How to Repair a 12V battery charger?

[plaed]

You can connect the battery without worries.
What you are measuring is the average rectified voltage. The battery will charge at the peak voltage which will be 13.18/ 0,9 = 14.6 V in position 4, the maximum voltage where charging must be stopped for a car battery https://fr.wikiversity.org/wiki/Redress ... phas%C3%A9.

The charging current may not rise very high due to the forward resistance of the diodes being too high. In this case, the load may drag on and the replacement of the diodes will be a necessity.

So I'll give it a try by hooking up a battery.

Is there an interest in measuring the charging current, and for that must it be done at the battery terminals during charging?

During rectified voltage measurements, both at 6V and at 12V, the needle of the ammeter does not move one iota. Does this mean that the current has very little intensity? Could this be the result of too high resistance of the diodes?

[Obamot]

Very well then!

Yes I will try to charge to see, by making pointings, with regular measurements, to check if the charge is constant and that everything is going well.

Finally it also depends on the state of the battery the regularity. This is why it would be good to make measurements of the charging current, separately from the measurements on the battery terminals. That's how I would do.

[phil59]

A multimeter, goes in series to measure the intensity, not on the plus and the minus, directly ....

[Obamot]

Oh yes indeed So you already have the answer to your question

[izentrop]

Is there an interest in measuring the charging current, and for that must it be done at the battery terminals during charging?

It is the ammeter of the charger which indicates it and follow the indications of the notice written on the front breakdown-troubleshooting-repair/how-to-repair-a-12v-battery-charger-t12822-10.html#p493206

[plaed]

Is there an interest in measuring the charging current, and for that must it be done at the battery terminals during charging?

It is the ammeter of the charger which indicates it and follow the indications of the notice written on the front breakdown-troubleshooting-repair/how-to-repair-a-12v-battery-charger-t12822-10.html#p493206

I therefore put the battery on charge, and the ammeter of the charger does not indicate any intensity (photo attached, charger connected to the mains and maximum power setting in position 4).
Does this indicate that there is no load current and is it probably a result of the condition of the rectifier diodes having high resistance?

[izentrop]

I therefore put the battery on charge, and the ammeter of the charger does not indicate any intensity (photo attached, charger connected to the mains and maximum power setting in position 4).
Does this indicate that there is no load current and is it probably a result of the condition of the rectifier diodes having high resistance?

Yes, that agrees with the previous direct resistance measurement, the current cannot move the needle of the ammeter.
The multimeter in ammeter position, caliber 200 mA should measure less than 30 mA.

At least we are fixed on the cause, all that remains is to replace the diodes without mixing in the wires

[plaed]

I therefore put the battery on charge, and the ammeter of the charger does not indicate any intensity (photo attached, charger connected to the mains and maximum power setting in position 4).
Does this indicate that there is no load current and is it probably a result of the condition of the rectifier diodes having high resistance?

Yes, that agrees with the previous direct resistance measurement, the current cannot move the needle of the ammeter.
The multimeter in ammeter position, caliber 200 mA should measure less than 30 mA.

At least we are fixed on the cause, all that remains is to replace the diodes without mixing in the wires

I paralleled the multimeter to the back of the ammeter and measured 1.7 on the 200 gauge.

So I'm going to get the 4 necessary diodes and come back to give news when I have replaced them (without mixing my brushes !)

I should find in the previous messages the characteristics of the diodes to supply.

[izentrop]

I paralleled the multimeter to the back of the ammeter and measured 1.7 on the 200 gauge.

It is the measurement of the shunt... What would have been interesting is to measure the current with an ammeter and in series with the battery.
Otherwise for the diodes, a batch of 10 rectifier diodes 10 A for example https://fr.aliexpress.com/item/1005003188842427.html, but if you prefer French:
It's per unit + shipping https://www.conrad.fr/p/diotec-diode-de ... 0-a-556765

[plaed]

I paralleled the multimeter to the back of the ammeter and measured 1.7 on the 200 gauge.

It is the measurement of the shunt... What would have been interesting is to measure the current with an ammeter and in series with the battery.

How can I make the measurement in series: by inserting the multimeter between the + of the ammeter and the plus of the battery?