DaveThomasPilot Posted December 12, 2017 Share Posted December 12, 2017 Maybe this belongs in the "Mods, Repairs, & DIY" forum, but I thought I'd start here. I'm going to get either a 16s or a Tesla. I really like the idea of the higher voltage--assuming the control board designer knows what he's doing and used FETS with a sufficiently higher voltage specification. I worry, since there have been reports of FET failures. Could it be they are using the same FETS as in 67 volt boards? A higher voltage breakdown specification means either a higher Rdson ( on resistance), or a bigger (and more expensive) die. Bigger die have higher gate capacitance, and are harder to drive. Higher switching losses could result if the gate driver isn't scaled appropriately. Inexperienced power conversion designers sometimes chase low RDSon to minimize conduction losses in the FETS, and compromise reliability with a insufficient voltage margin. Has anyone seen a P/N on the FETs when their wheel was apart? It would be nice to check the specs on the FETS they are using. Otherwise, I'll go with the KingSong and avoid the higher voltage wheels until they have proven reliability. Failures should be in parts per million, not in the low percentage points. Otherwise, the problem is likely a design issue. Link to comment Share on other sites More sharing options...
Marty Backe Posted December 13, 2017 Share Posted December 13, 2017 5 hours ago, DaveThomasPilot said: Maybe this belongs in the "Mods, Repairs, & DIY" forum, but I thought I'd start here. I'm going to get either a 16s or a Tesla. I really like the idea of the higher voltage--assuming the control board designer knows what he's doing and used FETS with a sufficiently higher voltage specification. I worry, since there have been reports of FET failures. Could it be they are using the same FETS as in 67 volt boards? A higher voltage breakdown specification means either a higher Rdson ( on resistance), or a bigger (and more expensive) die. Bigger die have higher gate capacitance, and are harder to drive. Higher switching losses could result if the gate driver isn't scaled appropriately. Inexperienced power conversion designers sometimes chase low RDSon to minimize conduction losses in the FETS, and compromise reliability with a insufficient voltage margin. Has anyone seen a P/N on the FETs when their wheel was apart? It would be nice to check the specs on the FETS they are using. Otherwise, I'll go with the KingSong and avoid the higher voltage wheels until they have proven reliability. Failures should be in parts per million, not in the low percentage points. Otherwise, the problem is likely a design issue. I'll leave the technical discussion to others. I can say that over 1500-miles on five different 84-volt Gotway wheels, I have had no MOSFET failure. Anecdotal I know, but there you have it. In my opinion the 84-volt wheels have been proven reliable. Hell, it's kind of old news now. Were you aware that the new KingSong 18L is an 84-volt wheel? All the 84-volt wheels have more oomph (very technical term) than any 67-volt wheel that I've ridden. Join the club, you'll have a blast - maybe that was a poor choice of words Link to comment Share on other sites More sharing options...
Bryan Wells Posted December 15, 2017 Share Posted December 15, 2017 I vote 84v also Link to comment Share on other sites More sharing options...
esaj Posted December 23, 2017 Share Posted December 23, 2017 You likely got your answer already from elsewhere in the forums, but from what I know, the Gotways use IRFB4110 (TO-220) and IRFP4110 (TO-247): https://www.infineon.com/dgdl/irfb4110pbf.pdf?fileId=5546d462533600a401535615a9571e0b https://www.infineon.com/dgdl/irfp4110pbf.pdf?fileId=5546d462533600a4015356290ec51ffe Both are 100V, and (I think) pretty identical, except the TO-247 can of course shed heat better due to larger case. KS16S uses IRFP4368, 75V, TO-247: https://www.infineon.com/dgdl/irfp4368pbf.pdf?fileId=5546d462533600a40153562c61512015 Link to comment Share on other sites More sharing options...
dmethvin Posted December 23, 2017 Share Posted December 23, 2017 On 12/12/2017 at 11:34 PM, Marty Backe said: All the 84-volt wheels have more oomph (very technical term) than any 67-volt wheel that I've ridden. For our international members familiar with other units, an Oomph is about about 2.6 Moxies or 3.1 Giddyups but only about 0.29 Holyshits. Link to comment Share on other sites More sharing options...
Marty Backe Posted December 24, 2017 Share Posted December 24, 2017 2 hours ago, dmethvin said: For our international members familiar with other units, an Oomph is about about 2.6 Moxies or 3.1 Giddyups but only about 0.29 Holyshits. Link to comment Share on other sites More sharing options...
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