Traic does not turn off on 12V charger

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?

Reply to
George Jefferson
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On a sunny day (Wed, 30 Jun 2010 13:26:53 -0500) it happened "George Jefferson" wrote in :

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.


Reply to
Jan Panteltje

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.


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