If you use an in-the -breaker box, 20 amp GFCI breaker it will be made to open at high current. Probably work longer than you own the car for. Subject: Re: [EVDL] Voltage sensing shut off switch
Thanks Lee, This is just the type of solution I was hoping to find. I have no plans to add a BMS to my calb cells on my motorcycle. I can see that this presents the most danger for me during charging. I currently charge on a timer, so that even if I forget I'm charging the timer saves me, but I notice that when these cells get full they are done in a hurry. So after watching the end of charge multiple times I have decided that there is a very safe and noticeable pack voltage that indicates there really is no reason to keep charging. In my case it is right at about 54.5 volts. The pack will charge at 54 volts for quite a while, then slowly climb to around 54.5 volts. After that, cells start taking off on in a hurry. With my emeter, it is pretty easy to know how long to set the timer and how many amps to set the charger at to get a nice refill, but the voltage shutoff is perfect for any small errors in judgement I might make. I plan on fitting this all into a nice small package th at I can take with me when I want so I never have to worry about getting distracted. My 12 hour spring wound timer died, and they did not have another one at Home Depot so I bought one of these instead. http://www.homedepot.com/p/Belkin-WeMo-Switch-F7C027fc/203536127 I actually think it is pretty handy. If I have one of those "Oh no did I leave my charger on" moments I can shut it off remotely from anywhere with my cell phone. It also has a built in countdown timer that I use, although it is a lot more work to open an app on my phone and go through a settings menu to set the timer than turning a single knob :) i ended up just setting my timer for 90 minutes, then I adjust my current on my charger. For charging I have my longtime favorite Shumacher SE-1072 plugged into one of those cheap Chinese 15 amp variacs. I use the variac for fine control of the charging current. For the kit I am putting together I will get another 12 hour spring wound count down timer. That along with the GFCI plug and voltage sensing circuit should make a nice package. damon > Date: Wed, 24 Jun 2015 10:56:59 -0500 > From: [email protected] > To: [email protected]; [email protected] > Subject: Re: [EVDL] Voltage sensing shut off switch > > damon henry via EV wrote: > > Has anyone ever made a circuit to shut off a switch once a > > predetermined voltage limit has been hit while charging. I would > > love to work on something small that is easy to carry. It would > > plug directly into a standard Nema 15 120 volt 15 amp receptacle and > > have it's own Nema 15 receptacle for a charger to plug into. It > > would have a voltage sensing input I could use to monitor my pack > > voltage and once a predetermined voltage limit was hit, the circuit > > would open and latch so that the charger stopped charging until > > everything was manually reset. I'm sure there are a million simple > > ways to get this done. > > Yes; this is indeed an easy problem to solve. :-) > > Charge your EV with an extension cord with a built-in GFCI (Ground > Fault Circuit Interrupter). Or, put a GFCI in an outlet box with a > male plug on the back and the female socket (that's part of the GFCI) on the front. > > The circuit that senses pack voltage will generate a ground fault, > which orders the GFCI to turn off. It looks like this (here comes some > bad old ASCII art -- view it with a fixed-width font like Courier): > > pack+___. . . ____/\/\___ . . . . . . . . . . . . . . . > . . . . \/\/\/ | . R2. . | . . . . . . . . . . . . . . . > . R1 1K . ^ . .| . 1K. ._|_/ D1 one or more zener diodes that > . trimpot |____|. . . .//_\ . . add up to a few volts less your > . to adjust voltage . . .|. . . desired turn-off voltage > . where it switches . . .|_ . . . . . . . > . . . . . . . . . . . . . _|. K1 a small relay with a > . . . . . . . . . . . . . _|. 5-12vdc, 10-20ma coil. It > . . . . . . . . . . . . . _|. will pull in at about 2-5vdc. > pack-____________________| > > AC hot_____/\/\____||____AC ground > . . . . . . R3 . . || > . . . . . . 10K. . K1's normally-open contact > > The dots are just there to keep smart-alec email programs from > replacing multiple spaces with a single space. If you can't figure out > how to view anything with a fixed-width font, the circuit is very > simple. It's a trimpot R1, a fixed resistor R2, a zener D1, and a > relay coil K1 all in series. When the pack reaches the desired > shut-off voltage, the zener conducts, current flows in the relay coil, > and it pulls in. The normally-open contact of K1 closes, connecting R3 from AC hot to ground. > This creates a ground fault, and the GFCI turns off! > > -- > The greatest pleasure in life is to create something that wasn't there > before. -- Roy Spence > -- > Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150624/984d4fa2 /attachment.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)
