Controller Temperature

[oldie1982]

Finally got my test bike on the road.

Previously i have only ever had a Woosh SWX02 kit, never noticed the temperature of the controller as its built into the battery.

However my new setup is as follows

KT 15a controller
48v 7ah battery
36v 250w bafang hub labelled G020.250
36v Bafang - no model number but its smaller and lighter then the SWX02, - i did ask on here and someone mentioned it looks identical to a wheel in a Pendleton Sommerby e bike.

Currently my test bike has the 36v Bafang no model number wheel installed. I did about a 10 minute ride to test the bike and see the top speed (22mph). The LCD3 was displaying about 630ish watts at top speed from what i can remember.

I have the controller + wiring in a seat bag. I opened the bag up after 10 minutes and it was extremely hot, too hot to touch. This was in 25C heat.

Is the heat normal?

This might sound silly but will the smaller no name Bafang make the controller heat up quicker? Or does the size of the motor not matter at all?

 

[Nealh]

Controllers usually need airflow or a heatsink to help cooling, other wise yes if placed in a bag with no air flow heat will buid up. In the past I have made airholes if I place controller in a bag or I opt to use a larger controller for heat dispersion.

The small KT 6 fet controllers do get very hot esp with high current and slow hill climbing, thye need extra cooling or as a I have done opt for a 9 fet version to solve the issue.

 

[matthewslack]

Finally got my test bike on the road.

Previously i have only ever had a Woosh SWX02 kit, never noticed the temperature of the controller as its built into the battery.

However my new setup is as follows

KT 15a controller
48v 7ah battery
36v 250w bafang hub labelled G020.250
36v Bafang - no model number but its smaller and lighter then the SWX02, - i did ask on here and someone mentioned it looks identical to a wheel in a Pendleton Sommerby e bike.

Currently my test bike has the 36v Bafang no model number wheel installed. I did about a 10 minute ride to test the bike and see the top speed (22mph). The LCD3 was displaying about 630ish watts at top speed from what i can remember.

I have the controller + wiring in a seat bag. I opened the bag up after 10 minutes and it was extremely hot, too hot to touch. This was in 25C heat.

Is the heat normal?

This might sound silly but will the smaller no name Bafang make the controller heat up quicker? Or does the size of the motor not matter at all?

At 630 W and lets assume 90% controller efficiency, it needs to dissipate 10% of 630 = 63W. It'll get as hot as an old fashioned 60W light bulb in a bag without airflow!

 

[oldie1982]

Thanks guys

If it continues to over heat will it shut down? or cause some other damage?

 

[matthewslack]

Thanks guys

If it continues to over heat will it shut down? or cause some other damage?

Make and model dependent! Some will, some won't and hot bits then fail, mosfets in the controller for example.

I don't have direct experience of generic kit. My non-generic shimano goes into a thermal limiting condition, where it reduces output when it gets too hot.

 

[Nealh]

My KT 6 mosft 20a controller use to get so hot I couldn't touch it, it was hotter then a baked spud. Eventually the mosfet will overheat and thermally cut out an electrical short, once it has cooled it will operate again but will be weakened. The likelyhood of future issues will occur and likely at some stage the mosfet will sinply fail and short permently.
The worse thing is being enclosed so ne has to try and supply airflow.

 

[PC2017]

My Black KT cuts out at 27 degs(ambient) with airflow, once this year, normally in blazing sun, added 2x heatsinks last year with unibond sticky pads and cheapo thermal paste stopped the cutting out for that year(2021). They need repasting tbf, I might try mx4 I have some somewhere. The controller is at least 2 year old with daily use in all weathers. Tbf I have spare controllers in case, but I have not noticed any degradation.

 

[oldie1982]

I swapped the wheel to a 700c 48v SWXO2 code 11 this has stopped the over heating of the controller.

Why would this be?

Appreciate the help guys.

 

[oldie1982]

It’s a dual voltage LT 36v 48v controller.

The previous SWX02 was a 36v 250w code 13 motor.

 

[Nealh]

I swapped the wheel to a 700c 48v SWXO2 code 11 this has stopped the over heating of the controller.

Why would this be?

Appreciate the help guys.

Motor winding (rpm) is different so may be running more efficiently.

 

[Woosh]

It’s a dual voltage LT 36v 48v controller.

The previous SWX02 was a 36v 250w code 13 motor.

did I sell the SWX02 36V kit to you? 36V Code 13 runs much hotter on 48V because it does not have as much length of copper wire as 48V model (I sell both). Be careful when going uphill, 36V code 13 does not run as efficiently as 48V code 13 because it does not have as much copper wire, it runs much hotter. You can strip the gear's nylon teeth then it will be an expensive repair.

 

[PC2017]

It’s a dual voltage LT 36v 48v controller.

I realised it was a stupid question so I deleted it pml

 

[Nealh]

I just noted Tony's reply and re- read your post's. It is down to efficency between a 36v wound hub being over volted and a 48v wound hub being run at it's nominal voltage. With the 36v motor it will need internal motor cooling to prevent heat build up.
Although one can over volt hubs there is always a downside where heat build up is involved. Some use internal hub cooling to over come the short falls or one can opt for a better controller to deal with heat build up.

 

[oldie1982]

did I sell the SWX02 36V kit to you? 36V Code 13 runs much hotter on 48V because it does not have as much length of copper wire as 48V model (I sell both). Be careful when going uphill, 36V code 13 does not run as efficiently as 48V code 13 because it does not have as much copper wire, it runs much hotter. You can strip the gear's nylon teeth then it will be an expensive repair.

No I bought it from a chap who had done 100 miles. It was a 48v 700c code 11 I assume?

I just noted Tony's reply and re- read your post's. It is down to efficency between a 36v wound hub being over volted and a 48v wound hub being run at it's nominal voltage. With the 36v motor it will need internal motor cooling to prevent heat build up.
Although one can over volt hubs there is always a downside where heat build up is involved. Some use internal hub cooling to over come the short falls or one can opt for a better controller to deal with heat build up.

One thing I have noticed on the lcd8 is that the motor temperature is always 15 degrees. It never changes. Even after a long hill. Is there a setting I have which is wrong in the programming?

 

[Nealh]

Hubs don't have temp sensors so it is nothing to so with the hub, what you are seeing is ambient air temp or just a nonsense value.

 

[oldie1982]

Thanks