Since the charging sequence has a fixed order of control, it should be possible to avoid one vehicle's isolation check to fault the other one. The "sending" vehicle can do the isolation check before the charging is started, while contactors are still open, then the connection is made, then the receiving EV does the isolation check at a moment that the sending EV is not checking and since both packs are isolated, all should check out fine, no? Cor.
On Mon, Oct 25, 2021 at 3:54 PM (-Phil-) via EV <ev@lists.evdl.org> wrote: > > Thanks Lee, But keep in mind without galvanic isolation on this, (or > vehicle support from the manufacturers) it would likely instantly trip the > HV isolation detection on one or both EVs. So the magnetics have to handle > the full power being transferred, not just the difference. > > Basically the isolation check circuitry on one vehicle is going to trigger > the opposite's. I have also run into this when paralleling 2 EV packs > (Tesla). > > -Phil > https://youtube.com/ingineerix/ > > > On Mon, Oct 25, 2021 at 10:01 AM Lee Hart <leeah...@earthlink.net> wrote: > > > (-Phil-) via EV wrote: > > > Don't believe everything you read! Definitely not possible to do this > > > without some sort of high-power buck/boost converter in-between the EVs. > > > Even a 50kW capable unit is going to probably weigh 50lbs minimum even if > > > built very well. > > > > Hi Phil, > > > > Forgive me for butting in, but that's not quite the case. The > > power-handling ability of the DC/DC is determined by the *difference* in > > voltage between the two packs, times the current being transferred. > > > > It works the same as a buck-boost transformer. Suppose you want to buck > > 240vac down to 220vac at 50 amps. The transformer doesn't need to be > > 240v x 50a = 12KW -- it only needs a 240vac primary, and a (240-220) = > > 20vac x 50a secondary. This secondary is connected in series with the > > primary, and phased to "buck" the voltage down 20 volts. That's only 1KW > > -- 12 times smaller. > > > > Similarly, the DC/DC needed to transfer power between two EV packs that > > are nominally the same voltage only needs to handle the *difference* in > > voltage between them, times the current. > > > > Of course, the real challenge is to handle the battery management needed > > during such a charge. The EV already has the necessary fans, fusing, > > balancing, and state-of-charge controls; but convincing the EV's > > computers to help do this would be a bigger problem than the charging > > itself. > > > > Best wishes, > > Lee Hart > > > > -- > > A designer knows he has achieved perfection not when there is > > nothing left to add, but when there is nothing left to take away. > > -- Antoine de Saint Exupery > > -- > > Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com > > > > -- > > This email has been checked for viruses by Avast antivirus software. > > https://www.avast.com/antivirus > > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20211025/b53fbb91/attachment.html> > _______________________________________________ > Address messages to ev@lists.evdl.org > No other addresses in TO and CC fields > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > ARCHIVE: http://www.evdl.org/archive/ > LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org _______________________________________________ Address messages to ev@lists.evdl.org No other addresses in TO and CC fields UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/ LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org
