MSX 84V mosfet blown. Options?

[mrelwood]

I toasted my MSX yesterday, as I described here. One mosfet blown, but seems that the motor cables would only need proper insulation and separation. Mapping my options.

Replacing a single mosfet

The only place I found the mosfet HY5012 for sale was Aliexpress. A month is a horribly long time to wait, without even being sure if a mosfet replacement is enough. I will ask for a faster shipping option though.

Replacing mosfet with a different model

Another option is to replace the mosfets with a different, western model. IXFX300N20X3 has higher performance ratings across the board (200V, 300A, 1250W, original is 125V, 300A, 500W), but a single mosfet costs 22€. For changing the model, I would think that all 12 should be replaced with the same type. That would make the mosfet replacement more expensive than a complete new board. And the board might not even work.

IRFP4468PBF would only cost 4.63€ per mosfet, although a relatively high shipping fee would be added. This is 100V, 290A, 520W. I would think that the 100V MSX uses the same mosfets, which could leave enough headroom for a 100V mosfet on a 84V MSX. Is the voltage headroom enough?

Then there is the IXFH320N10T2 for 9€ a pop, 100V, 320A, 1000W.

For some reason a few Ali sellers mention IRFP2097 and IRFP4368 in the HY5012 sale item title. But they are both only for 75V. (209/300A, 330/520W).

Replacing the whole mainboard

For purchasing a complete control board my options seem to be limited to Chinese sellers as well, since Speedyfeet has sold out, and other stores I found do not sell Gotway or Gotway parts. A message directly to Gotway? Any shops in EU that I've missed?

 

Any other options? Time to buy a new wheel? (No it isn't.)

Edited July 15, 2019 by mrelwood

[Marty Backe]

I know that there are differing opinions, but I would never use a control board that had blown MOSFETs. You just don't know what the collateral damage is or what could have been stressed.

Considering the dire consequences of a subsequent failure, I opt for a replacement control board.

And what I do with my wheels when given the opportunity, is to use zip ties to keep the motor wires from touching even if they get extremely hot. This is one of my ACM's

 

[esaj]

23 hours ago, mrelwood said:

I toasted my MSX yesterday, as I described here. One mosfet blown, but seems that the motor cables would only need proper insulation and separation. Mapping my options.

Replacing a single mosfet

The only place I found the mosfet HY5012 for sale was Aliexpress. A month is a horribly long time to wait, without even being sure if a mosfet replacement is enough. I will ask for a faster shipping option though.

Replacing mosfet with a different model

Another option is to replace the mosfets with a different, western model. IXFX300N20X3 has higher performance ratings across the board (200V, 300A, 1250W, original is 125V, 300A, 500W), but a single mosfet costs 22€. For changing the model, I would think that all 12 should be replaced with the same type. That would make the mosfet replacement more expensive than a complete new board. And the board might not even work.

IRFP4468PBF would only cost 4.63€ per mosfet, although a relatively high shipping fee would be added. This is 100V, 290A, 520W. I would think that the 100V MSX uses the same mosfets, which could leave enough headroom for a 100V mosfet on a 84V MSX. Is the voltage headroom enough?

Then there is the IXFH320N10T2 for 9€ a pop, 100V, 320A, 1000W.

For some reason a few Ali sellers mention IRFP2097 and IRFP4368 in the HY5012 sale item title. But they are both only for 75V. (209/300A, 330/520W).

Don't look too much at the wattage/current absolute maximum -numbers given on the beginning of the datasheets, they're theoretical at best and cannot be attained in reality (at least not without very efficient cooling, like pumped liquid with large external radiator or liquid nitrogen or something, and even maybe not then ).

To use IRFP4468 as an example, here's how they arrive at that 520W number:

Starting point: Ambient temperature at room temperature (usually 25C in datasheets). Case (package) at ambient temperature. Junction-to-case thermal resistance is 0.29C/W (ie. the junction temperature goes up 0.29 celcius above the case temperature per watt of power dissipation). Maximum junction temperature is 175C.

So, assuming the case would magically stay at the same temperature regardless of junction temperature and the heat coming out from the junction wouldn't warm its surroundings, so-called "infinite heatsink-model" where the case temperature never raises, you could theoretically dissipate:

Maximum power = (Maximum junction temperature - Case temperature) / (Junction-to-case thermal resistance)

(175C - 25C) / 0.29C/W = 517.241W

Round that up to 520W for good marketing material. The device would be working right at the theoretical maximum junction temperature limit (175C), and any external heating, or the case heating up, it would likely die. If it can even survive up to (exactly) 175C junction temperature. The thermal resistance between the case and ambient (case-to-sink + sink-to-ambient -thermal resistances) would have to be 0C/W. If the board's getting hot enough to melt solder, the ambient, sink and case temperatures are something totally different than 25C  
Similar "magic" is often used in the calculating the theoretical maximum currents, so you can forget about things like "single mosfet could handle the entire current, it's rated at xxxA!" if just looking at the absolute maximums. I don't know how the peak pulse currents are calculated, heat doesn't move at infinite or "even" light-speed, so with a large current spike, the heat doesn't even have time to conduct away from the junction... They're not outright lying, and all the manufacturers use similar techniques to calculate the maximums (so they look as "good" as the competition), but you can never get to those numbers in the wheel, maybe on a lab bench with very heavy cooling, for a short while. Also, typically the mosfet legs will melt before such figures are reached continuously or in average anyway (that's the "package limited" -value), pulsed they can probably handle high currents for a while, at least if allowed to cool in between.

If you compare the Rds_on -resistances, the list looks like:

• HY5012: 2.9mOhm typical, 3.6mOhm max
• IXFX300N20X3: No typical given, 4mOhm max
• IRFP4468: 2.0mOhm typical, 2.6mOhm max
• IXFH320N10T2: No typical given, 3.5mOhm max

You'd want as low as possible resistance, so as little as possible of power is "wasted" in the mosfet, heating it up.

Another thing to note here is that the IRFP4468 and IXFH320N10T2 are a 100V mosfets, whereas HY5012 is 125V and IXFX300N... is 200V Vds max. Without knowing how high voltage spikes the motor can put out, going lower than the original might be risky. Also, I'm a little bit suspicious of the HY5012-numbers, IXYS and especially International Rectifier (nowadays owned by/part of Infineon) are big brand names in mosfets with long history and breakthroughs in manufacturing technology, a little hard to believe that some never-heard Chinese manufacturer (Hooyi?) is producing mosfets with better specs.

I'd go about selecting in this order: Original (no risk of issues with wrong ratings, since it has worked in the past... well, until it blew ), or if not available/not an option, same or higher Vds_max -voltage as original with same or lower Rds_on -resistance as original. Obviously the same package (TO-247 in this case).

Preferably same'ish gate charge, although someone with an EE -background once said that it likely doesn't matter that much in wheels, since the wheels use (relatively) low switching frequencies and powerful gate drives, but if the gate charging and discharging has been more or less "optimized" for some gate charge (it probably isn't, at least with GW), the gates in the new mosfets might charge/discharge too quickly (lower gate charge, possibly causing gate ringing) or too slowly (higher gate charge, excessive switching losses passing through the linear region on turn-on/turn-off). But probably it's not an issue in reality here.

 

Quote

Replacing the whole mainboard

For purchasing a complete control board my options seem to be limited to Chinese sellers as well, since Speedyfeet has sold out, and other stores I found do not sell Gotway or Gotway parts. A message directly to Gotway? Any shops in EU that I've missed?

 

Any other options? Time to buy a new wheel? (No it isn't.)

Safest bet is to get a whole new board, followed by replacing the mosfet with the same model as the original, followed by using another type of mosfet. Like Marty said above, there is a risk that something else has been damaged along with the failing mosfet, so it's not certain the board will work flawlessly just by replacing the fried fet, although people have replaced fets before and had the wheel working again without an issue.

 

Edited July 16, 2019 by esaj

[mrelwood]

Thank you, @esaj! My knowledge doesn’t allow me to calculate any required ratings for a Mosfet in an EUC, so all I can do is compare the announced values with the original (announced) HY5012 values.

The point about a noname manufacturer bloating specs may well be correct. Although, it seemed easy to find comparable mosfets with comparable prices from other manufacturers, except that they all stop at 100V. So it might be that the western manufacturers are just concentrating on more common requirement ranges.

But @Marty Backe’s point about the trustworthiness of a repaired board has been ringing in my ears the whole day. After all, I often ride long stretches at 45km/h on pavement. It is not an environment where I’m ready to test wether I got all distressed components replaced or not. I will order the new board as soon as I find the fastest supplier. Perhaps a few original Mosfets as well, just so I’d have a spare board.

[evil696]

If you want to sell your wheel i'll be interested.

If you change mosfets, change all, mosfets must be from same production date

[Marty Backe]

1 hour ago, evil696 said:

If you want to sell your wheel i'll be interested.

If you change mosfets, change all, mosfets must be from same production date

Really? This doesn't really make sense. It's not like you are buying carpet, fabric, tiles, etc. where you want the colors to match.

Components are manufactured and tested to a specification. If your components match your application requirements than you're good.

Edited July 17, 2019 by Marty Backe

[mrelwood]

I purchased a new mainboard, and paid $20 for fast DHL shipping. I should receive it early next week.

I will probably order a few original Mosfets, and reconstruct the current one for a spare.

Thanks for all your opinions!

[cgi]

3 hours ago, mrelwood said:

I purchased a new mainboard, and paid $20 for fast DHL shipping. I should receive it early next week.

I will probably order a few original Mosfets, and reconstruct the current one for a spare.

Thanks for all your opinions!

Great to hear you'll be back on one wheel in the not too distant future! Maybe catch you for another ride before the summer's out. Perhaps leave the hill out this time, though .

[US69]

On 7/16/2019 at 9:29 PM, mrelwood said:

Thank you, @esaj! My knowledge doesn’t allow me to calculate any required ratings for a Mosfet in an EUC, so all I can do is compare the announced values with the original (announced) HY5012 values.

The point about a noname manufacturer bloating specs may well be correct. Although, it seemed easy to find comparable mosfets with comparable prices from other manufacturers, except that they all stop at 100V. So it might be that the western manufacturers are just concentrating on more common requirement ranges.

But @Marty Backe’s point about the trustworthiness of a repaired board has been ringing in my ears the whole day. After all, I often ride long stretches at 45km/h on pavement. It is not an environment where I’m ready to test wether I got all distressed components replaced or not. I will order the new board as soon as I find the fastest supplier. Perhaps a few original Mosfets as well, just so I’d have a spare board.

I also can just say:

Dont just change one Mosfet...change the board!

I recently had this conversation with 1radwerkstatt and he explained to me how the mosfets work!

They must work extremly equal, so that not one of them takes the complete load and burn.

If just because of your probably different soldier one mosfet gets another resistance, thats enough for them to run different.

Thats the short version...sorry my english is to bad to write the total explanation.

just dont fiddle with one Mosfet...you shortly will have another burned board again!

Change the board and you are good to go!

Edited July 17, 2019 by US69

[mrelwood]

1 hour ago, cgi said:

Great to hear you'll be back on one wheel in the not too distant future! Maybe catch you for another ride before the summer's out. Perhaps leave the hill out this time, though .

No no no, the game is on! I will separate and secure the motor wires so that I can beat the re-match I’m going to have with the same hill!

What do you mean I’m a sore loser...?

Definitely, another group ride, and new places!

[evil696]

Believe me i know what i'm sayng, you think that mosfets are the same but they dont, if you do battery pack you take all batteries from one production cause they are mostly the same, with mosfets is the same thing, mosfets with different part of production have nominal (datasheet) paramaters but they dont really the same.

My friend, much older than me, tells me if you change mosfets change all with same part of production and i believe him.

Mosfets are chep in china.

[Marty Backe]

30 minutes ago, evil696 said:

Believe me i know what i'm sayng, you think that mosfets are the same but they dont, if you do battery pack you take all batteries from one production cause they are mostly the same, with mosfets is the same thing, mosfets with different part of production have nominal (datasheet) paramaters but they dont really the same.

My friend, much older than me, tells me if you change mosfets change all with same part of production and i believe him.

Mosfets are chep in china.

Well, of course every component is different, but if they all meet the datasheet spec, than they are the same as far as the circuit design is concerned. If your hardware design is dependent on "same lot" components, than it's a poorly designed circuit.

When you say "i know what i'm saying", what you really mean is that you believe your friend knows what he's saying 

[mrelwood]

I don’t doubt the argument that Mosfets best to be from the same lot. Regular resistors for example have a tolerance of +-10% or even +-20% (carbon resistor). When building guitar effects using J201 fets, one has to buy a bunch and screen them oneself due to huge tolerances. I have no idea what the power mosfet tolerances are, but no reason to doubt that they can be notable as well. 

[evil696]

Im electronic with about 15 years of experience, i repair EUC motherboards. And do you know why mosfets burns... cause they work in high end parameters, when you connect two mosfets parallel with different productions there will be higher propability that this pair will burn faster than the same production, cause RDS will be a little bit different and heat wont be the same on bouth mosfets, second thing is to electric separate all mosfets but they should be thermally connected as close as possible. In your case i will propably take out all mosfets and connect laboratory power supply, power consumption will tell you if any logical chip was burned if you think to change mosfets you can use IRF100B201 aliexpress.com $3.47 for 5 pcs

[evil696]

I know that propably noone will help me but good to try i'm looking for dumped firmware from inmotion V10 2 chips STM32F103 if anyone will share i'll be gratfull.

[mrelwood]

44 minutes ago, evil696 said:

you can use IRF100B201

The mosfet you mentioned is in a smaller TO-220 package, and only rated for 100V and 192A, and also the resistance is a bit higher. The original HY5012 is in TO-247 package, and rated at 125V and 300A. While I don’t have the knowledge to doubt, valuate or even compare the datasheets very closely, I wouldn’t have the guts to replace the mosfets with those IRF ones.

[evil696]

you right about mosfets i'd look on picture from second post and these mosfets are TO-220 sorry my bet.

[evil696]

Can you send picture of your mainboard and battery.

[evil696]

Ok i check on internet how this MB look like.

You are right TO-247, do you have any option to connect mainboard to laboratory power supply?

If you have remove all mosfets, connect Lab PSU set current to 200ma and start rise voltage from 10 to 60v look for current consuption and cherck by your hand is there any chip heats up, if your PSU doesnt support 60v output it wont be problem, my have 31v output and its enaugh to chceck motherboard, after mosfets burn there is some options first is that only mosfet is damadge, second mosfet driver is demadge (this 8 pin element between 2 ceramic capacitors there is 3 of them one for a coil) and last worst option microcontroller burned if you have this motherboard is totally dead cause microcontroller have code protection and nobody get this firmware even from working wheel and i dont think that gotway will share it.

[Marty Backe]

5 hours ago, evil696 said:

Im electronic with about 15 years of experience, i repair EUC motherboards. And do you know why mosfets burns... cause they work in high end parameters, when you connect two mosfets parallel with different productions there will be higher propability that this pair will burn faster than the same production, cause RDS will be a little bit different and heat wont be the same on bouth mosfets, second thing is to electric separate all mosfets but they should be thermally connected as close as possible. In your case i will propably take out all mosfets and connect laboratory power supply, power consumption will tell you if any logical chip was burned if you think to change mosfets you can use IRF100B201 aliexpress.com $3.47 for 5 pcs

 

5 hours ago, mrelwood said:

I don’t doubt the argument that Mosfets best to be from the same lot. Regular resistors for example have a tolerance of +-10% or even +-20% (carbon resistor). When building guitar effects using J201 fets, one has to buy a bunch and screen them oneself due to huge tolerances. I have no idea what the power mosfet tolerances are, but no reason to doubt that they can be notable as well. 

All I'm saying is requiring components (MOSFETs, resistors, etc) from the same lot is a consequence of an inferior circuit design. It's a "cheap" design.

[mrelwood]

1 hour ago, Marty Backe said:

 

All I'm saying is requiring components (MOSFETs, resistors, etc) from the same lot is a consequence of an inferior circuit design. It's a "cheap" design.

I wouldn’t expect anything less from Gotway... 

[Hansolo]

After changing the mosfet on a mother board for my MS3 (burning starting on a slope...), when I connecting the battery:

Connector XT150:

 

[Marty Backe]

11 minutes ago, Hansolo said:

After changing the mosfet on a mother board for my MS3 (burning starting on a slope...), when I connecting the battery:

Connector XT150:

 

I've never understood the exact sequence that causes this to happen to some people. I've never experienced anything but the smallest of sparks.

[Patton250]

 It’s always nice to read about a product frying it self especially when you just receive the exact same product. 

[Marty Backe]

12 minutes ago, Patton250 said:

 It’s always nice to read about a product frying it self especially when you just receive the exact same product. 

Did you just receive an MSuper V3? A 2-year old wheel.