I've found that the largest issue when the resistor fries is that it deposits carbon dust all over the place. The BMS in those packs is *very* picky about leakage currents and will fault with an isolation fault if you sneeze near the exposed board. When the resistor fries it soots up the board, even sometimes within the internal layers of the 4 layer board. This really sucks to try to fix. I've had the resistor fry on one car and I did replace it but still I had isolation faults. I ended up being one of the very last people to get a warranty claim on the board and get it replaced. I know that some people have successfully repaired boards by changing the resistor and thoroughly cleaning the board. Currently I've got a few bad MLEC boards (the board with the resistor on it) and a few good ones (shhhh!) Another issue is that the resistor is close by to ribbon cables. More than one person has had the ribbon cable get toasted.
People have discussed moving the resistor somewhere else. Care would have to be taken to not cause any inadvertent isolation faults though. It really is picky. I don't think it'd work to put the resistor outside the pack as it would be likely to get junk on it and then cause an isolation fault. Maybe it could be moved within the pack and maybe even be larger. But, all of that is a real pain to do too. The easiest approach is likely the addition of a time delay circuit on the heater. On Thu, Dec 22, 2016 at 1:16 PM, Cor van de Water via EV <[email protected]> wrote: > The heater is on high voltage, so it has its own (small) contactor. > To avoid the software glitch that accidentally continues to power the > heater, which causes the pre-charge resistor to blow, there are two ways > to avoid this fatal flaw: > - add a small circuit in the pre-heater contactor coil loop, so that > even if the SW accidentally brain-farts and leaves it on, the added > circuit has a time-delay after seeing the ignition turned on and will > not engage the heater until a couple seconds after the car has actually > started. > - or cut one of the legs off that pre-charge resistor and wire it > outside of the controller to a well-accessible location where a blowing > pre-charge resistor might be a nuisance, but a quick swap can be made an > be back on your way, instead of the scrapnel destroying the circuit > board... > Of course, this only works with not-yet-damaged boards. > I'd be interested in inspecting the board of a disabled Think City to > see if I can get it going again, they seem to be fun little cars. > > Cor van de Water > Chief Scientist > Proxim Wireless > > office +1 408 383 7626 Skype: cor_van_de_water > XoIP +31 87 784 1130 private: cvandewater.info > > http://www.proxim.com > > This email message (including any attachments) contains confidential and > proprietary information of Proxim Wireless Corporation. If you received > this message in error, please delete it and notify the sender. Any > unauthorized use, disclosure, distribution, or copying of any part of > this message is prohibited. > > > -----Original Message----- > From: EV [mailto:[email protected]] On Behalf Of damon henry via > EV > Sent: Thursday, December 22, 2016 7:23 AM > To: Robert Bruninga; Electric Vehicle Discussion List > Subject: Re: [EVDL] Sequence of Events contactors > > There is no standard way of handling startup, so to say "most" is a bit > misleading. What you describe certainly does not fit the sequence of > either of my two OEM hybrids, nor does it match my two DIY EVs. There > is no definitive answer to the question posted. > > > Perhaps a better question needs to be asked. Something a bit more > specific. For instance, I am planning on converting an ICE to an EV. > What is a safe startup sequence to power on my 12 volt and traction > circuits and what components are required? Even then, more details are > better, for instance do you have a DC-DC converter, and what kind of > motor controller are you using. > > > Damon > > ________________________________ > From: EV <[email protected]> on behalf of Robert Bruninga via EV > <[email protected]> > Sent: Thursday, December 22, 2016 7:10:20 AM > To: Electric Vehicle Discussion List > Subject: Re: [EVDL] Sequence of Events contactors > > Most EVs and Hybrids have at least three contactors. The sequence is: > * Close One battery lead and check for leakage > * Drop that relay and close the other lead with a series resistor and > check for leaks > * Bring the first one back in to power up still via the series resistor > for a few milliseconds to allow the car system to charge all capacitors > * If still no smoke, pull in a main contactor to bypass the resistor. > > You can hear the relay dance in any Prius or most other EV's. > > There should be NO heavy loads until all of the above are complete. A > software glitch in the THINK CITY made the mistake of leaving the 4 kW > heater possibly on, so that on the third step above, the 4kW is trying > to > go through a 5W 47 ohm resistor and it blows up. This kills the car, > and > all replacement b0oards are gone, most cannot be repaired, and so the > company is out of business and there are lots of THINK CITY's just > gathering dust. > > Bob, WB4aPR > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Read EVAngel's EV News at http://evdl.org/evln/ > Please discuss EV drag racing at NEDRA > (http://groups.yahoo.com/group/NEDRA) > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20161222/f0df > de3a/attachment.htm> > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Read EVAngel's EV News at http://evdl.org/evln/ > Please discuss EV drag racing at NEDRA > (http://groups.yahoo.com/group/NEDRA) > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Read EVAngel's EV News at http://evdl.org/evln/ > Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
