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
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