Lee, perhaps you can comment on the in-panel surge protectors; if the Manzanita charger has none, would you recommend adding one to the panel or charger circuit? Even if the charger has one, adding one to the circuit or panel may give added protection for the charger (and EV) from a lightening strike?
Sent from my Kindle Fire _____________________________________________ From: Lee Hart <[email protected]> Sent: Sat Jun 15 11:10:22 CDT 2013 To: Electric Vehicle Discussion List <[email protected]> Subject: Re: [EVDL] Isolated vs non-isolated [was 100ah pack on the cheap] Peter Eckhoff wrote: > I've been listening to you all talk of isolated vs non-isolated > here... On the recharging end, I see a small Anderson connector and a > green wire which I assume is a grounding wire. If the unit is > grounded, what is the danger or dangerous act? First, recognize that safety is a relative term. Nothing is absolutely safe, or absolutely dangerous. All we can say is that some ways to do things are safer than others. Second, how a product gets used has a tremendous bearing on safety. If used carefully, even the most dangerous product won't cause injury or death. And used incorrectly, even the safest product can kill you. The Anderson connector is a standard for *isolated* DC battery charging. But it is easy to stick your finger in the opening and touch a pin. On an isolated charger, if you are grounded (other hand on grounded metal, or standing in a puddle etc.) you will NOT get a shock, because the charger's output is not referenced to ground. But Manzanita is using it for a NON-isolated charger. Here, you WILL get a shock if you touch a pin of the Anderson and ground! Manzanita says you should use their charger with a GFCI. If present, it would turn off the charger if you created a short to ground through your body. But this is not enforced; customers may not bother to use a GFCI. Other non-isolated chargers have included a built-in GFCI, to guarantee that one is present to increase safety in these circumstance. > 1) if the pack is being recharged and the case is attached to the car > frame, what should I **not** touch? What can I touch and not be in > danger? With a non-isolated charger, the EV's entire high voltage system is in effect connected to the AC power line. A high voltage exists between every point and ground. It is all too common (and dangerous) for homebuilt EVs to leave their battery terminals, and many other wiring points exposed. It is easy to touch them and ground at the same time. A non-isolated charger increases the risk of a shock. > If I can't touch a battery terminal, then that is not as dangerous Correct. The standards organizations (UL etc.) say that *if* you have a non-isolated power source, then every single wire and terminal must be completely sealed up behind safety barriers to prevent anyone from touching them. Tools must be used to take things apart to get at the terminals, and there must be interlocks so it can't be operated with the covers removed. An additional aspect is the insulation. The AC power line frequently has transient voltage spikes in excess of 1000 volts. During thunderstorms, spikes are higher even without an actual lightning strike nearby. Lightning can hit a power line a mile away, and produce thousands of volts on your house wiring. So, anything designed for the AC line needs insulation far in excess of the normal voltage. 120vac circuits are typically insulated for 1250vac; 240vac circuits to 3750vac. EV components like motors, controllers, DC/DC converters, BMS systems, etc. are not likely to have this kind of insulation. Voltage spikes on the AC line can pass right through a non-isolated charger, and appear across every component in your EV and ground. This can cause them to fail. It's possible to include surge and spike protection in the charger, even if it is not isolated. I don't know what the Manzanita chargers have for this. If Rich Rudman is tuned in, perhaps he can tell us. > 2) If the charger is plugged in and **not** recharging, what is the > danger? That depends on how the charger is turned off. If it has a physical switch, circuit breaker, or contactor that breaks both sides of the AC input, then it becomes an inert box when off. But if it only breaks one side of the AC line, or uses a solid state device that "leaks" current even when off, then the shock hazard when off is the same as when it is on. It still has voltage to ground on its outputs. Again, that's a good question for Rich to answer. -- The greatest pleasure in life is to create something that wasn't there before. -- Roy Spence -- 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) -------------- next part -------------- An HTML attachment was scrubbed... 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