What is wrong with my L ion battery charger?

[coopec43]

Recently I was given a complete set of Hitachi 18V power tools (Including a charger) Coincidentally I bought a couple more Hitachi tools (drill and impact wrench as well as another battery charger) from the local re-cycling depot.

I used both battery chargers to charge 6/7(?) batteries I now have. But the charger I got from the recycle depot stopped working. I pulled it to bits and found the fuse had blown so replaced it with an identical fuse.

I plugged the charger in (without a battery inserted) and switch it on at the power point. The fuse immediately blew.

I would like to get the charger going again as back-up provided it doesn't cost too much.

Can anyone suggest where to start looking? (I have a multi-meter)

[markcouz]

My guess would be blown thyrister at output (overheat during continuous charging of multiple batteries probably). You could trace and replace but would need some electronics experience.

[coopec43]

Originally Posted by markcouz

My guess would be blown thyrister at output (overheat during continuous charging of multiple batteries probably). You could trace and replace but would need some electronics experience.

Yes, I was continuously charging batteries so that is worth pursuing.

In the morning I think I'll examine everything very carefully to see if I can spot a blackened (molten?) wire or joint.

I wonder if it could be the transformer but that would be very easily checked with the ohmmeter?

[CharlieJ]

Is the source of AC power a modified sine wave inverter?

[coopec43]

Originally Posted by CharlieJ

Is the source of AC power a modified sine wave inverter?

No. It is just Australian mains power 240VAC.

I can buy a replacement charger for $A55 so I won't spend too much time or money on it.

There's a printed circuit board and I suspect that's where the problem is. But I will look for a short on the high voltage side. (I think Markcouz may be right when he suggests it's a thyrister(?) problem).

Thanks for your post.

[Vortec]

Ha ha, I had a funny experience the other day. I have an old Moulinex vacuum cleaner than worked intermittently. At the end it didn't work at all. I dismantled it without power on and checked brushes and commutator but all ok. I assembled in under power and suddenly it worked somehow. With a screwdriver shaft knocking on different parts I discovered a loose pin at the thyristor and after resoldering the three pins my old cleaner worked as new...