Just in the past weeks I have been working on removing and installing batteries. The key is to have non-lethal voltage as long as you can as well as avoid short circuits. When I dig into a Nissan Leaf pack (which I am now re-creating in a different configuration in my EV truck's battery box) the first thing is to break the connection between the different sub-packs so each is lower voltage than the total (380V or 2x 190V as soon as you have pulled the Service Disconnect mid-pack. When re-assembling, I deliberately leave the straps/cables that interconnect the sub-packs off until the very last moment, so I am only dealing with sets that are about 72V each. Then there are typically the exposed wire ends. If I can remove the complete cable on both ends, I do the two ends while I am holding the cable so there is no point in insulating it. If I need to attach one end (because it is going into an inaccessible location) but can't attach the other end yet, then I will wrap it in electrical tape that I can remove when I am ready to attach the cable.
When a sub-pack is still a very Lethal voltage, like the Nissan Leaf having one set that is 190V, I check to see if there is a way I can protect it (Leaf has 3 covers that go over the connections of this set, so you can still limit your exposure) or a way to break the circuit, for example removing the screws from a strap and pulling it up so it breaks the set in two separate electrical circuits. Also: never work with two or more on the pack. If one touches something on one side and the other person is working on the other side and they touch each other or both touch the same conducting object (metal battery box) then they get a nasty shock or worse. Even when working with your own two hands, keep them together so you don't straddle a high voltage. There is wisdom in the saying that when interacting with high voltage, keep one hand behind your back. Note that this advise is for when working with bare hands - I drop too many screws when I try gloves and I hate wearing them, so I always work with my bare hands - which requires me to work very careful. Also use a Voltmeter to verify that a battery is isolated and not leaking to ground (frame/enclosure) since that can still build up a nasty voltage. The only moment I do wear gardeners gloves is to protect my hands from sharp metal edges when carrying/handling heavy metal assemblies such as lifting the sub-packs. Hope this helps, Cor van de Water Chief Scientist Proxim Wireless office +1 408 383 7626 Skype: cor_van_de_water XoIP +31 87 784 1130 private: cvandewater.info http://www.proxim.com This email message (including any attachments) contains confidential and proprietary information of Proxim Wireless Corporation. If you received this message in error, please delete it and notify the sender. Any unauthorized use, disclosure, distribution, or copying of any part of this message is prohibited. -----Original Message----- From: EV [mailto:[email protected]] On Behalf Of Lee Hart via EV Sent: Tuesday, January 03, 2017 10:02 AM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Electrical Safety... Thos True wrote: > Failing to insulated the exposed wires have been known to lead to some > nasty burns (on crew and vehicle), as well as damaged batteries and > battery boxes. Hope that this helps! That reminds me. Electrical cables have some nasty surprises that can cause serious mischief. Batteries can deliver enormous short-circuit currents. If a cable does flop around and short to something, the high current makes it into an electromagnet. It can JUMP and squirm like a snake, and in the process cause other shorts and mayhem. With a high short-circuit current, the insulation can melt off a wire in seconds. Now you have a BARE wire lying across your batteries. Or, if that wire is bundled into a harness, the heat can melt the insulation off the other wires, causing more short. Now Murphy really has some fun! And let's not even think about what happens if someone used cheap non UL-listed wire with combustible insulation. Also, once a high voltage DC arc starts, it is hard to stop. It can continue to arc across an amazing distance -- many inches when there's enough molten metal and debris feeding into the arc. Also, an arc can set melt or set just about anything on fire. So it pays to be extra careful! -- "Hold my beer and watch this!" -- (script for a Youtube video for the Darwin award) -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at 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 Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
