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frenchie

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  1. frenchie

    Separate Power board, tech spec controller

    You are absolutely right. But at as low switching frequencies as this board use it shouldn't be that big issue? What Fairchild SMD?
  2. frenchie

    Separate Power board, tech spec controller

    With a Wheatstone bridge I now have measured the resistance in the motor windings, thru each connection = blue-green, blue-yellow, green-yellow. Value was, as expected, the same on all connections i.e. two coils in series = 139 milli-ohm = 69.3 milli-ohm per coil. The original MOSFET IRFB3207 is suposed to have maximum RDS(on) = 4.5 milli-ohm and therefore chews up some Power. P = I2 * R Total R = 69.3 + 69.3 + 4.5 = 143 milli-ohm. The original MOSFET IRFB3207 is supposed to deliver 180A which thru the formula above leaves us 2247W per coil but, unfortunately also 146W in the component itself. This is of course "worst case" values. The truth is that the original MOSFET put in a TO-220 casing only can deliver 75A due to thin connectors. That is partly the reason Gotway doubled up by soldering a twin MOSFET in top of the original. The value on Rjunction-case is maximum 0.45 C/W for the IRFB3207. If it has been properly mounted on a heat sink that is!! This gives us 0.45 * 146 = 65.6 degrees C in worst case. In reality we might have a current As a base addition to the heat needed to get rid of that's a little too much. Kept in mind that the controller PWM-signal wont send out any different signal than before (open MOSFET is an open MOSFET, it will not send more Amps to the motor than the original setup, it just copes better with the current), the total current available is still set by the voltage/total resistance with a theoretical burst maximum at 67.2V/143milli-ohm = 469A (actually slightly higher since the max current should be calculated with the minimum total resistance, typical RDS(on) 3.6 milli-ohm = 472A). The average current is what is driving the wheel! IRFB3207 can cope with maximum burst current = 720A. The original design with only 6 MOSFET's seems to be correct. But the heat takes the better of them!! The heat sink is badly designed and much to thin where it counts. The average current might be as stated above by @lizardmech, a mere 20-30A. However; The MOSFET IRFP4368PBF has only 0.29 C/W and whats even better, RDS(on) = 1.85 milli-ohm! It also withstands a whopping 350A and as much as 195A in the connectors (TO-247AC is beefier than TO-220). Just to compare the worst case figure from the original MOSFET I use 180A again P = I2 * R Total R = 69.3 + 69.3 + 1.85 = 141 milli-ohm. Pcoil is still 2247W But the PMOSFET = 60W. And with a lower Rjunction-case at 0.29we only raise 17.4 degrees C, not 65.6! Replacing to IRFP4368PBF will be easy to cool down, sturdier current-wise and absolutely not demanding twin-MOSFET. It'll be more than enough with 6 units. That way all the other problems Gotway has completely disregarded (or just failed to calculate) when the emergency soldered twin-MOSFET's, totally vanish. For instance, the biggest no-no is the 90-degree bend immediately right next to the casing, that's not OK! Also, the twin doesn't share the same heat sink profile. That gives you different temperature per individual MOSFET and therefore a large risk of switch oscillation. The MOSFET twins running forward thru "MotoB" also just happen to be in the middle heat-wise. This also builds up a much to high temperature in general. Guess where I will mount my new MOSFET's ;0)
  3. frenchie

    Separate Power board, tech spec controller

    Too bad that's 38 pages about everything but the Gotway. But I'll search it for data...
  4. frenchie

    Separate Power board, tech spec controller

    Do you mean this Firmware-thread?
  5. Have a look at my thread on the subject; Separate Power board, tech spec controller
  6. Hi all! I have search a lot around this forum and other pages but still haven't found enough detail about the controller card of the Gotway EUC's. In particular the Msuper 3 since I'm currently working on a separate power-board with either 6 sturdier MOSFET's or 12 smaller as the original. Since most controller cards share the same basic setup I suspect that we could gather "all knowledge" in the same thread. One reason to go for 12 MOSFET's is the fact that there are components that them self may cope with currents above 360A but the connector leads stop at around 160-180A. So the first data I'm asking the forum for is Q1: Has anyone done actual measurements on the currents fed thru the motor of a Msuper 3? Preferably also an oscilloscope image... I have read a lot of documentation and can really recommend the Application Note AN-941 from where I quote the summary It is advisable to follow these general guidelines should be followed when paralleling MOSFETs: Use individual gate resistors to eliminate the risk of parasitic oscillation. Ensure that paralleled devices have a tight thermal coupling. Equalize common source inductance and reduce it to a value that does not greatly impact the total switching losses at the frequency of operation. Reduce stray inductance to values that give acceptable overshoots at the maximum operating current. Ensure the gate of the MOSFET is looking into a stiff (voltage) source with as little impedance as practical. Zener diodes in gate drive circuits may cause oscillations. When needed, they should be placed on the driver side of the gate decoupling resistor(s). Capacitors in gate drive circuits slow down switching, thereby increasing the switching unbalance between devices and may cause oscillations. Stray components are minimized by a tight layout and equalized by symmetrical position of components and routing of connections. I myself have not seen the 6 MOSFET-version of Gotways circuit boards but as I have understood the "fix" is to only solder another set on top, there's no other change of components, the impedance from the driver has been left unchanged. Also, as most of you have seen, there's no individual gate resistor, only a true parallel connection with the extra MOSFET simply mounted in the same PCB-hole. This may not be so serious depending on what frequency the PWM is operating at. Which leads med over to the next question Q2: Has anyone measured the PWM frequency of the Gotway controller board? But in general I sort of have a feeling that Gotway had a larger stock of controller cards and the add-on MOSFET is a quick fix. This is one reason they are somewhat reluctant to give hardware support and spare parts, many small re-sellers have tried and failed. It's more a question of selling new EUC's than fixing the ones that break. The plan now is, as I said initially, to build a separate power board. I de-soldered all MOSFET's along with the two 1200μF capacitors. Also all three motor-wires but realised that two of them are measured for current (the ACS709 circuit). Since there's no problem in that area at all I'll feed the current to "MotoA" and "MotoC" back to the controller PCB, keep it simple. Also, the main battery connector will be moved to the Power board, all the high currents will stay there. I will use only small signal wire connection to drive the controller card. The Power board will be mounted on the heat sink and a bigger heat sink will help balancing the heat in between the MOSFET's. Won't fit that big tunnel-thingy with a fan attached but some fan with thermostat will be used. One major drawback is that the electronics is cooled down partly by "air-speed" i.e. going slow on a hot day puts cooling to a test. The stripped controller PCB will fit nicely under the siren, it needs no additional cooling of any sort. If I get no response on the question above, I'll do some measurements o my own, just being lazy here ;0) But, please help out and collect as much electronic data as possible in this thread! Or link to other threads, I'll try to compile all data here if it seems to be spread out...
  7. Why do you love 12 MOSFET-boards so hard? What's wrong with 6 quality components but bigger? 400A each...?
  8. frenchie

    Change BT board

    That's a 6 pin HC-05. Have a look at the 4 pin HC-06 I added in my first entry: reaplacement BT board.
  9. frenchie

    Change BT board

    I know (now) that I need a resistor in series the first time so no worries from here and onward. But this wheel was bought from a private import = I have no "official" speaking partner/dealer/seller. I'll connect my oscilloscope and measure the pace of the data coming from the main board connector. Should figure out the baud rate. Then I'll try to pre-program the BT-board with that speed and see if it'll keep the setting in a non-volatile memory.
  10. frenchie

    Change BT board

    Hi all I don't know if someone here already have a topic going about the hazard of connecting the battery to main board. I was forced to leave my main board disconnected for a week which of course discharged the "main" capacitors (right next to the BT board on the Msuper 3). Then I got a real heavy recharge spike when I connected the battery again. After that the BT board no longer worked, no signal is sent from over the air. So, I found a replacement BT board and read the thread Converting the MSuper board to BT LE? by OliverH quite useful. However, I lack som basic info; What's the baudrate the main board of the Msuper 3 use towards Bluetooth? Is there a change of baud rate during initial setup? Can't see that type of commands being sent from my main board but then again, I don't know for sure if my main board survived or not. I think so since everything still works and I suspect that the HC-06 Bluetooth board might have a setting saved to it and I'm currently lacking these for now.
  11. frenchie

    V3 84V 2000Wh

    Nice job! To all you guys having second thoughts about the extra weight; don't forget to put it all into perspective. If you had 22.1kg before and 24.2kg after the difference is 9.5% extra. But if you add 75kg body weight we're talking 2.2% extra weight. (I weigh in at 99kg and then the extra 2.1kg would mean 1.7% extra). So, I wouldn't consider that as even a remote problem.
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