How to Repair a 12V battery charger?

And if they were repairing rather than throwing and change? Rediscover the pleasure of the repairs yourself. How to diagnose a problem or find spare parts? Repair itself is way to save money generally!
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Re: How to repair a 12V battery charger?




by plaed » 28/03/22, 19:42

izentrop wrote:
plaede wrote: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



Thank you very much for this return, it corresponds well to what I had understood!

But I had asked myself an additional question (probably too many?): should I also connect the 2 black wires together? I understand from your return that this is not necessary.
I will use a domino to make these connections as you suggested, which will also make it easier to attach to the charger frame.
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Re: How to repair a 12V battery charger?




by izentrop » 29/03/22, 01:37

plaede wrote: do you also have to connect the 2 black wires together? I understand from your feedback that this is not necessary.
It would be especially stupid, because connected by the wafer in 6 V, but not in 12 V or the rectifying circuits are logically in series.
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Re: How to repair a 12V battery charger?




by plaed » 29/03/22, 21:10

izentrop wrote:It would be especially stupid, because connected by the wafer in 6 V, but not in 12 V or the rectifying circuits are logically in series.


Thank you for confirmation ; I asked myself the question because I did not know if, on the selenium rectifier, the 2 legs on which the black wires were fixed were not connected by the axis of the rectifier.

So I replaced the diodes with the new ones, apparently without any problem since I measure the following voltages with crocodile clips:
- at 6 V: the values ​​of 5,89 then 6,17 then 6,58 then 6,97 respectively on positions 1 to 4,
- at 12 V: the values ​​of 11,6 then 12,22 then 12,85 then 13,80.

On the other hand, by charging the battery, I do not measure any current in series between the red crocodile clip and the + terminal of the battery.
If the battery is already charged, is this normal?

Out of curiosity, I also measured the resistances of a diode on the 6 V position: 85 ohm forward, and 7,5 kohm reverse.

Well, I wonder if everything is normal or if there is still some mystery!
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Re: How to repair a 12V battery charger?




by Obamot » 29/03/22, 21:43

As already said, drain the battery a little by connecting a 12V bulb to it...
Then put it on charge and see if it works.
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Re: How to repair a 12V battery charger?




by izentrop » 30/03/22, 00:56

plaede wrote:So I replaced the diodes with the new ones, apparently without any problem since I measure the following voltages with crocodile clips:
- at 6 V: the values ​​of 5,89 then 6,17 then 6,58 then 6,97 respectively on positions 1 to 4,
- at 12 V: the values ​​of 11,6 then 12,22 then 12,85 then 13,80.

On the other hand, by charging the battery, I do not measure any current in series between the red crocodile clip and the + terminal of the battery.
If the battery is already charged, is this normal?
Yes, if in position 13.8 V the voltage across the terminals of the charging battery also displays 13.8 V

You should try with a battery displaying a voltage lower than 12 V before connecting it to the charger.
Out of curiosity, I also measured the resistances of a diode on the 6 V position: 85 ohm forward, and 7,5 kohm reverse.
It depends on the multimeter. The correct measurement is in the diode position.
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Re: How to repair a 12V battery charger?




by plaed » 31/03/22, 22:29

I think I finally achieved my goal.
After having partially discharged the battery in 2 evenings, from 13.58 V to 10.88 V, I first failed to measure a charge current with a multimeter between the red crocodile clip and the + terminal of the battery in several attempts, then to the 2nd attempt to connect the red crocodile plug directly to the battery, the needle of the ammeter finally started moving (not on the 1st connection attempt, however).
The needle rises a little high, however, even in position 1 where it oscillates between 6 and 7 A at the very beginning, then seems to gradually drop by one amp in 5 to 10 minutes.
Attached to illustrate a photo of the replaced diodes, and of the front of the charger at the start of the charge.

The battery charge seems to go pretty fast at first (going from 10.88 to 11.2 in 5 mins).

What do you think ?

For my part, all my thanks for the patience and dedication of the 3 main contributors!
This is a good action in favor of sustainable development!
Attachments
Charge.jpg
start load
diodes.jpg
new diodes
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Re: How to repair a 12V battery charger?




by gegyx » 31/03/22, 22:53

Have you thought before, to redo the levels in distilled water?
Recharging a battery with a low intensity current, for example 4 A, is a longer operation. Charging a high capacity battery can take up to 20 hours. But we still advise you to use a low current, because it is safer. The operation will not damage the battery.

You can perform a simple calculation. As a general rule, a battery must be recharged with a current of an intensity equal to 10% of its capacity. In other words, the most common battery, the capacity of which is 45 Ah, must be recharged with a current with an intensity of 4 A. In this case, how long should the battery be recharged? The battery should not be charged for more than 10 hours. But we recommend that you check the charger indicator.

With a charger for regulating the intensity of the current, a large battery (65-70 Ah) can for example be fully charged in 10 hours by a current of an intensity of 8,5 A. We recommend that you consult the equipment charge indicator to prevent overcharging the battery or overheating, which could irreparably damage the battery.

https://www.vulco.fr/tips-and-tricks/ho ... ttery.html

If you recharge too quickly, and therefore leave longer than necessary, it is necessary to leave the 6 caps of the cells open (release of hydrogen)
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Re: How to repair a 12V battery charger?




by Obamot » 31/03/22, 23:12

plaede wrote: you say?
Well done ! Congratulation ! Great perseverance at work and follow-up..

plaede wrote:The needle rises a little high, however, even in position 1 where it oscillates between 6 and 7 A at the very beginning, then seems to gradually drop by one amp in 5 to 10 minutes.
It's completely normal, the same with mine which has a very practical function, a button on which you press and which momentarily moves the needle, I don't know what it can be used for except just to check "that something is going well” and at the beginning it goes up a lot, but towards the end, almost not : Mrgreen: : Mrgreen: : Mrgreen: it's good for a near zero like me : Mrgreen: ... well, I still installed RIAA preamps with toroidal transformers, filters for loudspeakers, and the connection routine for a recording studio:
basically "I know how to weld” and burn a circuit like everyone else Image : Mrgreen:
Last edited by Obamot the 31 / 03 / 22, 23: 23, 2 edited once.
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Re: How to repair a 12V battery charger?




by izentrop » 31/03/22, 23:19

Congratulations!
plaede wrote:After partially discharging the battery in 2 evenings, from 13.58 V to 10.88 V
Do not let it discharge so low, at 10.6 V the battery is dead, if it stays in this state for a long time https://www.courroie-distribution.fr/bl ... ang%C3%A9e.
plaede wrote:The needle rises a little high however, even in position 1 where it oscillates between 6 and 7 A at the very beginning
The diodes that you put are safe, but the transformer may heat up if it lasts too long.

What voltage do you get at the end of the charge? If it's 13.8 V as before, don't worry, it's the floating voltage and since the current isn't filtered, it's better to stop there.
On the car, charging stops at 14.4V, 15V max.
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Re: How to repair a 12V battery charger?




by gegyx » 31/03/22, 23:31

If empty, the maximum voltage is 13.8V, it will be difficult for the battery to rise to 14.4V.

**
Normally the charge regulator on a car should never exceed 14.5V, otherwise replacement (diodes)
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