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Off Topic: Mechanical/Electronics & Cold Weather
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* April 28, 2018, 02:53:18 PM
I need to get feedback from users of dc motors, electronics including sensors from people in north america, europe and antartica/artic regions. What effect do these colder climate have on the operational functions of:
DC electric motors ( eg: 12, 24 and 36 volt )
electronics ( modules, lcd displays, led's and other )
electronic standalone sensors ( thermo resistors )
SLA ( sealed lead acid ) and lithium ion batteries 

What effect doe the cold climate have on their operational functionality, eg:
Do DC motors freeze up and stop working?
Do Electronic modules fail or are their display screens fail or display just garbage characters
Do sensors function in freezing conditions?
Do SLA or Lithium ion bateries fault in any way due to the cold?

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


* April 28, 2018, 09:15:09 PM
#1
Hi, Daz.

I have lived in Alaska for 25 years, but I am in Southcentral so it does not get very cold here, usually winter temperatures at my house no colder than -20 Deg F.  I worked in the electric motor and generator industry, mostly for the oil companies.  I know about large motors more than small motors, but many factors will be the same.

The problem with electric motors in cold climates is lubrication of the bearings, whether they are sleeve bearings or ball bearings.  The windings are not affected in a significant way due to the cold temperature.  Brushes on DC motors are fine.  There is a temperature coefficient of resistance for copper, but it is not a problem with standard motors.  As an example, when you start your car at -20 F, the fan motor (12VDC) may squeal due to the bearing being "dry" as the lubricant is not flowing through the bearing. 

A car may have most or all of the types of components you are asking about.  A car can be started at -30 F (it may clatter a bit) and everything will work, but it is hard on the engine.  The electronic ignition will work and the heater motor and window motors will work, and the stereo.  In the cold climates, cars and trucks are typically equipped with engine block heaters so the engine will have adequate lubrication on startup.  Some people have heaters on their batteries as well, but that is rare, in my experience.  Everything else will work okay.

Regarding electronic components and modules, these should have ratings available documenting the allowable operating temperature range.  Manufacturers provide data sheets for sensors which show the allowable operating temperatures and temperature performance curves, where appropriate.  You may also be able to talk to engineers at the factory.

Anyway, in general things will work, but you will still need to verify that specific components will operate in the environment you are designing for.

John Earl

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* April 29, 2018, 02:24:34 AM
#2
John that was really useful information you've posted. I do know that say in Alaska it gets damn cold there so what is normally the coldest temp that you might experience?

What occurs with grease lubricant in those extremes, do they turn to a solid and inhibit rotation of bearings?

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


April 29, 2018, 03:03:44 AM
#3
Daz,

as John mentioned, lubricants can be a problem in very cold temps.
I spent some time working in the Antarctic (down to -40° C), and usually items were preheated or kept warm prior to use.

Batteries did not work in those sort of temperatures, as the voltage dropped significantly.
Again, preheating helped.
Today, lithium-ion batteries are a great improvement in extremely low temperatures.
However, charging rates must be reduced if these batteries are to survive.

I hope this helps.

Regards Tim

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* April 29, 2018, 07:13:11 AM
#4
My experience is with Li- ion batteries in power tools and Li-poly batteries in radio control planes.  Tools with Li-ion left overnight in a truck in cold and sub-freezing temperatures have less power and seem to  lose charge faster until they warm up. Brushless motors running in airplanes on Li-poly batteries seem to develop less power when cold. No actual data to back this up, just observation.

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* April 29, 2018, 01:57:23 PM
#5
Tim & extra230 thats also useful info on the batteries. So lithium ion will be used on all designs under cold weather. Heaters thats upto the evaluation team depending on location if they work successfully then great stuff.

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


* April 29, 2018, 03:14:05 PM
#6
Daz,

In very cold conditions the grease becomes stiff and does not allow oil to flow from it.  It is a understood that grease is a lubricant, which is true in a way, but it is more accurate to think of the base of a grease as a sponge which holds oil.  The base is the viscous, pasty part of the grease and is not the lubricant, the oil held by this material is the lubricant.  The grease lays against the bearing and oil flows from the grease very slowly to lubricate the bearing.  In very cold conditions, the base of the grease becomes hard and the oil is trapped inside.  Special low temperatures greases are formulated so they will remain soft and release the oil at very cold temperatures.  Different formulations of grease will have different bases and also different oils.

Electric motors and generators which have sleeve bearings, and are in cold environments, will have heaters in the oil reservoirs.  Motors and generators with ball bearings are lubricated with low temperature grease and are not heated.

These machines will start at very cold temperatures but the problem is that damage can occur to the bearings if adequate lubrication is not achieved.  As with a car engine, the danger usually is upon initial startup.  After the machine runs for a while, the natural heat from friction will be enough for the bearings.

One other thing I should mention is that some plastics will become brittle and can break easily at very cold temperatures.  Cast iron also becomes brittle at very low temperatures.  Some motors with cast iron frames on the North Slope are made of nodular cast iron which is a more ductile form of cast iron.

I have never been in extremely cold temperatures.   I have been in -35 F a few times but mostly I have seen a lot of -20.  Once the temperature is below 0 Deg F, it is mostly all the same.  I did go cross-country skiing once at -11 F but it was hard to stay warm.  Fortunately the work I have done with electric machinery has mostly been in a nice warm shop.

John

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April 30, 2018, 01:03:35 AM
#7
In the very cold regions, it is not uncommon to configure the engine block with a heater that is powered by AC.  Just remember to unplug the cord and you're good to start.

As mentioned, batteries lose a lot of their capabilities at low temperatures, so adding a heating pad will be useful.  Once heated to 'normal' temperature, a standard 12V car battery could provide energy for heating sensitive components.  If the use time is calculated properly, the battery will last to the end of the service day with plenty of time to recharge before the next.


Jeff

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* April 30, 2018, 02:18:31 PM
#8
Thanks again John and Jeff, battery heated pads cant say Ive heard of them but since I live in a warm environment will check them out.

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.