OT anyone know anything about battery chargers ???

It is true that some 'smart' chargers have no output until they are connected to a discharged battery - they sense the polarity they're hooked to and won't try reverse charging if hooked up backwards.

This charger isn't that smart - but another possibility that happens with these a lot is the power cord plug end gets stressed and there's nothing going to the charger chassis. Sometimes you can determine that by wiggling the cord at the plug end and see if the charger hums or the ammeter jumps (presuming the charger is connected to a battery). Something easier check and fix than digging into the guts of the beast on a wild goose chase.

Stu

"Only those who risk going too far can possibly find out how far they can go." (T.S. Elliot)
 
Every handy man would benefit from having some sort of VOM, also known as as volt-ohm-milliameter for
times like this. I like the old style analog meters with the D-Arsonval movement but a digital tester would work too of course.
You can set the meter to AC volts of an appropriate scale and check the outlet the charger is plugged into. You could also follow the
wires to the transformer and test at the primary wires of the transformer. (Be sure the unit is turned on to charge to do this). If you don't
get a line voltage reading, then the problem is from the primary wiring to the outlet plug. Suspect would be the plug, the cord, the overload
circuit breaker, the switch. That's about it for the primary side. If you have line voltage at the primary side, then the problem is likely on
the secondary side. It is quite unlikely that the transformer is defective, although possible . To test on the secondary side of the transformer,
put the test leads on the secondary and look for a voltage of somewhere in the 15 to 20 volt range using the meter set to AC volts.
These heavy secondary wires go to the rectifier diodes. At this point one could unplug the charger and test the diodes with the VOM using a
medium resistance scale. A good diode would conduct one way but have a relatively high resistance the other way. They can be tested in circuit.
There isn't much left at this point if the diodes test OK. Set the meter on DC volts( maybe 25 or so) and plug the charger in and have it
turned on. Apply the leads to the efferent side of the diodes and check to see if there is DC voltage there. If there is, about the only thing
left to test is the charge indicator meter, the output wires going to the charger clips and the connection of those wires to the charger clips. A lot of times, rusty wiring connections can be the problem like on the meter on the charger or elsewhere. The meter has full current going through it so if the
connections on it or if the meter itself failed, there would be no output at the clips.

There is a little more to that Schumacher charger I see because it has a switch to charge at various levels meaning the secondary
of the transformer probably has several taps on it to switch in various voltage levels to the battery being charged but the above all applies.
One other thing comes to mind, the circuit breaker could be on either the primary or secondary side of the circuit I suppose.

Just a couple of caveats:

1. Follow the general safety precautions so you don't shock yourself.
2. Be absolutely sure your test meter is set to what you are intending to test if using an analog meter.
Not following this can fry the D-Arsonval movement in the meter rendering it junk.


This old style charger is easy to diagnose and repair. To the contrary, the new light weight(so called smart) chargers with the switching
power supplies are much more complex and no where near as dependable. Personally, I would not own one of those.


Sorry this got so long but I think I covered most of the details to diagnose a simple transformer type battery charger.
 
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Did your neighbor loan you a broke charger knowing you’d fix it for him :xmaslights:did he say it worked
Maybe yours has the same problem
 
benmychree said:
I have hear that some chargers have no output when there is no input (fully dead battery) try it on a battery that is not dead.
Click to expand...

Many chargers will not turn on if the battery is completely discharged. This is not a fault; it is by design. If the battery to be charged is completely dead then you can get the charger to function if you jump the terminals with another 12 volt source. Hook up the leads from the charger to a battery and use another battery or a 12 volt power supply to provide power momentarily to the poles of the battery and the charger will usually turn on.

I do this all the time when I use my charger to power an electrolytic bath. I would try this before I tore into something that someone kindly loaned me.
 
Poor design philosophy in my opinion- here's why: leave a battery pack long enough and it goes completely flat even if there is nothing wrong with it. How is your typical non-technical user supposed to charge it? How does the charger know that there is nothing wrong with it? They need to have a "charge the freaking thing anyhow" override button.
I ran into this on one of my brother's cordless drill chargers- Ryobi I think- drove me nuts till I figured out what was going on- he was ready to throw it away!
Mark
 
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