Yes, all EV contractors of any size need an economizer. Tesla uses a proper 2-stage driver instead of a freewheel diode so they can pull the contactor in FAST and transition to a PWM drive to keep the hold power low, then disconnect the recirculating MOSFET so they can discharge the coil FAST. You don't want fixed freewheeling diodes across your coil if you ever expect to break a load, as it will cause the coil to release slowly.
Yes, you absolutely cannot just connect the coils to 12v, they will burn up. On Thu, Aug 15, 2024 at 5:06 PM Alan Arrison via EV <ev@lists.evdl.org> wrote: > I was wondering if most EV's keep chargers connected to pack full time. > > I want mine disconnected unless charging so that there is no pack > voltage outside the battery box (charger is in the cab). > > I have the DC fast charge contactors from a Tesla Model 3. They seem to > be custom made by Gigavac. > > They have isolated auxiliary contacts which I can use to enable the > charger only when the pack is connected. > > However, the coil resistance is only 1.2 ohms! At 12 volts each coil > would draw 10A and dissipate 120W! What is the deal here? > > Why such a low resistance? They must be using an "economizer" circuit > right? > > Thanks, Al > > _______________________________________________ > Address messages to ev@lists.evdl.org > No other addresses in TO and CC fields > HELP: http://www.evdl.org/help/ > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20240816/6c554238/attachment.htm> _______________________________________________ Address messages to ev@lists.evdl.org No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
