Controller placement question

I have a pretty modest setup. 12T Mac geared hub Mac motor on the front of a bakfiets-style cargo bike that I'm building. I have a 52v battery and a 6fet 25amp controller. The whole thing only outputs about 1200 watts or so and I don't really flog it all that much, preferring to maximize my range over going fast. I almost never use throttle except for a slight assist when pulling away from a dead-stop with a heavy cargo load, and for the most part I always have PAS engaged and I use a Cycle Analyst v3.1 with the two-button switch to set about 10 varying levels of pedal assist. I the past when I had this same kit installed on another bike, I positioned the controller on top of the battery box within the main triangle of the frame. The battery is a triangle pack and I had it positioned low in the frame and the case was designed such that the controller just sat on top and the wires ran into the forward portion of the box with all the connections protected inside from the elements. That case that I made before won't fit on the new frame I'm building, so I'm designing a whole new case that will actually be rectangular. I'll have enough space inside for all the wiring connections to be organized discreetly, in addition to having a buck converter to allow me to step voltage down to some USB ports that I'll have installed on the case, for possibly charging devices from the e-bike battery on longer trips if necessary. I'm also considering using the battery case to hold some type of controller for a large solar panel at some point. The solar panel would not be for charging the e-bike battery as even a 2'x3' panel is likely to not be big enough, but instead it will be for charging other electronic devices and would only be using some space inside the battery box for the various apparatus necessary to work with the panel. I've read about how the controllers generally need airflow and should usually be mounted somewhere out in the open. However, I've also read some opinions saying that for lower output systems the controller can sit inside a bag or enclosure as long as there some modest amount of airflow. I was wondering if the controller could go inside the aluminum box I'll be fabricating *if* I include some vents for additional air flow, or am I just better off mounting it somewhere on the outside of the box so that I gets more cooling from ambient air? I can add some photos later today, but imagine a bike like a Larry vs Harry Bullitt and the battery case is installed behind the middle head tube of the bike, low in the frame with a piece of plywood in front that will somewhat restrict airflow to the battery case anyway.

Generalizations are generally generalized for the general public. While it's generally a bad idea to put a controller, a device designed to get hot, in an enclosed environment, it's sometimes perfectly fine.

You know your setup best. Did your controller ever get hot before? Do you know how hot it gets? If yours never gets very hot, it might be fine. I'd make sure it was away from the batteries, though. Batteries are murdered by heat. a bit of an air gap in the case and some ventilation should be enough protection.

I've got a bike that gave me a scar from the controller burning my ankle. I have another bike who's controller never gets hot and it's mounted inside the frame. Different bikes, different use, different power, different situation, different solution.

I hadn't actually thought about the effect of waste heat from the controller on the battery. Might be a good idea to keep the controller outside the case then. Even if it didn't get hot when it was outside the case before, being inside without the passive cooling might change that.

Welcome to the forum.

A few helpful hints to help you out. Its a good idea to follow these guidelines. It helps the reader understand, rather then skip the reading all together. Though that article link is in depth, this article is a bit better. I guess with the texting and computer age, those principles are less thought of, but again, its helpful to the reader, otherwise you get few, if any responses.

Just trying to help ya out!
:thumb:

Depends on where you live. Once its above 90F, I sure want my controller out in the air to breathe. But if its cooler where you are, just some air that circulates in the box may be enough. You might think about some kind of vents, so hotter air can breathe out the top of the box. That might be plenty in a cooler climate than the desert of the SW USA.

Most of my ebike conversions have the controller under the luggage rack, and I added silicone sealant on the boxes to prevent the splashed up water from entering.

I have one store-bought bike where the controller is in a box under the pedals. It's poorly sealed, with a hole in front for the cables. The other day, I got caught in the rain. About 1" fell in me while I was going home. I thought I dried off the bike, but the next day, it was dead.

Opened the compartment holding the controller and water ran out. Water was inside the controller too, and still sizzling before I killed the power. Amazing that it still works after I cleaned it up.