Surron Ultra Bee Power Stage Macro

[@EVGizmo]

They did well for what it is, and we would be shocked if not, due to the sucess they have had with the original Sur Ron

[@de-bodgery]

True...I've seen worse dsigns

[@rahulkushwaha9500]

When we put mosfets in half bridge configuration, we have to look at drain to source voltage as getting added just as when we put capacitors in series. So effectively the half bridge is rated for 200V but each mosfet is only rated at 100V. Correct me if I am wrong.

[@pingwinvonjelen6586]

no, of you activate for ex. high side, the low side will see full battery voltage on terminals - voltage drop on high side mosfet

[@de-bodgery]

The high side mosfets will see the entire pack voltage across them minus what ever little bit of drop there is from resistive losses from the motor and connectors. Every powered phase has both high side and low side mosfets on at the same time in order to power that phase. The high side mosfets will always see full pack voltage. The low side ones are so resistively close to BATT- that whatever little bit of voltage drop is across them from source to drain is about all the voltage they will see. It's not a lot....like 1v or so.

[@pingwinvonjelen6586]

both mosfets cannot be turned on at the same time, otherwise a short circuit would occur. In addition, the top and bottom see the same high voltage

[@de-bodgery]

@@pingwinvonjelen6586 Actually they can, but across 2 phases and with a motor phase between them. This is exactly how a motor phase gets powered. What should not happen is the high side and low side mosfets in any single phase get turned on all at the same time as that is what would create a dead short. Low side mosfets see the voltage drop across themselves which is quite low. High side mosfets see pack voltage they are directly in the current path from BATT+ ,through themselves, through a motor phase and finally through low side mosfets. you could build a controller with 12v low side mosfets and high side mosfets rated for 100v and still run at 82-90v. The low side mosfets would never see pack voltage. This is a dumb idea as things go wrong and you want to use all the same mosfet everywhere for proper mosfet control and consistency so you don't do this. In many BMS you will see what I'm describing. I have 32S ANT BMS with 100v mosfets in them. They are jsut switching the Batt- side so they don't really need to be 150v parts as all they see is a few volts across themselves.

[@pingwinvonjelen6586]

@@de-bodgery i don't know where you get this stuff but it's bullshit if you power up the top mosfet it becomes a very low resistance resistor, at that point you apply vbat to the phase output, the bottom mosfet is off, its source is connected to ground and its drain is connected to phase - on which the battery voltage is present, regardless of whether you have the motor connected or not. Always from the perspective of the lower mosfet you will see the full half-bridge supply voltage if the upper one is activated .

[@DistantSuns]

Excellent review. It's a shame about the potting though.

[@de-bodgery]

TEsla with the 4680 packs is using a new potting material in them. Its equally a royal pain to remove. I worked for a place that took one apart. We bought a 55 gallon drum of xylene to dissolve the potting. The entire model 3 pack went in a sealed up container to soak for a week in xylene! It worked...the potting crumbled away after that, but damn! xylene isn't nice stuff!!!

[@yehovasaso9284]

I don't know where you got 24s from because Ultra Bee got 20s (74v), the Light Bee 16s (57,6v) and Storm Bee seems to have 28s (103,6v) FYI.

[@de-bodgery]

why did they use 120v parts in it if it's jsut 20S?

[@yehovasaso9284]

Maybe bulking with som of the same parts as Storm Bee. Just a guess.

[@de-bodgery]

@@yehovasaso9284 Much of the design is similar to previous Surron controllers.