Controller cooling

[Peter.Bridge]

So my 48v 15amp controller is in a little bag behind the saddle. I have already drilled some holes in the bag for ventilation purposes because I guessed it might get very hot.
Anyway, today in my jaunts round the tiny back roads in the North York Moors, after lots of 10% , 15%, 20% and even 25% inclines, I was cycling up a steep long hill and lost power just before the crest. I touched the controller and it was extremely hot, like it had come out of a very hot oven (I also touched the hub, which was luke warm). I moved it out of the bag and took some photos of the lovely views and it cooled down and I put it back in the bag and all worked fine for the rest of the ride. This was lots of riding at full power up long steep hills at relatively slow speeds. Should I attempt to keep the controller cooler somehow or just stop, admire the view and carry on after a few minutes ?

 

[Nealh]

It sounds very typical of any controller when riding slowly up hill, the heat inside is generated by the mosfets and once they reach their max critcal temp they short out until cooled again. As noticed the controller would have been like hot spud and one if holding it would suffer 2nd degree burns.
When I had similar issues with my 6 fet KT's it was always on the S/Downs and riding similar slow steeper inclines .
My first attempt to illeviate the issue was by glueing on extra heat sinks when that didn't solve it , I opted for a pair of 5v pc fans run off a sperate 2p 1s battery for it's power but in the end found it a pfaff. My final solution which prooved to be the best option was to simply upgrade controller to a 9 mosfet KT which had larger heat sfc area and better mosfet heat ability.

I found once a controller suffer from thermal cut out then it often also becomes easier for it to do so under similar conditions, although an inanimate component I wonder if after each heat seuence the fets become that little bit weaker each time and degrades a little.

 

[Benjahmin]

I've had similar issues with an Ezee controller, don't know how many fets it has. However, this one's metal case is actually bolted to a flat metal plate on the underside of the rear rack and it still gets too hot to hold. It only cuts out on long climbs in very warm weather but it does seem to show that it's the nature of the beast.
You are drawing high current through enclosed electronics, there's bound to be heat.
I try to keep uphill speed to a minimum of 8mph to keep the hub motor within a better efficiency range - it helps.
If your bike is a mid drive then change down a gear or two to keep motor revs up.

 

[lenny]

 

[Peter.Bridge]

I have installed a sophisticated air cooling system



See how that works out

 

[saneagle]

So my 48v 15amp controller is in a little bag behind the saddle. I have already drilled some holes in the bag for ventilation purposes because I guessed it might get very hot.
Anyway, today in my jaunts round the tiny back roads in the North York Moors, after lots of 10% , 15%, 20% and even 25% inclines, I was cycling up a steep long hill and lost power just before the crest. I touched the controller and it was extremely hot, like it had come out of a very hot oven (I also touched the hub, which was luke warm). I moved it out of the bag and took some photos of the lovely views and it cooled down and I put it back in the bag and all worked fine for the rest of the ride. This was lots of riding at full power up long steep hills at relatively slow speeds. Should I attempt to keep the controller cooler somehow or just stop, admire the view and carry on after a few minutes ?

It sounds like your motor is too fast for your rides, so it's drawing maximum current all the time. Which motor is it? What is its maximum RPM (written on it) and what voltage are you running it at?

 

[Peter.Bridge]

It sounds like your motor is too fast for your rides, so it's drawing maximum current all the time. Which motor is it? What is its maximum RPM (written on it) and what voltage are you running it at?

It's a bafang g020.500.dc.12 in a 26 inch wheel