their linear zone to act as variable resistors so I can limit the current with them like I do with the resistors.
 


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