Road testing overvolted KT controller

[anotherkiwi]

I have been using a 12S (44.4v nominative) battery for a while now around town, today was the first real world test and the 15 A 36v KT controller failed this test...

Usual road to Hendaye, 12.7 km to the factory where SWMBO works:


On the way (above image) all went well until the main hill where about 35-45 seconds in the controller cut out. I was pulling about 700 W peak, over 600 W constant. Turned controller off, turned it back on and away it went again for a few seconds. I think this was a thermal issue but can't say because the controller is in a plastic box that is screwed tight.

On the way home I turned the power down (32 tooth chainwheel instead of 42 tooth) and all went fine with a peak at 649 W but mostly around 500 W climbing back up the hill. I used 7.1 Wh/km on the way home

I will swap the controller for a 36/48v 20 A one to solve this issue.

It was a real road test, on the way I rode through a thunderstorm! Had to stop for the hail, couldn't see and couldn't feel my fingers... The wind gusts were the scary bit!

 

[Nealh]

Sounds like it got to warm being encased better airflow cooling or modding with a couple of small heatsinks & 2 x 5v 40mm mini fans would work and run them off a 1s 2p set up.
My BPM 20a lishui controller got very warm I noticed, so did mod it as above, the cells take ages to drain.

 

[anotherkiwi]

Sounds like it got to warm being encased better airflow cooling or modding a couple of small 5v 40mm mini fans would work and run them off a 1s 2p set up.
My BPM 20a lishui controller got very warm I noticed, so did mod it as above, the cells take ages to drain.

One of my projects when I move everything to the trike is to fit a REAL heat sink to the controller. When you have touched a controller that has been drawing 15 A for any length of time you realise that the cooling fins on the casing are a joke. It isn't as if you can have the controller out in the wind without doing some serious waterproofing, especially in yesterdays conditions, my bike is as clean as if it had been power washed... Air temperature in the hail storm fell to 6°C and the box is huge, it isn't as if the controller was in one of those tiny rear battery controller holders.

I am assuming that the 20 A 48v controller will have different thermal values despite being in the exact same casing?

 

[awol]

I am assuming that the 20 A 48v controller will have different thermal values despite being in the exact same casing?

My 20A KT controller is in a larger casing than my 15A KT controller.

 

[Deleted member 4366]

It isn't as if you can have the controller out in the wind without doing some serious waterproofing, especially in yesterdays conditions, my bike is as clean as if it had been power washed

Are you sure? You need to start thinking outside of the box!

 

[anotherkiwi]

I really like that build (not so keen on the colour) but I don't have a 3D printer (yet) to print a controller extension box to keep the plugs out of the rain. All ideas welcome:


For the moment I think I am going to have the controller in a box, on the boom just behind the motor and a largish aluminium heat sink on top of the controller box. That box will also have the brake light stuff in it, thinking about putting blinkers on too

On the upright I will just use the 09 bottle battery controller which has an exposed heat sink.

 

[Deleted member 4366]

You can buy a plastic project box from Ebay or Maplin. Make a cutout in one end to match the shape of where the wires come out of the controller and silicone it to the controller. Cut a hole in the other end for all the wires to come out. The box is just for the connectors. Put the lid on and mount the controller under the seat pointing downwards

 

[anotherkiwi]

An update: temperatures have dropped, I am back testing 44.4v and my controller is no longer cutting out. I guess this kind of confirms that I need a cooling system for the warmer weather. The reason I went back to 44.4v is the rather steep climbs on my new commute, as LVC is 43.8v I still have about 500 W to climb the last hill home.

I will go and see a man about some carbon fibre later today (buying epoxy and glass for a dinghy) and make a new PAS disk from that and some Finnish beech ply. It will eventually be mated with a short Miranda crank = faster spinning to match the faster RPMs.

 

[Nealh]

Mini fans for heat loss.

 

[anotherkiwi]

Mini fans for heat loss.

The controller cuts out within a range of 2°C air temperature - 8°C is OK, 10°C is too hot Yesterday afternoon it cut out when I came home with a trailer full of epoxy and glass fibre. Last night it didn't break a sweat... Still towing trailer but I must admit the fish in the bag wasn't very heavy

I have tried various controller box positions on the trike. None of them work very well, looks like a custom controller box is on the list of things to build. Up front with forced air feed over the heat sink looks like the best position, I'll try and make it look evil