How to Repair a 12V battery charger?

[plaed]

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

All my confusion, I probably offered some bullshit , and reformulates: should the multimeter be inserted between the clamp of the red wire of the charger, and the + terminal of the battery?

[izentrop]

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

All my confusion, I probably offered some bullshit , and reformulates: should the multimeter be inserted between the clamp of the red wire of the charger, and the + terminal of the battery?

Yes, but one test to do without a multimeter, in the 12 V position, is to put the crocodile clips in contact for a short time.

If the ammeter of the charger deviates at more than 4 A, the charger works and you should not insist at the risk of burning it, but I rather think that it deviated little and will confirm the fault of the diodes.

[plaed]

Yes, but one test to do without a multimeter, in the 12 V position, is to put the crocodile clips in contact for a short time.

If the ammeter of the charger deviates at more than 4 A, the charger works and you should not insist at the risk of burning it, but I rather think that it deviated little and will confirm the fault of the diodes.

Hello,

the brief contact test between the crocodile clips gives a few sparks but the needle of the ammeter on the charger does not move.

On the other hand, by inserting the multimeter between the red clamp of the charger and the + terminal of the battery, I measure a value between 160 mA and greater than the caliber (200 mA) depending on the position of the charge intensity selector on the charger ( 160 in position 1, 170 in position 2, then greater than the caliber in positions 3 and 4).
By switching to caliber 10A the multimeter remains at zero, which I cannot explain.

Anyway I'm going to get the diodes and a domino.

[Obamot]

Here some leads from someone who makes battery chargers himself

It gives values...

[plaed]

Here some leads from someone who makes battery chargers himself

It gives values...

Interesting indeed!

maybe my battery itself is very little discharged, which could also explain that the charging current is low.

[Obamot]

Well, just plug in a 12V lamp for 24 hours to discharge it...

But without wanting to be categorical, I think the charging current should stay the same right? It's like filling a tank with a hose, the flow remains the same until the tank is full!

[izentrop]

Yes, but one test to do without a multimeter, in the 12 V position, is to put the crocodile clips in contact for a short time.

If the ammeter of the charger deviates at more than 4 A, the charger works and you should not insist at the risk of burning it, but I rather think that it deviated little and will confirm the fault of the diodes.

Hello,

the brief contact test between the crocodile clips gives a few sparks but the needle of the ammeter on the charger does not move.

On the other hand, by inserting the multimeter between the red clamp of the charger and the + terminal of the battery, I measure a value between 160 mA and greater than the caliber (200 mA) depending on the position of the charge intensity selector on the charger ( 160 in position 1, 170 in position 2, then greater than the caliber in positions 3 and 4).

The current of 170 mA confirms the too high direct resistance measurement of the diodes measured previously.

By switching to caliber 10A the multimeter remains at zero, which I cannot explain.

The measurement should have given 0.16A. Perhaps you forgot to connect the red lead to the 10 A terminal of the multimeter?
Where did you order?

If you don't want to have to monitor the charge, you can put this kind of module which automatically disconnects the charger as soon as the battery is full https://fr.aliexpress.com/premium/-XH%25252dM601.html

[plaed]

Perhaps you forgot to connect the red lead to the 10 A terminal of the multimeter?
Where did you order?

For the measurement, however, I was careful, just modified the caliber on the multimeter and replaced the end of the red lead on the + terminal of the battery (the black lead being on the crocodile clip of the charger).

For the diodes I was taken from a bad inspiration, wanting to make work the small local trade and to obtain them immediately, and took a hell of a socket, 3,50 € each!
Moreover, it is not exactly the model you recommended, they are 45 V 20 A (exact ref. V20A45Y M844A)...

[plaed]

I ask myself an additional question before proceeding with the connection of the diodes and all the cables on the domino (I take a 2x6 positions).
Should the 2 black cables of the + be connected, the one coming from the ammeter, and the one coming from the red jumper to select the supply voltage?
Or are they already elsewhere?

[izentrop]

Should the 2 black cables of the + be connected, the one coming from the ammeter, and the one coming from the red jumper to select the supply voltage?
Or are they already elsewhere?

It is necessary to remove the wires connected to the selenium rectifier and connect them to the corresponding diodes.
The top black wire connected to the cathodes of the 2 top diodes (reference)
The other 2 wires are connected to the 2 anodes of these diodes.

The black wire of the lower stage connected to the cathodes of the 2 diodes at the bottom
and therefore the wires remaining to be connected to the anodes of these diodes.

I hope the drawing is clear enough, the red lines represent the wire cuts