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.
We talked about MOSFETs for DC loads the other day. I happened across the FDL100N50 today while looking for something else.
With a good enough heatsink (liquid cooled maybe) it has a DC SOA good for at least 1500W within 100A and 500V. Rjc is 0.05 deg C/W so a 25 deg C heatsink actually has some headroom at 1500W. It's pretty linear with about 20mV/a gate sensitivity.
https://www.onsemi.com/pdf/datasheet/fdl100n50f-d.pdf
I happened across the FDL100N50 today while looking for something else.
https://www.onsemi.com/pdf/datasheet/fdl100n50f-d.pdf
I replaced the blown factory mosfet with an HY5110 and it blew almost immediately. I also burnt the trace on the source leg back to the screw terminal and the 2 small shunts. Bigger shunts will be here soon. Mouser has delayed my order twice now. The trace is repaired and beefed up with some solder braid. I'll pull the screw terminal out and add some copper sheet on the current path trace back to that. This ought to hold up now. I'm highly skeptical that the DIY version could handle 1000 watts. I know my mosfet died shorted which created a massive current path across my test LIPO, but still...the traces with no reinforcing and that thin copper and those tiny shunts...not going to happen!
I replaced the blown factory mosfet with an HY5110 and it blew almost immediately. I also burnt the trace on the source leg back to the screw terminal and the 2 small shunts. Bigger shunts will be here soon. Mouser has delayed my order twice now. The trace is repaired and beefed up with some solder braid. I'll pull the screw terminal out and add some copper sheet on the current path trace back to that. This ought to hold up now. I'm highly skeptical that the DIY version could handle 1000 watts. I know my mosfet died shorted which created a massive current path across my test LIPO, but still...the traces with no reinforcing and that thin copper and those tiny shunts...not going to happen!
Do you have the zener in there? If no, you will continue to blow fets
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.Your ideal solution is a proper battery charging circuit, which will take care of a) initial trickle if needed, b) current-limited, but high-current bulk charge, and c) float charge at the end .... all of this tailored to whatever battery chemstry you are using. If you are going to the trouble of monkeying fets to limit current, you should investigate proper battery chargers/charging circuits.
And I can guess that Elon's 250kW superchargers do NOT have resistors or other significantly lossy components in the charge path.... it would just waste too much power.
I replaced the blown factory mosfet with an HY5110 and it blew almost immediately. I also burnt the trace on the source leg back to the screw terminal and the 2 small shunts. Bigger shunts will be here soon. Mouser has delayed my order twice now. The trace is repaired and beefed up with some solder braid. I'll pull the screw terminal out and add some copper sheet on the current path trace back to that. This ought to hold up now. I'm highly skeptical that the DIY version could handle 1000 watts. I know my mosfet died shorted which created a massive current path across my test LIPO, but still...the traces with no reinforcing and that thin copper and those tiny shunts...not going to happen!
Did you see the $200 MOSFET module they recommended for the "DIY 1500W" version...? Obvi not gonna bolt that directly to the PCB; would have to build it offboard with shunts offboard as well as all the power-handling DC busses. This unit would only be used to drive that module.
Did you see the $200 MOSFET module they recommended for the "DIY 1500W" version...? Obvi not gonna bolt that directly to the PCB; would have to build it offboard with shunts offboard as well as all the power-handling DC busses. This unit would only be used to drive that module.
I didn't see this! Can you find it please and post the URL? I'm all for seeing what they did and maybe even copying it. I looked for it on aliexpress...nada....
They both have IRFP260N pass transistors; these appear to be genuine IR brand, but reclaimed parts. So the claims of "shorted transistor new out the box" I've read are not necessarily bogus; these tend to be the most common point of failure in any kind of equipment that uses them for obvious reasons. I recommend removing and testing the FET with your Cheap Chinese Component Tester and doing the recommended crowbar zener and maybe adding a fuse mod before actually applying power to this device.
mnem
Edit of the Edit over a Beer
Enclosure rough out. Not to dimensioned accurately or corners rounded etc but 8 bits of 3mm Acrylic is the plan.
Edit of the Edit over a Beer
Enclosure rough out. Not to dimensioned accurately or corners rounded etc but 8 bits of 3mm Acrylic is the plan.Acrylic is flammable isn't it ?
Burn baby burn.......
Just looking at the "shunts" on my board.
Some serious beefing up work required for any serious application.
So, lesseee...
* Beef up shunts
* Beef up tracks
* Zener
* MOSFET upgrade
.... and I still have to dig out that old CPU cooler.
Have I missed anything....?
Ok Shunts because they are easy 2 parallel 0603 1/8W (most likely) 0.01 shunts. So 1/4W peak for the pair. Take my 10A guesstimate for the tracks and you will likely blow the snot out of the SMD shunts as the pair would handle circa 7A at maximum current
So yep upgrade needed for a start
snip
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!