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SuperSport

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Yeah, I was thinking the other day that for those who are in extreme weather conditions, that this might be a good idea to incorporate some how.  I've messed with them a little bit, and they are quite effective at Heating OR Cooling.

In the Winter, warm the battery, and in the summer, cool the Mosfets by cooling the heatsink.

https://www.adafruit.com/products/1331

Peltier.jpg.61145a7dca838e98e3958d4bcc10

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4 minutes ago, SuperSport said:

Yeah, I was thinking the other day that for those who are in extreme weather conditions, that this might be a good idea to incorporate some how.  I've messed with them a little bit, and they are quite effective at Heating OR Cooling.

https://www.adafruit.com/products/1331

Peltier.jpg.61145a7dca838e98e3958d4bcc10

 

Never worked with Peltier-elements, does it switch the sides which get hot and cold if you reverse the polarity? I'm more worried of battery packs getting too cold during cold weather than overheating my wheel (although since I don't think Firewheel has any temperature sensor, I don't know how hot it has been running during the very few hot days we had in the summer ;)).

As a totally off-topic sidenote, I finally got my MPU6050-breakout boards today, yay! And a bunch of other stuff that has entered the country over a month ago, looks like the postal service took its sweet time to sort out the shipments that arrived during the strike (I've already received a lots and lots of other packets ordered much later, these were ordered almost 2 months ago). Time to get cracking on that self-balancing robot...

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10 minutes ago, esaj said:

Never worked with Peltier-elements, does it switch the sides which get hot and cold if you reverse the polarity?

Yes, that's exactly what they do, switch polarity to either.  I wonder if there would be a way to connect the cold side to the Mosfets Heatsink Permanently, and then use the hot side to warm the batteries, thus doing dual duty.

Using a Cooling/Heating tube coming from THIS heatsink and fan, then run it across to the batteries.

PeltierFan.jpg.3a9ef0d45577d4e9fd4c5f002

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5 minutes ago, SuperSport said:

Yes, that's exactly what they do, switch polarity to either.  I wonder if there would be a way to connect the cold side to the Mosfets Heatsink Permanently, and then use the hot side to warm the batteries, thus doing dual duty.

Not sure, but I think that's one single unit, you probably can't separate the hot and cold sides? Personally, I'd use an H-bridge to switch the polarity as needed to do heating/cooling, maybe with thermostat control with hysteresis?

EDIT: Just now saw your edit, yeah, running a separate cooling circuit (with liquid or heatpipes or whatever) would probably work.

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13 minutes ago, esaj said:

Not sure, but I think that's one single unit, you probably can't separate the hot and cold sides? Personally, I'd use an H-bridge to switch the polarity as needed to do heating/cooling, maybe with thermostat control with hysteresis?

You cannot separate sides, but when you switch polarity, the opposite side cools and warms.  I've done it.  You HAVE to use a heat sink, otherwise it just melts down (I've also done that).  Look at my Edited post above.  Using the fan, you could heat batteries AND cool Mosfets.

Those Miniature Refrigerator Heaters use these.  Just turn the cable over for hot or cold.

Edit: Not sure about Battery Consumption though.  I know I don't want to leave my fridge plugged in overnight in my car, or my battery might be dead next morning.

If you lay this element on the table and plug it in, one side will give you a FREEZE burn, and the other side will give you a HEAT burn.  Both can blister.  It's amazing to see them work, as one side literally has ice on it, and the other is burning things.  SO Small, but SO effective!  VERY Cheap, and they come in different voltages too.

Remember, it HAS to have a heat sink or it melts down.  Because I figure you are now going to grab one of these...

In the small fridge I have, they heat sink both sides and reverse polarity on both the device and the fan.  When heating, they blow air IN across the unit.  When cooling, they blow air OUT across the unit.

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I might grab one of those out of interest, but I wouldn't (probably) use it for the battery heating, instead I'd opt for a simple thermostat & heat resistor-wire (the kind that's sold in rolls and has specific resistance per meter).

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21 minutes ago, esaj said:

I might grab one of those out of interest, but I wouldn't (probably) use it for the battery heating, instead I'd opt for a simple thermostat & heat resistor-wire (the kind that's sold in rolls and has specific resistance per meter).

Ah, a MUCH better idea.  That's the stuff in my wife's cars Heated Seats, and in our heated Motorcycle jackets and gloves?

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3 minutes ago, SuperSport said:

Ah, a MUCH better idea.  That's the stuff in my wife's cars Heated Seats, and in our heated Motorcycle jackets and gloves?

Not sure, could be, never torn down a car seat to see what's there ;)

I was thinking something like this:  https://en.wikipedia.org/wiki/Kanthal  (there are multiple different resistances to choose from domestically) +  http://www.aliexpress.com/item/New-12V-10A-Digital-LCD-Temperature-Regulator-Controller-PCB-Board-Thermostat-Sensor-hot-selling/32579022271.html or http://www.aliexpress.com/item/WX-101W-thermostat-temperature-control-switch-board-digital-temperature-controller/32460363902.html

With "suitable" front resistor and/or suitable wire resistance, it shouldn't get too hot yet work as a heating element around the batteries.

But I think I'll move this conversation to it's own topic, as we're getting really off-topic from Ninebot One E power reduction... ;)

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Bad idea, you would be adding about 20 watts of heat when the design has no real way to remove heat in the first place. I have an arm development board that uses 4-8 watts. It came with a small cooler, maybe 20 or 30 grams and a noisy high speed fan. I replaced it with a 500gram cooler off a desktop with 6 heat pipes but removed the 120mm fan, it can barely keep the CPU under 100c with passive cooling and cools less than a tiny heatsink with a fan.

The best way to cool EUCs would be to have a small lightwight heatsink with a large surface area and a fan, you would also need a vent for hot air to escape and another to draw cool air inside.

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A funny piece of trivia, not really *that* related to this topic, but close enough, about the temperature measurement of the wheels (or at least Gotway and Kingsong):

I've been playing around with the MPU6050 (a gyroscope/accelerometer -sensor used in most wheels). Reading through examples etc., I found out that the chip actually also has a temperature sensor built-in. Seeing the example code, it seemed somehow familiar:

Serial.print(" | Tmp = "); Serial.print(Tmp/340.00+36.53);  //equation for temperature in degrees C from datasheet

You know why? That's exactly the same equation used in King Song and Gotway protocols to read the temperature value from the data. So I believe they actually are reading the temperature from the MPU6050-chip, which, depending on board layout, could actually be pretty far from the really hot stuff (mosfets, mostly). 

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10 minutes ago, Colestien said:

@esaj did you see the Control board on Jason's video from CES?  Next upgrade...fan on heat sink! 

Yeah, I saw it. It should even out the temperature at least somewhat, but unless they exhaust the hot air somehow, it won't totally prevent overheating (especially in hot weather). The heat will (eventually) dissipate even through plastics, but probably at a slow rate and might still not be enough to cool it faster than the heat builds up. The best options from my point of view would be to either have the heatsink protrude through the casing (and sealed around it so no water gets in) either into the inside (where air flow from the turning tire would cool it) or outside, or have some kind of air exhaust / intake vents (but they would have to be positioned / shaped so that no water can get in).

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40 minutes ago, esaj said:

The best options from my point of view would be to either have the heatsink protrude through the casing (and sealed around it so no water gets in) either into the inside (where air flow from the turning tire would cool it) or outside, or have some kind of air exhaust / intake vents (but they would have to be positioned / shaped so that no water can get in).

On our Land Rovers, we had a lot of Snorkel Designs that would lend themselves well to these as long as they are kept upright in deep water.

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I have been looking a bit into the "refrigeration" of the Mos FET in the NineBot One E+. As I see it there are two easy modifications :

- Substitute the aluminium plate with one with fins at the wheel side. That would reduce the heat transfer resistance to the exterior.

- Better the resistance from the MOSFET to the plate. As I see it is not very good. In some models is just a sheet of aluminium. In another it is a heat sink that sins to the interior of the box. Probably substituting it with a block of aluminium may better.

A more dificult modification would be to put the MOSFET in direct contact with the plate.

As I live in Spain and in summer will be very hot this is an interesting point. What do you think?

Not a problem here, but for you in Finland two tubes between main board box and battery box and a small fan or turbine for forcing the air may be a good idea (must look for space).

 

 

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1 hour ago, Paco Gorina said:

I have been looking a bit into the "refrigeration" of the Mos FET in the NineBot One E+. As I see it there are two easy modifications :

- Substitute the aluminium plate with one with fins at the wheel side. That would reduce the heat transfer resistance to the exterior.

As passive cooling, this would probably be the most efficient(?)

Quote

- Better the resistance from the MOSFET to the plate. As I see it is not very good. In some models is just a sheet of aluminium. In another it is a heat sink that sins to the interior of the box. Probably substituting it with a block of aluminium may better.

A more dificult modification would be to put the MOSFET in direct contact with the plate.

You cannot make a direct metal-to-metal connection here, as the metal-"back" of the mosfet is actually the drain-pin (at least in most mosfets). You'd be shorting together the drains of the high- and low-side mosfets and low-sides would short circuit the moment they're opened (direct connection from VCC to GND, only resisted by the internal resistance of the mosfet and the batteries, which is probably below 1ohm, all power is dissipated by the mosfet). They need to be electrically insulated from the plate.

Quote

As I live in Spain and in summer will be very hot this is an interesting point. What do you think?

Not a problem here, but for you in Finland two tubes between main board box and battery box and a small fan or turbine for forcing the air may be a good idea (must look for space).

Not a bad idea, but I doubt it would be enough to keep the batteries warm at the winter temperatures here (-10C...-30C or sometimes colder) ;)

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18 hours ago, esaj said:

As passive cooling, this would probably be the most efficient(?)

You cannot make a direct metal-to-metal connection here, as the metal-"back" of the mosfet is actually the drain-pin (at least in most mosfets). You'd be shorting together the drains of the high- and low-side mosfets and low-sides would short circuit the moment they're opened (direct connection from VCC to GND, only resisted by the internal resistance of the mosfet and the batteries, which is probably below 1ohm, all power is dissipated by the mosfet). They need to be electrically insulated from the plate.

Not a bad idea, but I doubt it would be enough to keep the batteries warm at the winter temperatures here (-10C...-30C or sometimes colder) ;)

If I remember 40 years ago we had same problem with 2N3055 transistors and was solved with a mica between the transistor and the aluminium sink. Usually put the silicone between transistor and mica sheet and between mica sheet and sink.

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