I have recently had problems with my battery charger,as soon as I put it on it starts to charge very briefly then cuts right out. Having examined it I find 2 resistors have burnt out, I want to replace them but need guidance as to what number resistor to replace them with. I would appreciate any help with this problem please.Photos below hopefully will help.

 

hi NR,
What is the name /model number etc, of the charger unit.?

E

 

It is a ROADSTER 81499C

 

hi,
Is any one of these images the same as your circuit layout.?
E

https://www.google.com/search?sxsrf...AhU2QRUIHZfwBxoQjJkEegQIARAB&biw=1381&bih=873

 

Easier for me to show you pictures of the circuit layout. Thanks for trying to help I appreciate it.

 

Easier for me to show you pictures of the circuit layout. Thanks for trying to help I appreciate it.

Pictures of the bottom of the circuit board are needed to be able to help if it is possible.

 

Hope this helps.

 

Those resistors do not look “burned out” to me. Have you measured them?

Bob

 

Truthfully I do not have the experience to do that.

 

The resistors clearly got very hot, but that's not a surprise. They are 100 milliohm resistors. If they are in part of a very low resistance load they are going to get very hot.

But, if you put a meter on them or even a continuity checker and they are not open, they are not "burnt".

 

The fact that they are mounted well above the pcb surface says they are expected to get hot.

Bob

 

They tested ok,so it has to be something else that causes it to trip out. Thank you to those who tried to help I do appreciate it. Many thanks.

 

I would say at a guess looks like 0.1 ohms 3W each, they're both in parallel and are in series in the batt negative lead. So assuming it takes 10A at full each resistor would be getting 2.5W heat @5A .
Also looks like it's been repaired before there is a white link on the switch mode chip on the right.

 

Thanks for all the help, decided to give up,resoldered resistors and it still trips out so it has beaten me.