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From: George Jefferson on 30 Jun 2010 14:26
I have an industrial strength 12V charger. Initially it would not turn off
on battery removal. Replaced the triac and now works 95% of the time but in
some cases it still does not turn off.

The way it works: Controller triggers triac to supply charging power(from
transformer). The controller senses the voltage from the battery to
determine how to charge the battery(full charge, "trickle", etc...).

Either the controller is bad(not turning off the triac), the triac is bad,
or the circuit used is not well designed for the application(and/or designed
for a specific triac).

Again, what happens is when the cables to the battery are disconnected the
controller stays on instead of turning off as normal(and again, does not
happen most of the time).

Simply because of the sparking involved when removing the battery cables it
is obviously inductive(obviously because of the transformer). I believe
that a snubber is probably in order(not sure if the controller has one
and/or is bad/weak).

Any other obvious possibilities that I'm overlooking?

From: Jan Panteltje on 30 Jun 2010 15:05
On a sunny day (Wed, 30 Jun 2010 13:26:53 -0500) it happened "George
Jefferson" <phreon111(a)gmail.com> wrote in
<i0g28q$ori$1(a)news.eternal-september.org>:

<beep>

>Any other obvious possibilities that I'm overlooking?

Theoreticaly, at least in some circuis, it should not turn off,
because the capaciance will keep the voltage (low),
and it will try to charge.
Contributing to keeping a voltage could also be triac leakage.
Try adding a 1 kOhm resistor across the terminals.
Also try reading the manual, to see if it SHOULD turn of.

Osama
From: Grant on 30 Jun 2010 17:39
On Wed, 30 Jun 2010 13:26:53 -0500, "George Jefferson" <phreon111(a)gmail.com> wrote:

>I have an industrial strength 12V charger. Initially it would not turn off
>on battery removal. Replaced the triac and now works 95% of the time but in
>some cases it still does not turn off.
>
>The way it works: Controller triggers triac to supply charging power(from
>transformer). The controller senses the voltage from the battery to
>determine how to charge the battery(full charge, "trickle", etc...).
>
>Either the controller is bad(not turning off the triac), the triac is bad,
>or the circuit used is not well designed for the application(and/or designed
>for a specific triac).
>
>Again, what happens is when the cables to the battery are disconnected the
>controller stays on instead of turning off as normal(and again, does not
>happen most of the time).
>
>Simply because of the sparking involved when removing the battery cables it
>is obviously inductive(obviously because of the transformer). I believe
>that a snubber is probably in order(not sure if the controller has one
>and/or is bad/weak).
>
>Any other obvious possibilities that I'm overlooking?

One is supposed to turn off the power before disconnecting battery to
avoid sparks which my ignite the explosive hydrogen given off during
charging.

Try Jan's suggestion, but I'd use a lower value resistor, maybe 220 or
less, to quench any snubber circuitry.

Grant.
--
http://bugs.id.au/
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