Controller(?) heating issue 52V 25A (40V undervoltage)

Hi,

I've got a heating issue with a big electric "step like scooter" (I think this subforum is better for my technical questions).

I guess it is the controller : 52V 25A rated for a 1000W motor (and 52V 26AH battery)... but the controller is very small with only 6 mosfets. I openned it and there are small signs of overheating (I'm not a specialist)

Symptoms are :
cold start : 30% drop in speed/power (30km/h compared to 40+km/h on flat when everything was fine)
and a further progressive drop in speed on steep road until unbearable slow speed (10km/h).
stopping/cooling the scooter for a few minutes makes it works better again... for a while...

album of photos of the controller - I think the brown color on side of the green PCB in 2nd picture shows some overheating happened (I'm not talking about the resin on the back circuit in 4th picture).

My scooter seller is selling a replacement controller, and it seems to me to a high price (95$) and I fear the problem will come back.

My questions are :

Do the symptom match with a faulty controller ? Could it be the motor ? (shortcut in coils ?)

Should I search for a stronger controller (but I couldn't find any controller with same ratings and I'm not sure it will work with the throttle/meter) and space is limited in the deck of the scooter ?

Or should I buy the replacement ? if yes, can I improve the cooling someway to prevent another breakdown ?

Thanks a lot for your help.

There is no way for a 6-Fet Controller to handle 25A in a closed space without cooling. Also the mosfets need to be top of the line to handle it.

based on your symptoms you either need to increase cooling or reduce the current output of the controller.

Thanks, so I bought the replacement controller and I'm trying to figure out my solutions for cooling it...

First is there a way to check if it is overheating ? I can attach a cooking thermometer probe outside of the controller next to the mosfet then what would be an alarming temp ?

Should I only cool the mosfet from the outside of the controller ? or blow and suck air through the inside of the controller with 2 small fans (and find a way to cool the air in the deck) ?

Free room in the deck above the controller is 10x10x5 cm (about 4x4x2 inches).

• Fan based cooling seems dangerous because of rain - I would need waterproof air intake and strong fans

• Peltier cooling seems to consume a lot and are small I would need a specific battery and on/off switch... then the peltier module would heat the metal deck through thermal pads - maybe add an heatsink outside of the deck and also insulate the controller from the heat of deck...

• Water block and a pump + a passive heat exchanger attached above my rear wheel - I would just need to make 2 holes in the deck for the tubes and use an existing 12v or 5v input since a water pump does not consume much.

Can anyone point me to the best option ?

- the mosfet are screwed on the smaller side of the controller aluminium case, and the fins on the case won't help to have a good contact - should I sand down the controller case fins ?