Is this about the traction pack relay of a Prius? I once saw a plot of a set of measurements taken on a "Classic" (NHW-11) pack for voltage and current while driving. The current swing went from 60A draw to 50A charge and voltage was around 290V with about 60V swing mostly depending on current, but also SoC. So from that you can conclude that 50A is about the rating of that contactor as Lee already indicated and it never needs to interrupt more than about 600A in a short circuit due to approx 1/2 Ohm internal resistance of the 276V 7Ah pack. Those may be decent ratings for the electric assist or for an extrememly light non-freeway vehicle, but if you plan a freeway capable vehicle this will not be sufficient for the current draw by the propulsion that you will see in such a vehicle. Using the Prius relays for the pre-charge or to control heater, Airco, DC/DC or other auxiliary devices connected to the pack can be a good application. Hope this clarifies,
Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Lee Hart Sent: Saturday, April 06, 2013 12:28 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Main contactor secondary contactor use?? On 4/5/2013 12:53 PM, Ds2inc wrote: > Hi lee! > > So would this, and pardon my ignorance there are still some tech > aspects of this I haven't been able to fully logic out for all the > variances, not be a good main for my system? Would it be an > acceptable secondary? > > Ate you familiar with this product I can't find specs any where! It is a Toyota part, probably custom built to their specs. Toyota doesn't publish specs, and you are unlikely to find them anywhere else unless the manufacturer also sells a similar version on the open market customers. I have one of these contactors as a spare part for our Prius. Judging from its physical size, I doubt if it can carry more than 50 amps continuous. It might be able to carry 100 amps for a minute or less, and can probably switch a couple hundred amps *ONCE* on an emergency basis. That would be adequate for accessory loads (heater, charger, DC/DC converter, etc.) but not for the main controller. Your main contactor (the one that cuts power to the motor controller) is there for two reasons. First, because your controller still draws power even when it is not running the motor. Without a main contactor, you'd find your pack would run dead in a month or so just from the controller's power. Second, it's there for SAFETY. Motor controllers can fail *ON*. The car can take off all by itself (unintended acceleration). So, you want a contactor that can be turned off no matter what, to guarantee that the car will stop. To do this, the contactor needs to be able to break the worst-case peak current that the batteries can deliver. This can easily be 500 to 1000 amps! A properly chosen contactor can do this safely. It may arc like crazy and destroy its contacts in the process -- but it WILL open! -- The most dangerous enemy of a better solution is an existing one that is just good enough. -- Eric S. Raymond -- Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use 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 For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
