Transformer center tap secondary

[KevinW]

I have an older Torcan 12v battery charger that has a center tap transformer, on the secondary, one wire has 14 volts while the other has only 7.
The total output for the charger is only 11 vdc.
Should both secondary wires have 14 volts?

 

[Grossel]

Well, without knowing anything at all about that specific model that is only guesswork.

In general - if the unit is in working order it's safe to assume that the transformer also are working as intended.

 

[MaxHeadRoom78]

If the transformer does not appear to be overheating, I agree, probably normal.

 

[Diver300]

Have you measured the voltage between the 7 V end and the 14 V ? It could be that the centre-tap terminal is at one end and not in the middle.

 

[KevinW]

When I take a measurement at the leads that connect to the battery it is 11 volts like it 's splitting the difference between the 14 and 7 volts.
I would think a 12vdc, 6 amp charger should be charging a battery at 14vdc.

 

[Pommie]

Early chargers were often switchable between 6 & 12V. Is that a possibility?

Mike.

 

[KevinW]

Not switchable Mike.
It only has one diode .
The diode looks good and two resistors are also good.

 

[KevinW]

Tested the two rectifier diodes and one is .44nF while the other is .76nF.
One is 88 ohms while the other is 57 ohms.
Would that make much of a difference?
I'm now reading 14 volts on both secondary's.

 

[MaxHeadRoom78]

Tested the two rectifier diodes and one is .44nF while the other is .76nF.
One is 88 ohms while the other is 57 ohms.
Would that make much of a difference?
I'm now reading 14 volts on both secondary's.

What meter range did you use to measure the resistance?
Most modern VOM's cannot test a diode on the resistance range, only the diode test where the diode is forward biased and the volt drop is measured.

 

[KevinW]

It's just an auto setting but I should have said k ohms.

 

[MaxHeadRoom78]

You cannot measure the resistance of a diode/rectifier without passing enough forward current.
Which if the result was Kohms then that would confirm it.

 

[rjenkinsgb]

The basic transformer - rectifier power circuit is probably like this; the resistor represents whatever load it feeds.

As there is no smoothing capacitor, the output is "rough" DC and a voltmeter will show the average voltage - but the peaks will be rather higher and the battery would take current in pulses at each peak.

If you connect a suitable capacitor across the DC out side, it should allow the meter to read that peak voltage, if needed.

 

[KevinW]

You cannot measure the resistance of a diode/rectifier without passing enough forward current.
Which if the result was Kohms then that would confirm it.

With the diode test both diodes are .467 volts so they look good.
Thanks for pointing that out, new meter just learning how to use it.

Where would I install a filtering capacitor?

 

[Nigel Goodwin]

With the diode test both diodes are .467 volts so they look good.
Thanks for pointing that out, new meter just learning how to use it.

Where would I install a filtering capacitor?

Why do you want to?, simple battery chargers don't need them, and it's designed not to have one.

 

[KevinW]

I'm just trying to find out where I'm losing the 3 volts from the output.

 

[Nigel Goodwin]

I'm just trying to find out where I'm losing the 3 volts from the output.

What makes you think you are? - presumably you're also measuring that incorrectly? (although to be fair it's not simple to measure with a meter).

What are you trying to do?, doesn't it work?.

 

[KevinW]

The output is 11 vdc, it was 14vdc a couple of years ago.
I don't think a 12vdc battery will fully charge at 11 volts.
I have 14vac coming from both legs on the secondary.

 

[sagor1]

Measuring 11VDC may be an average, the voltage may have higher peaks. Only a scope would show that. As an idea, try measuring the DC output with the meter in AC voltage setting, it may show the pulse (peak) voltage, but averaged out as well unfortunately.

 

[KevinW]

6.14ac on the battery clips.

 

[KevinW]

There is one other component, c32fx99, 7052s
I can't locate any information on it. If it's a diode , it's bad.
May be an scr.