car battery charger repair?

[flat battery]

Hi reader,
I have dropped my car battery charger and it no longer works. I am getting intermittant 12Volt output readings but most of the time it is off and draining the battery instead. I think I have damaged either the ammeter or the automatic thermal overload protection device. The transformer part itself seems heavy duty so I am doubting if I damaged that.
Inside the case is the transformer with something attached to it, I am guessing 'overheat protection' then it is wired through the ammeter and a small square glazed circuit before coming out. What have I damaged? and can I disconnect the internal parts i.e. come straight from the transformer to my car battery safely? if yes, does it matter which side of the transformer is used for positive as it is unmarked?
thank you for any help as I do not like to through away items that could still be useful.
P.S. the battery itself is fine as I have charged it up while running the cars engine.

[minnie]

Hate to say this but it's probably cheaper and easier to buy a new one.

[vtech]

Hard to tell what had happened as there could be a number of things --there is a bit more involved than just a transformer.
NO, don't even attempt to hook up the transformer directly to the battery or you will melt/ burn/blowup something right away.

While it may be something simple, as minnie suggested, you may be better off buying another one as a consumer.

[Guest]

Hi,
thanks for the replies of advice. You can pick up car battery chargers quite cheaply but having looked inside the case the circuit seemed quite simple. The ammeter is no longer working. I am not sure if that alone would cause it to fail as the ammeter has only one wire into and out of it. the ammeter itself is just a cheap plastic job, like the whole charger really. manufacturer is no longer contactable for any sort of repair.

there is something about todays throw away society that I just can't fully accept! the mountains of mainly plastic waste that I shall be adding to will be all our childrens future problem, it's not the financial cost to me which is only minimal.
thanks again
stephen

[vtech]

[RODALCO]

Usually the charger has a 240/12 volts transformer inside.

The transformer produces Alternating Current which needs to be rectified first, to Direct Current with some ripple on it, to make it usefull as a charger.

At the Low Voltage side of the TX might be a fuse or thermal overload, then the bridge rectifier which is most likely to be a square black block on a heatsink with 4 legs on it. Then the ammeter.
If the ammeter is faulty (pointer bent) it should still work.

If you have a multi meter you have to do a continuity check on the ammeter and also check if the thermal overload is ok.
Then the rectifier should pass current one way and block the other way.
Also check that the TX winding is continuous.

[Guest]