Wood Frame Battery & Controller Case - heat question

[Cookie Monster]

I'm close to finished with a wood battery frame case, more pictures to come. My goal was to have a more secure waterproof case than the standard frame bag. Plus I wanted to fit the controller inside for a cleaner look. It will be stained black and some waterproofing sealent added.

But I'm worried about heat the controller will give off on the cedar wood. These are early pictures and don't show the air flow holes I put in the box. Two 1" holes in the front for air intake and one 1" hole in the back by the controller for air flow exit. I am also using these holes for controls and motor wires. This open side will be covered with a wood and will have a small door that opens to get in for charging.

My question, do you think the air flow through would be sufficient to keep the controller from getting too hot? I guess testing will be the only true tell (it's kind of a tight fit). I am thinking about cutting out a section on the top, above the controller, for a heatsink but would rather not if it's not needed.

10t mac 500w
52v 18ah cellman triangle battery
12fet
Pushing a max of 1100 peak watts, sustained out put is around 400w.

 

[voodoosand]

Looks great!

What frame size of Ogre is that?
I ask because I have a 20" Karate Monkey and want to get that exact battery, which looks surprisingly small in the photo.

Also what is the 3rd attachment point on the downtube? I assume 2 are the bottle cage mounts.

I can't answer your question, but my guess is that it would be fine if you could be sure the two intakes are bringing in a good amount of air. I have a 6 fet that I keep in this bag http://www.timbuk2.com/tb2/products/goody_box with wires, and it survived 98F summer days without melting the waterproof liner, using a 36V battery and about 30 min of 100% (25A) throttle.

Can you move the controller more forward, maybe directly over one of the intake holes?

 

[Jolly Jumper]

I like wood cases for ebike had self one on my 1st ebike but with OSB3 more stronger and easyer to build.

Why you not just do a test ride without holes and open in after half emty and maybe on the end of battery hold your hand on the controller if you could hold it longer than 10 secounds its good.
Holes in it make just problems when you come in rain.
Wood have relatively good heat transfair.

 

[Cookie Monster]

Looks great!

What frame size of Ogre is that?
I ask because I have a 20" Karate Monkey and want to get that exact battery, which looks surprisingly small in the photo.

Also what is the 3rd attachment point on the downtube? I assume 2 are the bottle cage mounts.

I can't answer your question, but my guess is that it would be fine if you could be sure the two intakes are bringing in a good amount of air. I have a 6 fet that I keep in this bag http://www.timbuk2.com/tb2/products/goody_box with wires, and it survived 98F summer days without melting the waterproof liner, using a 36V battery and about 30 min of 100% (25A) throttle.

Can you move the controller more forward, maybe directly over one of the intake holes?

I have a 20" Ogre. I can't move the controller up because of the battery, it's a tight fit. (Cellman's battery is quite small for the watts you get, I am happy with it). I thought that putting the exit hole in the back by the controller would force air to flow by the controller either way. I think that most wood has a burning point of +450 ferinheight, but having everything enclosed was scary, so I put in the holes. Plus I can use them to run the wires, seemed logical.

The Ogre has a 3 attachment points on the downtube and 2 on the seat post. I assume it's for more bottle holder options? It surprised me, I didn't know there was 3, but I guess it helps secure the frame better.

I'll post some more pictures tomorrow, it should be finished then. Tonight is Dave Chappelle stand up in Seattle =]

 

[dogman dan]

No telling where you are, but in my desert climate that controller would fry.

Vent holes good, but it still looks pretty tightly crammed in next to the bag. Lots of room up front though to fit in additional heat sink. Bolted to the controller at the fets, using thermal paste. Just a long bar of aluminum might be all it takes once bolted to the fets.

That's that long row of screws on the side of the controller. Make your heat sink attach there, changing the screws to longer ones.

Could you cut a hole in the wood on the top? then mount the controller into that hole, bolting the metal box to a metal piece on the top? Then you'd have heat sink outside the box, and need no vents.

 

[Mozart]

I have the same box made for my bike. I also have two big holes in the front for cabling.
Used it all summer and the batteries(12s4p hobby king lipo) were not hot at all.
Thing is, I don't have my rc controller in there.
And if I did, it would probably burn. It gets pretty hot even at the 50amp max that I'm pulling.
I would suggest that you make one side panel, (or the top one) from aluminium and
add heat transfer paste and screw the side of the fet on the controller there.
That way the whole panel will cool the controller, and you can still waterproof it.
The holes are needed to cool your battery pack as well... My pack isn't encased
so it helps to keep it cool,but yours... Of course it also depends how many amps
you're pulling... But then with the holes it's not so waterproof is it? So another
thought would be to make at least the two side panels aluminium... I'm gonna
change my battery box as well, autumn is here and with lots of rain. Haven't
choosed yet the final design though.

Teo

 

[Cookie Monster]

I've done some more updating and am fairly happy with how it turned out. I should add that I choose wood because I don't know much about other materials, so it seemed easier.

Next steps - Testing:
-Figure out heat control. If needed cut out the top portion to have the controller sticking out. Would rather be done with it but if it's necessary that seems to be the best option so far. (Thanks for the suggestion!)
-Wet conditions. May put some 1" rubber tubing about 2" in length facing downward in the hole areas to keep water from going up into the box. Or plug the holes if I do the controller thing.

 

[Cookie Monster]

I should add that I wont push more than 15-20ah (1100 watts peak) and I live in Seattle, so it's cooler and err rainy... Hopefully that'll keep the heat down as well.

Thanks for all the suggestions!

 

[Jolly Jumper]

Looks rock solid, nice beatifull build. I wish you much fun with it.

Have u made a little drop hole on the lowest point in your box? for the eventualy incoming rain. I would also ad a rain shield before the front air hole that it not can so easily flow in ...

 

[Mozart]

Good looking box Cookie Monster, what's the width?
Mine is 16cm. Please post your rain experience
after some time.

 

[dogman dan]

Might work fine in that climate. I had a feeling your concern about water meant you didn't live in drought like I do.

Put some kind of louver over the holes, position holes so front ones get wind pressure, and air flows out the back holes. Then try to position that controller so the bag doesn't smother the air flow around it. Use something to maintain an air space between the controller and the bag. Just positioning the controller more forward may help.

 

[shock]

Thing about controllers is the hotter they get , the less efficient they run , the less efficient they run, the more heat they generate, the more heat they generate...

I think you see where this is going.

In my experience it is imperative that the controller heatsinks see good airflow for maximum lifespan and range. If you constructed the box out of aluminum and bolted the controller to it, that would probably work ok because of the thermal properties of aluminum. Wood does not have desirable thermal properties for interior mounting of a controller.

 

[shock]

Its too bad the box was not made with a little more room on the bottom of it, tat seems like it would be a decent place for the controller, as the heatsink fins would be parallel to the ground and the airflow.

 

[justlooking]

View attachment 4



View attachment 2

this would be a better layout, and you could have a hole in the bottom under the controller and maybe for 1 or 2 computer cooling fans to get the air flowing over the controller

 

[dogman dan]

Definitely, he's got to get some air flowing over that controller, or have a heatsinking method. In his climate, I think he might be fine if he just has a half inch of space so the bag doesn't smother the air flow, and then have holes front and back.

When moving, he'll get a breeze through the box. In winter though, that breeze will chill his battery.

Best compromise, is water seal the controller and mount it outside. Then put the plugs and connections inside the box. Then you have no need for holes that let water in, except for the wiring grommets that can easily be sealed. And you get a warm battery in winter that way.

 

[Cookie Monster]

That is not a bad idea moving the controller to the back. I will see if it fits. I may not do a fan, maybe an "L" shaped black pvc pipe or something similar for an intake. That would help cool the controller and let out any moisture that gets in (also I would seal up the other holes as I am worried about water).

I did a 7 mile commute in this morning with the current version, it was about 47 degrees, no rain. I couldn't get an accurate temp, but by touch the controller was not very hot. The CA said I only used about 1.6ah, about 11.5 watts/mile. So maybe at this efficiency I don't have to even worry about that much overheating. Also, at this temp wont the controller help keep the battery warmer? Is that a good thing? Maybe they'll work together and create equilibrium.

Something that has been confusing for me... switching from a 9fet (23 watts/mile) to 12fet (12.5 watts/mile), my efficiency has gone up but so has my power... Is that normal? Seems like I am getting way more power (acceleration) from the same amount of watts used. These are unaltered Cellman (Paul) controllers.

Again, thanks for all of your suggestions!

 

[Jolly Jumper]

I did a 7 mile commute in this morning with the current version, it was about 47 degrees, no rain. I couldn't get an accurate temp, but by touch the controller was not very hot. The CA said I only used about 1.6ah, about 11.5 watts/mile. So maybe at this efficiency I don't have to even worry about that much overheating. Also, at this temp wont the controller help keep the battery warmer? Is that a good thing? Maybe they'll work together and create equilibrium.

Lipo and other lithium batteries like it more in warm than cold.
Best performance they have in about 50°C 125F but it should not go over 60°C 140F

Edit: i have to add that lithium batteries above 30°C have more performance but loose cycle life.
more infos u can get here http://endless-sphere.com/forums/viewtopic.php?f=14&t=54202

 

[dogman dan]

I think you can definitely run as you are in less than 50F. No worries till next summer now. And you won't heat a controller much running that efficient.

Weather might be affecting that low number. Later you will know if you always get that good wh/mi. I never did much comparison testing with same motor same battery different controller. My tests were always similar or same controller, same battery, different motors.

I just find it hard to believe that a change in wh/mi that big didn't involve some kind of change in the ride. It's possible a weak amps controller meant you got less efficiency on starts and stops. The new one, maybe you spend less time in stalling mode, heating the motor. I found that to be the case when changing to slower motors, but others keep telling me, NO, feed your motor more power to avoid stalling and heating. Both methods seem to work.