Dui ni shuo de dui
10 kW
flippy said:the internal resistance adds up with current. this is why you get massive heatsinks on say for example a cpu or graphics card. those thave billions of mosfets running at hundreds of amps. gross simplfication but shit adds up when you push dozens of amps.
Yeah, sure, but switching is actually a huge part of the heat generation on a CPU. In a BMS during discharge, there should be no switching as long as everything works fine and you don't go over one of the 3 limits I've mentionned before.
parabellum said:Your BMS is very similar but not same, theoreticaly you should have worse fets if going linear on V ratings but they could potentially be better fets if they are some original reputable make.
Do you have access to fet sink? (the balance sink is apposite one)
What is different on your BMS? Do you have a link?
There is one sink (actually just an aluminum plate) on each side of the BMS. One is for the balance board, the other for the FETs. So two sinks in total.
flippy said:What is the max temp you did see at discharge? (the app shows temp at discharge, I believe)
It was barely above the ambient temperature after a 55km ride.
Ambient temp was around 36-39 degrees (it is terribly hot here these days), BMS was around 42 if I remember correctly.
That's why I say that heating shouldn't really be much of a concern, it just doesn't heat.
One thing to note though is that my BMS is outside of my battery. It has its own 3D printed box with cooling holes. But I doubt this makes for a really huge difference, maybe it would heat 2-3 degree C more in a sealed enclosure? Pretty sure it is not game changing.
flippy said:How long(seconds in average)you are over 120A?
I'm over 120A battery draw from 25km/h to the top speed (120km/h). So pretty much everytime I hit the throttle. Of course at stabilized speeds this rating drops down a lot. A few figures at stabilized speeds for your reference:
-18A @ 50km/h
-30A @ 70km/h
-80A @ 100km/h
-about 120A @ top speed.
A few figures during full acceleration:
-50A from 0-10km/h (starting current)
-90A from 10-25km/h
-120 from 20-30 km/h
-150 from 30-40 km/h
-180 from 40-50 km/h
-200-210 from 50-100km/h
Then it progressively goes down to 120A until max speed (120km/h)
My start current is a bit low but unfortunately I don't know if this can be changed on my sabvoton controller
I have a tendency to go really heavy on the throttle, more than anyone I know, so I run at max acceleration most of the time, unless of course if the road is too crowded. To answer your question, I'd say that my motorbike is capable of doing the 0-100km/h in 6 or 7 seconds. So the BMS has to support that kind of load for maybe 90% of this time.
flippy said:Not confronting your experiences, just need data to understand the whole picture.
Sure, I have absolutely no problem with that . Ask any question you want, I'll be glad to answer if I can.
If you want me to make a particular test for you or to confirm some figures don't hesitate. I was a bit hesitating too when I bought this BMS (seemed too good to be true to me) so I totally understand. The only thing I've not tested yet it the bluetooth app, I'll hopefully be able to check it this evening.