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MOSFET Heatsink Design Idea Totally Tubular!


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Okay it seems like heat is a big issue with some control boards.  So I'm thinking why not mould a channel into the shell where a rectangular or square (or whatever shape you want) tube of aluminum can seat into.  It extends to the exterior of the wheel on both sides where there is a little mesh grill to prevent bugs from getting in.  The MOSFETS can then be attached to this tube that runs through the area so when the user is riding, air rushes through and helps cool everything down.  Add in some heat dissipating fins inside if needed, but the main feature is that the air rushing through will help carry away the heat while keeping water out of the control board area.

It's always nice to ride as there's this constant wind in your face as you glide by.  Why not tap that air and make use of it?  Instead of adding a fan inside a closed, weather-proofed chamber, through motion we can BE THE FAN!

As an aside, there also has to be an easy way to design a circuit to somehow not shutdown a fully charged battery if going down a hill?  How does Tesla do it?  Do Tesla drivers fear a full charge and then go oh no I have to drive down that really steep hill?  There's gotta be a simple solution somewhere.  How about shunting the excess power to some sort of fan in that case or to help charge an accessory battery on the side?  I know it's been mentioned before I think, but why don't they incorporate this safety feature?

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2 hours ago, HunkaHunkaBurningLove said:

Okay it seems like heat is a big issue with some control boards.  So I'm thinking why not mould a channel into the shell where a rectangular or square (or whatever shape you want) tube of aluminum can seat into.  It extends to the exterior of the wheel on both sides where there is a little mesh grill to prevent bugs from getting in.  The MOSFETS can then be attached to this tube that runs through the area so when the user is riding, air rushes through and helps cool everything down.  Add in some heat dissipating fins inside if needed, but the main feature is that the air rushing through will help carry away the heat while keeping water out of the control board area.

It's always nice to ride as there's this constant wind in your face as you glide by.  Why not tap that air and make use of it?  Instead of adding a fan inside a closed, weather-proofed chamber, through motion we can BE THE FAN!

As an aside, there also has to be an easy way to design a circuit to somehow not shutdown a fully charged battery if going down a hill?  How does Tesla do it?  Do Tesla drivers fear a full charge and then go oh no I have to drive down that really steep hill?  There's gotta be a simple solution somewhere.  How about shunting the excess power to some sort of fan in that case or to help charge an accessory battery on the side?  I know it's been mentioned before I think, but why don't they incorporate this safety feature?

Electric cars switch off regen when they are charged and rely on good ole brakes. Just don't go down a big hill when the battery is fulled charged !  I guess big hill strategy with a full battery would be to go down a bit and up the hill again to create some space or maybe a series of circles all the way down.

Jer

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Heatpipes are the best solution to this. They are basically a passive water cooler, you can mount a aluminium heatsink somewhere that gets airflow and connect it to the mosfets via a heatpipe that is only 5mm in diameter, meaning sealing it is very easy.

Inside heatpipes is a sintered copper foam and a vacuum with a coolant liquid. Due to the low pressure the liquid boils at low temperatures and travels away from the heat to the cool end where it returns to liquid form and is absorbed back into the copper foam. They are immune to gravity and transport heat better than any solid metal.

The only real limitation is you must bend the pipe into shape before creating the vacuum and adding the coolant.

Asus_P5K3_CPUArea1.jpg

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I had thought of adding fins to the wheel rim to help promote air flow, I wonder if it might be better to have them mounted at an angle to act more like a fan?

I have ordered computer cpu fans and when they arrive I will open my beloved KS14C and attack the over heat issue by doing 3 things.

Adding thin vertical alu fins to heat sink for more surface area.

Opening case top with square openings to fit fans if needed, and testing that maybe by just letting the top of the motherboard breath that this will help enough?

Attaching "fan like fins" to the rim with special glue and if works tig welding alu ones.

UKJ

 

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3 hours ago, HunkaHunkaBurningLove said:

Okay it seems like heat is a big issue with some control boards.  So I'm thinking why not mould a channel into the shell where a rectangular or square (or whatever shape you want) tube of aluminum can seat into.  It extends to the exterior of the wheel on both sides where there is a little mesh grill to prevent bugs from getting in.  The MOSFETS can then be attached to this tube that runs through the area so when the user is riding, air rushes through and helps cool everything down.  Add in some heat dissipating fins inside if needed, but the main feature is that the air rushing through will help carry away the heat while keeping water out of the control board area.

It's always nice to ride as there's this constant wind in your face as you glide by.  Why not tap that air and make use of it?  Instead of adding a fan inside a closed, weather-proofed chamber, through motion we can BE THE FAN!

Like a RAM Air Intake - If the circuit overheats one was driving to slow! ;)

Quote

As an aside, there also has to be an easy way to design a circuit to somehow not shutdown a fully charged battery if going down a hill?  How does Tesla do it?  Do Tesla drivers fear a full charge and then go oh no I have to drive down that really steep hill?  There's gotta be a simple solution somewhere.  How about shunting the excess power to some sort of fan in that case or to help charge an accessory battery on the side?  I know it's been mentioned before I think, but why don't they incorporate this safety feature?

Like @jerstated they have normal brakes and additionaly they have no problem to mount big power resistors to dissipate breaking power. 

A fan capable of dissipating breaking energy would be a new form of propulsion.

2 hours ago, EUC Extreme said:

Such works very well, and is definitely waterproof.

...

Great construction - i like it!

9 minutes ago, UKJ said:

I had thought of adding fins to the wheel rim to help promote air flow, I wonder if it might be better to have them mounted at an angle to act more like a fan?

The KS14C mainboard has access to the inner wheel casing with the heatsink, so this measure could improve cooling?

9 minutes ago, UKJ said:

I have ordered computer cpu fans and when they arrive I will open my beloved KS14C and attack the over heat issue by doing 3 things.

Adding thin vertical alu fins to heat sink for more surface area.

Opening case top with square openings to fit fans if needed, and testing that maybe by just letting the top of the motherboard breath that this will help enough?

Enabling convection is always a great idea - and often sufficient for nice cooling! If not the next step is a fan or your wheel venting mod...

9 minutes ago, UKJ said:

Attaching "fan like fins" to the rim with special glue and if works tig welding alu ones.

Imho you just should be careful that by some stones/pebbles/or whatever the "fan like fins" cannot be torn away and somehow be thrown out of the wheel casing to finally stick in someone... especially the alu ones...

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12 hours ago, jer said:

Electric cars switch off regen when they are charged and rely on good ole brakes. Just don't go down a big hill when the battery is fulled charged !  I guess big hill strategy with a full battery would be to go down a bit and up the hill again to create some space or maybe a series of circles all the way down

My first-generation Prius tries to maintain an 80% charge level in normal operation, so it has a good sized buffer for storing brake energy. Normally when you're going downhill without brakes you are just coasting. However there is a "B" setting on the transmission selector that will switch into regen braking for downhill runs. I have never gotten to 100% charge in B mode but I suspect it would just switch back to coasting and you'd need to apply more brakes.

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It has not been the problem of dirt.

13 hours ago, HunkaHunkaBurningLove said:

Do you find that dirt and mud get stuck in the fins over time?  How do you seal up the sides?

It has not been the problem of dirt.

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Heat is only part of the problem, the other part of the problem that relates to heat but it is harder to solve it is current. When driving flat or small inclines very little current it is used and it is a matter of having proper cooling.

The real problem which is more than just cooling are inclines over 14 degrees or 25% grade for riders over 100kg, the current being draw is over 30A, most high end boards gotway, kingsong, microworks, appear to be rated at 30A, by exceeding this amount of current even with proper cooling the board will get damaged and it is a safety hazard once the board it is damaged it is possible to faceplant.

Under ideal conditions it would be great to have a board rated for 60A or more, then it becomes a matter of only cooling, but such a board currently does not exist.

One untested idea is to run 2 control boards of the same type in parallel, this way the current is divided among the 2 boards with each board less likely to overheat, some ventilation would still be needed. Both boards could be calibrated so they run in perfect synchronization with each other.

This is the cooling fix for a ks18a, I am planning on adding tiny fans.

High end boards should not be limited to 6 MOSFETs, they should have 18 at least even if they would cost a little more safety on a EUC it is important.

IMG_20160508_180935.jpg

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23 minutes ago, checho said:

High end boards should not be limited to 6 MOSFETs, they should have 18 at least even if they would cost a little more safety on a EUC it is important.

Adding more mosfets doesn't make it any cooler, it just spreads the heat across more mosfets. The heatsinks in most EUC aren't heatsinks, they're heat capacitors, they have almost no way to disperse heat and just absorb it hopefully slowly enough that the battery runs out before the heatsink is totally saturated.

This is what a 175watt heatsink looks like, EUC shouldn't be putting out much more than 30watts of heat while running the motor at 2kw. It's not even hard to cool this with a proper heatsink, even in hot 40c climates.

 

15a.jpg

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Adding more MOSFETs does not make it run cooler, but it reduces the current that goes through each MOSFET, if too much current goes through a MOSFET it will get damaged regardless of the temperature, doubling the MOSFETs you double the current that the board can handle, and this is very important for heavy riders on steep hills.

You would still need to disipate the heat with fans/heats sinks but you would not be running more current over the MOSFETs than they are rated for.

In the ebike world you have control boards with 18 MOSFETs, and none of the 6 MOSFETs boards even with proper cooling with match the power that an 18 MOSFET board can handle, the same would be true for EUCs today, such boards currently do not exist it is a matter of time before they do exist.

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You can build a 67V 200A controller with 6 fets that cost $36, it's just a matter of designing cooling properly. You have 3cm x 3cm computer chips producing over 200watts of heat, you just have to transport the heat away from the semiconductor rapidly. The reason others have so many fets is they want to cool them passively using a chunk of copper or aluminium 

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I thought of something mechanical in order to let the air flow trough the mosfet's dissipator . It's just an idea, as my entry level EUC won't need (I think) an addictional airflow. The idea would be to perform some holes in the case as shown in the picture , may a front fender (drawn in black) avoiding part of the possible rain to enter ,
have an inner tube taking the airflow in contact of dissipator while a different exhaust tube will collect (in case) the heavier particel (like water) down to a bottom hole which will make them exit..

 

Airflow.jpg

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I like your designs Polpus.  I would still be concerned about say water ingress while say riding in the rain just like they did on the Amazing Race.  If a rider were going past a puddle, and say a car zooms by sending a wave of water splashing on the EUC, some might make it onto the control board.  I think it's better to somehow make the control board area water-tight while air passes by cooling a tunnel of aluminum to help draw the heat away.  That way the whole EUC can fall into a puddle of water or be submerged with minimal fear if both the battery and control board (plus buttons/charger port) are weather proofed.  For something meant to be used outdoors, it should be ready for all sorts of weather conditions. 

Or maybe redesign your plan to have an air chamber with an aluminum divider that pipes the air up and over the control board area which is completely separated by the wet side so air / water can get in, air exits up and over, and water drains down by gravity.  In the drawing below, the grey area could be all heatsink with fins and the yellow circles exit holes.  The grey heat sink areas could be sealed so no water passes to the green area.  A tube might be easier to seal up though.  One other concern might be mildew buildup inside if water doesn't dry out completely.

airwater.jpg

I think Vee's fin cooler next to the wheel is likely the best option, but maybe a simple tube pass through might provide enough cooling air for most conditions.  The tube idea could also work with a liquid coolant and a small radiator as well instead of being just air-cooled for say riding in the desert where it's hot like 40 C outside in places like Abu Dhabi.

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Yeah Hunka you go further my idea, loved it . Mine was just a quick idea and yes you devoloped it correctly .

I don't know wether I'd put a fan (always ON ? Play with electronics and thermocouple to have it ON only when it needs?)

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@OliverH it would need an air chamber where to place the motherboard as proposed by Hunka , that way would be efficient I think and the two part (i.e. electronics and ''free space'') would be separeted and watertight !

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1 minute ago, Polpus said:

@OliverH it would need an air chamber where to place the motherboard as proposed by Hunka , that way would be efficient I think and the two part (i.e. electronics and ''free space'') would be separeted and watertight !

Maybe modify your idea with a foil like Sympatex, a membrane working as a water blocker and also allows to "breath".

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On 9.5.2016 at 8:00 AM, checho said:

Heat is only part of the problem, the other part of the problem that relates to heat but it is harder to solve it is current. When driving flat or small inclines very little current it is used and it is a matter of having proper cooling.

The real problem which is more than just cooling are inclines over 14 degrees or 25% grade for riders over 100kg, the current being draw is over 30A, most high end boards gotway, kingsong, microworks, appear to be rated at 30A, by exceeding this amount of current even with proper cooling the board will get damaged and it is a safety hazard once the board it is damaged it is possible to faceplant.

Under ideal conditions it would be great to have a board rated for 60A or more, then it becomes a matter of only cooling, but such a board currently does not exist.

One untested idea is to run 2 control boards of the same type in parallel, this way the current is divided among the 2 boards with each board less likely to overheat, some ventilation would still be needed. Both boards could be calibrated so they run in perfect synchronization with each other.

This is the cooling fix for a ks18a, I am planning on adding tiny fans.

High end boards should not be limited to 6 MOSFETs, they should have 18 at least even if they would cost a little more safety on a EUC it is important.

IMG_20160508_180935.jpg

What version of the KS18 A? 800W or 1100 W (motor labeled wit 1200 W)? Do you've big problems with heat? There was one report 1-2 weeks ago where someone states no problem at all. So the problem isn't fixed at Kingsong?

You've bought a second main board for testing/ modifying?

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I have the ks18a 1100w motor labeled 1200w.

Yes the overheating problem does exist and it  can be reproduced.I weight 110kg  and when going up steep hills over 10 degrees, the EUC begins to overheat and as you go up the hill the temperature keeps increasing after 10 minutes it will be above 60 degrees C. 

This problem does not occur for light weight riders, or heavy riders on mostly flat surfaces, it is even posible to ride several miles without overheating on flat or small hills, I rode my ks for about 2 hours in city driving mostly flat and it did not overheat.

But only 10 minutes on steep hills and overheating occurs quickly, a hill that makes you draw over 50A on the android app is a steep hill.

On steep hills the android app registers between 50 to 55 Amps, when you draw that much power overheating does occur. The real Amps are much lower than the Amps reported by the android app, sometime in the near future  I will find out how much is 50A on the app to real Amps.

After overheating the board got damaged,  it works only for a few minutes and then does strange things like spinning the wheel non stop, or stop balancing, I had a nasty face plant when it stopped balancing, it was my fault I should have stopped riding the first time it stopped balancing, but afterwards it seemed to be working only to stop balancing a few minutes later.

The board with the heat sinks is my modification to improve the cooling, next part of the plan is to install 1 or 2 fans and have air circulation.

King Song were very nice and they replaced the bad board under guarantee.

The reason others do not report the overheating is that they are light weight or do not ride on steep hills for more than a few minutes.

But with a hill of 10 deegrees or more, and a load of 110kg the overheating does happen, on a warm day.

The new board is working great but I have been avoiding steep hills to prevent the overheating. 

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19 hours ago, checho said:

I have the ks18a 1100w motor labeled 1200w.

Yes the overheating problem does exist and it  can be reproduced.I weight 110kg  and when going up steep hills over 10 degrees, the EUC begins to overheat and as you go up the hill the temperature keeps increasing after 10 minutes it will be above 60 degrees C. 

This problem does not occur for light weight riders, or heavy riders on mostly flat surfaces, it is even posible to ride several miles without overheating on flat or small hills, I rode my ks for about 2 hours in city driving mostly flat and it did not overheat.

But only 10 minutes on steep hills and overheating occurs quickly, a hill that makes you draw over 50A on the android app is a steep hill.

On steep hills the android app registers between 50 to 55 Amps, when you draw that much power overheating does occur. The real Amps are much lower than the Amps reported by the android app, sometime in the near future  I will find out how much is 50A on the app to real Amps.

After overheating the board got damaged,  it works only for a few minutes and then does strange things like spinning the wheel non stop, or stop balancing, I had a nasty face plant when it stopped balancing, it was my fault I should have stopped riding the first time it stopped balancing, but afterwards it seemed to be working only to stop balancing a few minutes later.

The board with the heat sinks is my modification to improve the cooling, next part of the plan is to install 1 or 2 fans and have air circulation.

King Song were very nice and they replaced the bad board under guarantee.

The reason others do not report the overheating is that they are light weight or do not ride on steep hills for more than a few minutes.

But with a hill of 10 deegrees or more, and a load of 110kg the overheating does happen, on a warm day.

The new board is working great but I have been avoiding steep hills to prevent the overheating. 

That's the same I realized with the old KS18 500 W. 

You should see around 30 A with real measuring.

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