I'm not convinced that 'equipotential bonding' is the right solution. The first question to ask about a piece of accessible metalwork is 'Could it become live?' This is not new: it has been applied to metal trim on the outside of plastic TV cabinets for many years. It's so highly improbable that it can safely be left isolated. So a good solution for the cars is to apply reinforced insulation to the live parts, so that all accessible metal has a vanishingly low probability of ever becoming live. With best wishes DESIGN IT IN! OOO - Own Opinions Only <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England Sylvae in aeternum manent. From: Ken Javor [mailto:[email protected]] Sent: 18 July 2017 23:20 To: [email protected] Subject: Re: [PSES] Solar electric cars built by college students Not commenting on the safety standard issue because not knowledgeable, but it is interesting to note that many conventional ICE-powered cars with 12 Vdc electrical systems don't bother to bond all metallic parts of a car together. It used to be that all you need to do to ground something was attach it to nearby metal structure; that is no longer the case. There are dedicated ground lugs on the car in various places that are available, but if you don't use them, there is no guarantee that the metal you are connecting to has a low resistance path back to the battery negative terminal. On car using batteries with lethal potentials, it will be necessary just like for ac mains-powered appliances that any metal accessible to people driving or working on the cars have a low resistance bond back to ground potential, and when charging the car, the ground reference for the ac charging potential also connects to the car ground. And in case of a crash, it would be real nice if the class H bonds lasted long enough for the battery to somehow disable itself...
Using now archaic military aerospace jargon, modern ICE-powered cars with 12 Vdc electrical systems have (MIL-B-5087) class C (current-carrying) bonds only where they need them and no need to implement class H (hazard) bonds. An electric car with lethal battery potential will have class C bonds where they need them, and class H bonds everywhere. Ken Javor Phone: (256) 650-5261 _____ From: Scott Aldous <[email protected] <mailto:[email protected]> > Reply-To: Scott Aldous <[email protected] <mailto:[email protected]> > Date: Tue, 18 Jul 2017 12:06:37 -0700 To: <[email protected] <mailto:[email protected]> > Subject: Re: [PSES] Solar electric cars built by college students UL 2202 is the UL standard for EV charging system equipment. Section 14 is on EV Bonding, and it requires the output circuit of the charger to provide a means for bonding the EV during charging for grounded system of protection. There are different protection schemes, so the need for bonding is dependent on which is applicable. In general, I would think that separate grounding of an EV from the charging system could create a ground loop and so would not be desirable. On Tue, Jul 18, 2017 at 11:11 AM, Ted Eckert <[email protected] <mailto:[email protected]> > wrote: I recommend against following Ferrari's practice. Apparently, portions of the FXX K supercar are energized to 480 V when charging. There is a fin on the roof with flashing LEDs. Red means stay away and green means safe. http://jalopnik.com/the-ferrari-fxx-k-might-electrocute-you-1796961190 <http://jalopnik.com/the-ferrari-fxx-k-might-electrocute-you-1796961190> <http://jalopnik.com/the-ferrari-fxx-k-might-electrocute-you-1796961190> Ted Eckert Microsoft Corporation The opinions expressed are my own and do not necessarily reflect those of my employer, Ferrari or the Society of Automotive Engineers. From: Dale Reid [mailto:[email protected]] Sent: Tuesday, July 18, 2017 10:52 AM To: [email protected] <mailto:[email protected]> Subject: [PSES] Solar electric cars built by college students Hello, Speaking of grounding, can someone share some thoughts on what would be the best practice regarding an earth ground for an electric car while plugged in and charging from the grid? Would it be best to tie a car's metal frame to ground while it's hooked up for a charge? Dale Reid - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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