how to have a cool and waterproof controller?

[cwah]

Hello all,

After big rain, my electric bike stopped working. I couldn't figure out what was wrong and I checked all wiring and it was ok... i decided to remove the kit from the bike and heard some water noise while moving controller.

I opened it up and a whole lot of water came out of the controller box... it does seem that the box isn't waterproof at all.. It does even keep water inside!

I decided to wrap the whole controller with cellophane and with isolation tape to make sure no water would get in...

But now my controller overheat and stops after 5 mn riding.....


What's the best way to have cool and waterproof controller?

I was thinking to glue some heatsink on the top and bottom aluminium side? Maybe fix it to metal area of bike to sink out heat?

Any suggestions?

 

[e-beach]

Silicone Sealant that can take high temperatures. 500F more or less. RTV sealant should work. Might find it at a local auto parts store. Open the controller and apply to all edges of the aluminum shell and screw it back together. Also cover the screws that hold the mosfets in place. Ensconce the wires where they enter the controller. Mount it in a place where the least amount of water get on the controller.

Some people like the controller under the seat. Mine is inside the battery box I installed in my triangle with only the top exposed to wind. I have ridden in the rain on multiple occasions with no problem from the controller.

POWERBOND SILICONE CLEAR - 38G from GFS looks like it should work.

 

[cwah]

Wouldn't silicone sealant also cover heat rather than help dissipating it? I need to help the controller to cool

 

[nutnspecial]

idk that celophane or silicone @ openings should be making any temp difference.

What controller is it, and did it heat up much before?

How much are you drawing for it to overheat and what is it rated for? First rule out controller damage is not the cause of overheating?

High temp rtv is good to add to endcap gaskets and screws (there's no way that's gonna cause overheating), and I also used rubber roofing style (best to stick to rubber products) caulk to adhere from controller wire penetration to an innertube around wires and connections. I'm not planning to dunk the thing, but now i should be able to worry about other things in a downpour or bigass puddle.

 

[spinningmagnets]

If the wires that exit the controller were facing up, the rain (or splashed water) might run down the wires into the controller. No matter how well the cable bundle looks to be sealed, I would mount the controller with the wires at the bottom. That being said, perhaps drill a small hole (or two?) near the bottom of the case to allow any water that gets in to drain away faster than it is coming in.

I would be comfortable with the idea of taking the case off, and then re-assembling it with heat-resistant sealant (RTV?). To stay cool, the fins on the outside of the case need air-flow. At the normal power levels that they are listed at, you shouldn't need fans to keep it cool. If you run high and frequent amps (on a long and steep uphill?) then you might need either a larger controller (12-FET, 18-FET)? or...maybe add fans. Either way, putting it inside a bag is bad for cooling. Even with fans (in a bag), the air inside the bag would get hot fast.

Maybe investigate water-proof sprays that are non-conductive and heat-resistant? report back if you find any good ones (like the red spray used to water-proof the insides of motors?)

 

[Alan B]

Conformal coat the PC board to protect it against a little water inside,
mount with wires exiting down,
have a drain hole at the lowest point,
and seal the top well.

 

[cwah]

Thanks for your kind advice. The controller is this one:
https://bmsbattery.com/ebike-kit/667-s12sh-800w-35a-torque-simulation-sine-wave-controller-ebike-kit.html

I'm repairing it here:
http://endless-sphere.com/forums/viewtopic.php?f=2&t=69488

So if I understand it correctly:
- Conformal coat the board:
http://www.amazon.co.uk/CONFORMAL-COATING-ACRYLIC-6130004030-AMBERSIL/dp/B007YGZJPO/ref=sr_1_2?ie=UTF8&qid=1431844191&sr=8-2&keywords=Conformal

- Seal the exit, wiring, screw side (don't know where to get the red spray is):
http://www.amazon.co.uk/V-tech-Black-Silicone-Instant-Gasket/dp/B00442NWOQ/ref=sr_1_2?ie=UTF8&qid=1431844253&sr=8-2&keywords=RTv+sealant

- Maybe add heatsink to the controller?
http://www.amazon.co.uk/Copper-Memory-Chipset-Heatsinks-Thermal/dp/B00KBMB76I/ref=sr_1_12?ie=UTF8&qid=1431844289&sr=8-12&keywords=heatsink

- And glue it to bike metal part?
http://www.amazon.co.uk/Thermal-Conductive-Heatsink-Adhesive-Compound/dp/B00KBNWKSQ/ref=sr_1_1?ie=UTF8&qid=1431844410&sr=8-1&keywords=heatsink+glue

- Reverse controller to have wiring on the way down

- Drill a little whole to allow water exit at the lowest point


All good?

 

[d8veh]

You don't need to do anything as complicated as that. As already said, seal the plate at the opposite end to the wires with good quality silicone sealant, then mount it vertically, so that the wires go downwards. Don't seal the bottom. If you can't mount it vertically, say 45 deg, drill a very small hole in the bottom corner so that any water that gets in will fall back out.

 

[cwah]

ok make sense. I'd like also to cool somehow the controller as I'm almost pulling 35A constant

 

[dogman dan]

No, silicone sucks. People think it's great, but really it's not. Better sealants are out there.

Look for stuff specifically for sealing rain gutters. That's the best stuff I ever touched in 30 years of construction work. Sticky as all hell, and it stays more flexible over time than silicone.

Nearly as good, caulking designed for sealing exposed windows, like pure butylene caulk. Or caulk designed for sealing things like skylight holes in a standing seam roof. Look for acetone in the caulk, not latex, water based stuff.

 

[cwah]

Dogman do you mean this one?


I've moved the controller from here:

To here of my bike:

I tapped it for now until I get the sealant. I'm going to try cycling a bit to see if it still overheat....

 

[John in CR]

The tape will just limit heat transfer.

As previously stated wires must enter from lower, because water flows along (and even inside wires as proven by Justin) wiring like a river channel. That makes a drip loop or simply having the entry of the wires lower than the rest of the controller mandatory. Keep the direction of wind and spray in mind too. Drip loops are mandatory for hubmotors too for the same reason...right up their with proper torque arms or extra strong dropouts, though less life threatening.

Then sealing is easy. Just seal the endcaps and and around the heads of the heatsink bolts.

John

 

[cwah]

Yes all of these make sense. I'd like to stealth my controller and aluminium colour isn't really stealthy at all.

Is there some paint that does good heat transfer? We have thermal paste... is there something such as thermal black paint that doesn't prevent heat to come off?

 

[dogman dan]

Uh, yeah, it does start with not putting the controller in a wet place. My favorite location is right under my ass, so when moving forward in the rain, my ass is a nice roof for it. A fender of course, to keep the tire from wetting it.

Looks to me like you use your controller, as a fender.

 

[John in CR]

Your controller shouldn't be making much heat, so dissipating it is pretty easy. You just want some fresh air getting to it. That means avoiding putting it in a box or bag, or covering it with tape that turns into an insulating layer (especially where air is trapped in the spaces between the heat sink fins. Since you're not talking about high temp, just about any paint will do, because the exterior surface to air heat transfer is so much slower than conduction of heat from the aluminum through a thin layer of paint. Where the rapid transfer of heat is important is from the mosfets to the heat spreader bar and from the heat spreader bar to the aluminum case.

For highest performance, controller color is added by anodizing the aluminum, but once you get into paint the differences aren't going to be significant enough to matter. The focus would be better spent lapping and polishing the heat spreader bar and the case where they connect, which would have far more beneficial impact.

FWIW, my favorite paint to use on ebike parts is epoxy spray paint for appliances, though colors are limited. Once cured after several days or a week, it makes for a durable gloss finish that stands up to our temp levels. My second choice is high temp enamel for engines. I've used both on motors and controllers.

 

[cal3thousand]

The problem with water is that, with time, it will seep through these seals and into the controller. The controller gets hot, air escapes and when it cools, it draws in air and possibly water, to replace the lost volume due to cooling.

To me, that means water must not allow to collect anywhere near the seams as it will be drawn in upon controller cooling. (This effect can get exacerbated if you wrap the controller such that heat will build up)

Splashing from the bottom is not really an issue, but any water that collects on the top (or bottom if mounted upside down) will have the potential to be drawn in. I had one controller, when mounted upside down, created a pool for water to collect and it was drawn in. To fix this, I put some Sugru on the portion near the seam. This prevented the water from pooling and being drawn in. I have not had any more problems with that bike and it has (surprisingly) rained some lately in LA.

 

[Punx0r]

There are two recognised approaches to protecting things from water:

1) A total hermetic seal
2) A 99% effective seal and a drain hole at the lowest point

Option one offers the best protection but is by far the most difficult to achieve and is likely to cause failure of the unit if you do not achieve that perfect seal.

 

[John in CR]

I don't recognize either of those. AFAIC it can't be sealed because the wires will act like straws for the water as the pressure inside changes with temperature, and there's no way I'm ever setting up a controller in a way that enough water can get in to make a drain hole at the lowest point effective or necessary.

Plus you left out potting it in epoxy or whatever they use for under water units.

Something I want to do some day is get rid of the controller box, and attach the heat spreader bar to a good heat sink built into the frame in a place that gets good air flow with the controller itself in the battery bay.

 

[liveforphysics]

There are two recognised approaches to protecting things from water:

1) A total hermetic seal
2) A 99% effective seal and a drain hole at the lowest point

Option one offers the best protection but is by far the most difficult to achieve and is likely to cause failure of the unit if you do not achieve that perfect seal.

Yep. Either go full hermetic, which means no stranded wires in jackets, only ceramic potted solid copper pass-throughs, and if anything gets a pinhole leak, you fill with water. You can't achieve a hermetic seal using stuff like silicone and rubber gaskets etc. Going full hermetic is kinda a stupidly difficult and costly pursuit to DIY or for mass production designs (unless you've got huge volumes for justifying large tooling budgets).

The non-hermetically sealed option works pretty well, need to have drains with tested and proven large enough drain holes actually function (drilling a pinhole doesn't typically work). Conformal coatings are critical for that approach, and in testing dozens of conformal coatings, most do little to nothing, so test whatever coating and process you're using before you trust it.

There is a 3rd option, which is my personal favorite, it adds a little weight and reduces the ability to make repairs, but in exchange can offer a real long term solution to weather related failures and improvements to thermal performance. Potting the whole controller interior volume with a thermally conductive electronics potting compound.


The way to guarantee long-term failure in humid weather is to attempt sealing, but not achieve a hermetic seal. Then you've made what is destined to become an aquarium.


ATB,
-Luke

 

[Punx0r]

I was, perhaps wrongly, including potting as hermetically sealed

I'm considering the FET spreader bar bonded to chassis, minus case, idea for a monocoque frame build. I have a gut feeling that even a steel frame will provide adequate heat sinking/dissipation for a controller with a modest heat load.

 

[dogman dan]

Too bad all controllers aren't potted inside.

Vent hole a good idea for sure, but not with a front or rear wheel splashing it. IMO, it need not be a drain per se, just a hole that hot humid air can leave through when the controller is warm, so the humidity that does condense in there does not accumulate.

In this case though, I suspect it just leaked in as liquid H2O, and couldn't drain out.

Sealing with gutter caulk or whatever could help minimize that, but a drain or vent hole that can be unsealed once in a while is a good idea. If on the flat metal surface, the aluminum tape for ducts sticks well, even in very wet conditions. And it takes some heat too. I used to tape up holes in a surfboard with it, till I could do a proper ding repair.

I suppose it's possible to tape up your controller ends with that, since it's aluminum, better than insulating cloth tape.

Nothing can truly seal the stranded wires. So put the controller where they don't get so wet. (at the plugs where the humidity can enter) Top of a rear rack, but with a open ended metal or plastic roof on it would allow parking in the rain, and covering it easier when parked. Then you can tape the shit out of the plugs to keep them at least relatively dry.

Am I the only one here that thinks finding a drier place to mount the controller is a no brainer? Seems like step one to me. All windows in a house tend to leak. It's a hole in the wall after all. But a skylight is a guaranteed leak, it's a hole in the roof! Minimize your potential to have water get in your controller and wiring plugs, by mounting it on the bike smart.

 

[e-beach]

Potting a controller electronics might keep moisture off the electronics might keep them dry, but it won't do anything about the heat buildup. It might actually contribute to the heat buildup if the epoxy transfers heat slowly. If a drain hole is added silicone if fine.

In regards to a dryer place to mount the controller well,

Some people like the controller under the seat. Mine is inside the battery box I installed in my triangle with only the top exposed to wind. I have ridden in the rain on multiple occasions with no problem from the controller.

Although I did do some editing the first day of this thread.

 

[dogman dan]

Agreed, potting might be good only for the lower powered controllers that would create minimal heat. I was really hoping to find a thin coating of potting on the E-bikekit controller when the new one came out in 2013. But alas, no.

It does have the better water resistant wiring harness, and a controller housing less prone to leaks. But in a wet climate, I'd still want that controller hiding from rain while I ride, right under my ass. The way it mounts, it gets a minimal heat sink to your bike frame. So it might work in a cool climate to bury it under tape.

One thing about the tape, it does contribute to the theft proofing. Wrap the whole frame in it for the ugly worth nothing bike look.

 

[MadRhino]

I usually install them controllers under the top tube, waterproof the top and drill a small hole to drip under. Connectors are protected with a rubber cover and hidden behind tool bags at the joint of top and seat tubes. That is enough to ride wet off road and slushy winter streets for a few years. Other connectors on the bike are protected with silicone tape, and replaced once a year as preventive maintenance.

 

[dogman dan]

Another relatively dry spot on the bike, compared to down tube, or seat tube near the crank. Currently my mud bike has it on top of the top tube. But my riding is more likely to be after the rain than during. Not a commuter, so it's never parked in the rain.



Soft rear fender added since this pic was taken, so the tire doesn't sling water to the connectors under the seat.