Painting the controller

I know there will be opinions on this. I have a rather simply built, non innovative albeit with decent quality parts, home made e-bike. One thing I would like to do is paint the controller black so it doesn't stick out like a sore thumb. Will that make it run a lot hotter?

painting it flat black will make it run cooler actually

Unless the paint is thick and provides insulation or it's sat in the sun

Unless you have baking sun I would not hesitate to paint it whatever colour you want

Agreed, just no "thick" coatings.

Anodize is the ideal solution but anything else will do just fine imo... specially considering how you have it mounted. 8)

It's unanimous. Thin coat of satin black it is. (anodized black would be cool but it's definitely not a show bike so Krylon from Home Depot it will be.) I'm excited just in time for the Spring riding season.

I'm pumping up to 10,000 watts through my 18 FET Lyen controller painted black. No heating problems here.

As Flathill said, black paint would make it radiate heat better. But it will also absorb heat from the sun faster, so I don't know that there is any real value to it. What I do know is 4 of my controllers have been black. 2 anodized, and 2 painted. None have ever had a problem, and I mount them in the same place you do on a couple of bikes.

I thought colors only were supposed to make a difference in heat absorbtion, and only from something within the light spectrum? Of course, our 'light spectrum' may not be fully comprehensive.

Anyway, just searching to see opinions on painting. I'm getting ready to use HF bedliner on my racks . . . and controllers? Yeah it's a little thicker and a poly coating, but it should be ok.

Look up black-body radiation (IIRC) for how color can affect heat radiation vs absorption.

edit: here's a page that has better explanations than I would have typed up
https://physics.stackexchange.com/questions/122911/black-and-white-matters-but-why-and-how

The bedliner will be a heat-insulating blanket around your controller, blocking some of the heat from escaping the way it did without it.

Very thin paint would be much better performing.

Anodizing would be even better than paint.

(speaking from experiences with various heat-producing objects over the years, and how I improved them or made them worse).

You can do a rigorous scientific experiment (with controls) to test these if you like.


Different "colors" / compositions of surface treatments will radiate or absorb infrared in different amounts; probably most of them will radiate or absorb heat better than polished metal would (possibly better than the burnished silver of a typical ebike controller), as it doesnt' matter what the visible light color is (it's not radiating in visible spectrum, just infrared...unless it's way past "serious malfunction" ).

So even if it was anodized white, it'd probably still shed heat better than if it was plastidipped black.

Thanks brother it's going on 5am here and I'm blasting some tunes and getting ready to paint. Perfect balance. Of kinda wasted. . lol.

Anyway, I'll read thru it again but I came to the conclusion that black body radiation is a bit too theoretical and thus untrustworthy for my purposes.

The bedliner will be a heat-insulating blanket around your controller, blocking some of the heat from escaping the way it did without it.

Very thin paint would be much better performing.

Anodizing would be even better than paint.

Click to expand...

But I do agree with that. I don't think it'll be an issue. I don't think these cheap 18fet controllers (30$) are programmed to run hot). I probably just don't understand the minds behind the theoretical/'scientific' aspects as far as the relation between light and heat (and color)?

If the heat in the controller is from sitting in direct sunlight, then painting it black will absorb heat (like a DIY solar collector). The heat is coming from the components inside, so a single coat of paint won't help, but...I don't think it will hurt, either. Get a digital barbeque thermometer with remote probe and attach it to the controller case on the hot parts (FETs)...make a few runs like you normally do to establish a baseline temp. Then paint it any way you like, and repeat the heat runs.

Personally, I cringe at the thought of needing to wash mud off of a controller, even if I have personally managed the water-proofing efforts. Maybe consider covering it up with a black shroud, and then using two fans to flow air across it? (one pushing, one pulling). Just a thought...

Please see Dr Bass recommendation of Krylon 1602 in the "Definitive Tests on the Heating and Cooling of Hub Motor" thread.

Applied as one element of hub cooling experiment here.

Used this to paint my Phaserunner heatsink (although without the oven-baking heat curing step)...